{"gene":"NIT2","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2009,"finding":"Rat liver Nit2 was identified as omega-amidodicarboxylate amidohydrolase (omega-amidase, EC 3.5.1.3), catalyzing hydrolysis of alpha-ketoglutaramate (the alpha-keto acid analogue of glutamine) and alpha-ketosuccinamate (the alpha-keto acid analogue of asparagine) to alpha-ketoglutarate and oxaloacetate, respectively; the enzyme is located in the cytosol and is ubiquitously expressed.","method":"Biochemical purification from rat liver cytosol, enzymatic assay with identified substrates (alpha-ketoglutaramate and alpha-ketosuccinamate), co-purification tracking","journal":"Biochimie","confidence":"High","confidence_rationale":"Tier 1 / Strong — independently replicated by two separate groups (Krasnikov et al. PMID 19595734 and Jaisson et al. PMID 19596042) using orthogonal approaches (purification from rat liver + assay; bacterial expression + purification + assay)","pmids":["19595734","19596042"],"is_preprint":false},{"year":2009,"finding":"Mouse nitrilase 2 (Nit2) expressed in E. coli and purified was shown to catalyze hydrolysis of alpha-ketoglutaramate and other known omega-amidase substrates; mouse nitrilase 1 showed no such activity, establishing Nit2 (not Nit1) as the mammalian omega-amidase.","method":"Recombinant protein expression in E. coli, enzymatic activity assay with alpha-ketoglutaramate substrate","journal":"Biochimie","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified recombinant protein, replicated across two independent laboratories in the same year","pmids":["19596042"],"is_preprint":false},{"year":2009,"finding":"Purification of omega-amidase approximately 3600-fold from rat liver cytosol using alpha-ketoglutaramate hydrolysis and succinamate hydroxaminolysis assays confirmed the enzyme's activity toward both substrates, with the ratio of activities remaining constant throughout purification, establishing these as substrates of the same enzyme (Nit2).","method":"Multi-step biochemical purification (~3600-fold) from rat liver cytosol, two independent enzymatic activity assays (alpha-ketoglutaramate hydrolysis and succinamate hydroxaminolysis) tracked in parallel","journal":"Analytical biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — rigorous multi-step purification with two independent orthogonal activity assays, consistent with independent replication by two other labs","pmids":["19464248"],"is_preprint":false},{"year":2007,"finding":"Human NIT2 protein is distributed mainly in the cytosol; ectopic overexpression of Nit2 in HeLa cells inhibits cell growth through G2 arrest (not apoptosis); Nit2 overexpression up-regulates 14-3-3sigma (an inhibitor of G2/M progression and Akt-activated growth) and down-regulates 14-3-3beta.","method":"Subcellular fractionation, ectopic overexpression in HeLa cells, flow cytometric cell cycle analysis, proteomic and RT-PCR analyses of downstream effectors","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple orthogonal methods (fractionation, flow cytometry, proteomics, RT-PCR) but no mechanistic reconstitution of the pathway","pmids":["17488281"],"is_preprint":false},{"year":2012,"finding":"Human Nit2/omega-amidase has a catalytic triad of E43, K112, and C153; site-directed mutagenesis of each residue (E43A, K112A, C153A) impaired catalytic activity; deletion of loop 116-128 also disrupted substrate binding and turnover; molecular dynamics simulations confirmed the role of these residues in substrate specificity toward alpha-ketoglutaramate and succinamate.","method":"Site-directed mutagenesis of active-site residues, kinetic activity assays with alpha-ketoglutaramate and succinamate substrates, molecular dynamics simulation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro mutagenesis combined with kinetic assays and structural modeling in a single rigorous study","pmids":["22674578"],"is_preprint":false},{"year":2013,"finding":"Crystal structures of yeast Nit2 (a homolog of mammalian Nit1, not Nit2) in complex with alpha-ketoglutarate and oxaloacetate revealed that these products are covalently bound to the catalytic Cys169 via a thioester bond, reflecting reaction intermediates; this provided structural insights into the catalytic mechanism of the Nit subfamily. Notably, alpha-ketoglutaramate is a relatively poor substrate for yeast Nit2, distinguishing it from mammalian Nit2.","method":"X-ray crystallography of wild-type and C169S mutant enzyme-intermediate complexes, enzymatic activity assay","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — high-quality structural data with mutagenesis but performed on yeast Nit2 (homolog of mammalian Nit1), single study; informative for understanding mammalian Nit2 mechanism by comparison","pmids":["23897470"],"is_preprint":false},{"year":2021,"finding":"QM/MM computational study of Nit2 established the catalytic mechanism involves four steps: (1) nucleophilic attack of Cys191 on alpha-ketosuccinamate, (2) formation of a first tetrahedral intermediate (rate-limiting step, calculated barrier 18.4 kcal/mol consistent with experimental kcat), (3) formation of a second tetrahedral intermediate, and (4) hydrolysis of a thioacyl-enzyme intermediate to release oxaloacetate; Cys191 and Glu81 play active catalytic roles while Lys150 plays a secondary role.","method":"QM/MM computational simulation validated against experimental kcat values","journal":"Chemphyschem","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational study only, though validated against experimental kcat; no new wet-lab experiments performed","pmids":["33463886"],"is_preprint":false},{"year":2024,"finding":"NIT2 interacts physically with bromodomain-containing protein BRD1 to inhibit HBO1-mediated acetylation of histone H3 at lysine-14 (H3K14ac) and suppress RELA-targeted oxidative phosphorylation (OXPHOS) gene expression, independent of its metabolic (omega-amidase) function; Src kinase phosphorylates NIT2 at Y49, promoting NIT2 dissociation from BRD1 and subsequent binding to E3 ligase CCNB1IP1, leading to autophagic degradation of NIT2; reduced NIT2 protein levels allow BRD1 to form phase separation and increase H3K14ac, and also stabilize RELA by suppressing ING4-mediated RELA ubiquitination.","method":"CRISPR-Cas9 screen, Co-IP, patient-derived organoids, xenograft tumors, phosphorylation assay, phase separation assay, ubiquitination assay","journal":"Science translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (CRISPR screen, Co-IP, phosphorylation mapping, phase separation, xenograft) from a single lab; mechanistic complexity not independently replicated","pmids":["39565874"],"is_preprint":false},{"year":2024,"finding":"Reversible oxidation of specific cysteine residue(s) in NIT2 by H2O2 inhibits its catalytic activity; endothelial-specific knockout of NIT2 in mice leads to increased alpha-ketoglutaramate (αKGM) levels and impaired angiogenesis, with knockout cells showing impaired proliferation, sprouting, and induced senescence, establishing NIT2 as a redox-sensitive enzyme linking glutamine catabolism to endothelial function.","method":"Endothelial-specific NIT2 knockout mice, metabolomic measurement of αKGM, H2O2 treatment with activity assay, endothelial cell sprouting and proliferation assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockout with metabolic phenotype plus in vitro redox-inhibition experiment; preprint, single lab, not peer-reviewed","pmids":["bio_10.1101_2024.08.28.610061"],"is_preprint":true},{"year":2026,"finding":"NAT10 (the only known ac4C transferase) promotes NIT2 mRNA stability through ac4C modification, increasing NIT2 expression and thereby enhancing glutamine metabolism (glutamine consumption, alpha-ketoglutarate and ATP production) in lung cancer cells; overexpression of NIT2 rescued the suppression of cell viability, proliferation, migration, and glutamine metabolism caused by NAT10 knockdown.","method":"Methylated RNA immunoprecipitation (meRIP), dual-luciferase reporter assay, RNA interference, overexpression rescue, xenograft model, metabolic assays","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — meRIP directly measures ac4C modification on NIT2 mRNA, rescue experiments performed, single lab","pmids":["42030693"],"is_preprint":false}],"current_model":"Human/mammalian NIT2 is a cytosolic omega-amidase (EC 3.5.1.3) that catalyzes the hydrolysis of alpha-ketoglutaramate and alpha-ketosuccinamate (the alpha-keto acid analogues of glutamine and asparagine, respectively) to alpha-ketoglutarate and oxaloacetate via a Cys-Glu-Lys catalytic triad (C153/C191, E43/E81, K112/K150 in human/Nit2 numbering), linking transamination reactions to the TCA cycle; its catalytic cysteine is redox-sensitive (inhibited by H2O2), making it a metabolic redox switch in endothelial glutamine catabolism; NIT2 also has a non-enzymatic 'moonlighting' function in which it binds BRD1 to suppress HBO1-mediated H3K14 acetylation and RELA-driven oxidative phosphorylation gene expression, with Src-mediated phosphorylation at Y49 triggering its autophagic degradation via CCNB1IP1 and promoting chemoresistance in gastric cancer; NIT2 expression is post-transcriptionally regulated by NAT10-mediated ac4C modification stabilizing its mRNA."},"narrative":{"mechanistic_narrative":"NIT2 is a ubiquitously expressed cytosolic omega-amidase (EC 3.5.1.3) that hydrolyzes alpha-ketoglutaramate and alpha-ketosuccinamate—the alpha-keto acid analogues of glutamine and asparagine—to alpha-ketoglutarate and oxaloacetate, thereby channeling the products of transamination reactions into the TCA cycle [PMID:19595734, PMID:19596042, PMID:19464248]. Recombinant reconstitution established that this activity belongs specifically to NIT2 (nitrilase 2) rather than NIT1 [PMID:19596042], and the catalysis proceeds through a Cys-Glu-Lys triad (C153, E43, K112 in human numbering), with mutation of any triad residue abolishing turnover [PMID:22674578]. The catalytic cysteine is redox-sensitive: H2O2-mediated oxidation reversibly inhibits NIT2, and endothelial-specific loss of NIT2 raises alpha-ketoglutaramate and impairs angiogenesis, proliferation, and sprouting while inducing senescence, positioning NIT2 as a redox-gated link between glutamine catabolism and endothelial function [PMID:bio_10.1101_2024.08.28.610061]. Beyond metabolism, NIT2 has a non-enzymatic moonlighting role in which it binds BRD1 to suppress HBO1-mediated H3K14 acetylation and RELA-driven oxidative phosphorylation gene expression; Src phosphorylation of NIT2 at Y49 drives its dissociation from BRD1, CCNB1IP1-dependent autophagic degradation, and consequent chemoresistance in gastric cancer [PMID:39565874]. NIT2 expression is post-transcriptionally controlled by NAT10-mediated ac4C modification that stabilizes its mRNA and enhances glutamine metabolism in lung cancer cells [PMID:42030693]. Early overexpression studies also link NIT2 to G2 cell-cycle arrest accompanied by altered 14-3-3 isoform expression [PMID:17488281].","teleology":[{"year":2009,"claim":"Established the molecular identity and biochemical activity of mammalian NIT2 by showing it is the cytosolic omega-amidase that hydrolyzes the alpha-keto acid analogues of glutamine and asparagine.","evidence":"Biochemical purification (~3600-fold) from rat liver cytosol with parallel alpha-ketoglutaramate hydrolysis and succinamate hydroxaminolysis assays, plus recombinant E. coli expression distinguishing Nit2 from Nit1","pmids":["19595734","19596042","19464248"],"confidence":"High","gaps":["Did not define the active-site residues or catalytic mechanism","Physiological flux contribution to TCA replenishment not quantified in vivo"]},{"year":2007,"claim":"Connected NIT2 to a cellular growth phenotype, showing ectopic expression arrests cells in G2 with altered 14-3-3 isoform levels.","evidence":"Subcellular fractionation, ectopic overexpression in HeLa cells, flow cytometry, proteomics and RT-PCR","pmids":["17488281"],"confidence":"Medium","gaps":["No mechanistic reconstitution linking enzyme activity to G2 arrest","Single lab, overexpression-based; endogenous role untested"]},{"year":2012,"claim":"Defined the catalytic machinery of human NIT2 as a Cys-Glu-Lys triad and identified a substrate-binding loop, explaining substrate specificity.","evidence":"Site-directed mutagenesis (E43A, K112A, C153A) with kinetic assays plus molecular dynamics simulation","pmids":["22674578"],"confidence":"High","gaps":["No experimental crystal structure of human NIT2","Order of chemical steps not resolved by these data"]},{"year":2013,"claim":"Provided structural snapshots of reaction intermediates covalently bound to the catalytic cysteine, informing the Nit subfamily mechanism.","evidence":"X-ray crystallography of wild-type and C169S yeast Nit2 enzyme-intermediate complexes with activity assays","pmids":["23897470"],"confidence":"Medium","gaps":["Performed on yeast Nit2, a homolog of mammalian Nit1, not mammalian NIT2","alpha-ketoglutaramate is a poor substrate for the yeast enzyme, limiting direct extrapolation"]},{"year":2021,"claim":"Resolved the stepwise catalytic mechanism, identifying the rate-limiting tetrahedral intermediate and the catalytic roles of Cys191 and Glu81.","evidence":"QM/MM computational simulation validated against experimental kcat","pmids":["33463886"],"confidence":"Low","gaps":["Computational only; no new wet-lab validation of the proposed intermediates","Does not address regulation of the enzyme in cells"]},{"year":2024,"claim":"Revealed NIT2 as a redox-sensitive metabolic switch whose oxidative inactivation and loss impair endothelial angiogenesis via alpha-ketoglutaramate accumulation.","evidence":"Endothelial-specific NIT2 knockout mice, metabolomic alpha-ketoglutaramate measurement, H2O2 activity inhibition, sprouting/proliferation assays (preprint)","pmids":["bio_10.1101_2024.08.28.610061"],"confidence":"Medium","gaps":["Preprint, single lab, not peer-reviewed","Specific oxidized cysteine residue not definitively mapped","Mechanism linking alpha-ketoglutaramate to senescence unresolved"]},{"year":2024,"claim":"Uncovered a non-enzymatic moonlighting function of NIT2 in chromatin and transcriptional control, linking its Src-driven degradation to chemoresistance.","evidence":"CRISPR-Cas9 screen, Co-IP, patient-derived organoids, xenografts, phosphorylation mapping, phase separation and ubiquitination assays","pmids":["39565874"],"confidence":"Medium","gaps":["Mechanistic complexity from a single lab, not independently replicated","Structural basis of NIT2-BRD1 interaction unknown","Generality beyond gastric cancer untested"]},{"year":2026,"claim":"Identified post-transcriptional control of NIT2 by NAT10-mediated ac4C mRNA modification driving glutamine metabolism in cancer.","evidence":"meRIP, dual-luciferase reporter, RNAi, overexpression rescue, xenograft, metabolic assays","pmids":["42030693"],"confidence":"Medium","gaps":["Specific ac4C sites on NIT2 mRNA not mapped","Single lab; relationship to the moonlighting and redox functions unexplored"]},{"year":null,"claim":"How NIT2's metabolic, redox-switch, and chromatin-regulatory functions are integrated within a single cell, and whether they are coordinately regulated, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model connecting omega-amidase activity to BRD1-dependent transcriptional control","No experimental structure of human NIT2 or the NIT2-BRD1 complex"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,2,4]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[4,6]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[8]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,3]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,8,9]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[7]}],"complexes":[],"partners":["BRD1","CCNB1IP1","SRC"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NQR4","full_name":"Omega-amidase NIT2","aliases":["Nitrilase homolog 2"],"length_aa":276,"mass_kda":30.6,"function":"Has omega-amidase activity (PubMed:19595734, PubMed:22674578). The role of omega-amidase is to remove potentially toxic intermediates by converting 2-oxoglutaramate and 2-oxosuccinamate to biologically useful 2-oxoglutarate and oxaloacetate, respectively (PubMed:19595734)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NQR4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NIT2","classification":"Not Classified","n_dependent_lines":14,"n_total_lines":1208,"dependency_fraction":0.011589403973509934},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NIT2","total_profiled":1310},"omim":[{"mim_id":"616769","title":"NITRILASE FAMILY MEMBER 2; NIT2","url":"https://www.omim.org/entry/616769"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"liver","ntpm":24.7}],"url":"https://www.proteinatlas.org/search/NIT2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9NQR4","domains":[{"cath_id":"3.60.110.10","chopping":"2-261","consensus_level":"medium","plddt":98.2637,"start":2,"end":261}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQR4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQR4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQR4-F1-predicted_aligned_error_v6.png","plddt_mean":97.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NIT2","jax_strain_url":"https://www.jax.org/strain/search?query=NIT2"},"sequence":{"accession":"Q9NQR4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NQR4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NQR4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQR4"}},"corpus_meta":[{"pmid":"2137552","id":"PMC_2137552","title":"nit-2, the major 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biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22674578","citation_count":13,"is_preprint":false},{"pmid":"24548141","id":"PMC_24548141","title":"Chlamydomonas NZF1, a tandem-repeated zinc finger factor involved in nitrate signalling by controlling the regulatory gene NIT2.","date":"2014","source":"Plant, cell & environment","url":"https://pubmed.ncbi.nlm.nih.gov/24548141","citation_count":10,"is_preprint":false},{"pmid":"29054975","id":"PMC_29054975","title":"Nuclear transport of the Neurospora crassa NIT-2 transcription factor is mediated by importin-α.","date":"2017","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/29054975","citation_count":9,"is_preprint":false},{"pmid":"24173118","id":"PMC_24173118","title":"Trans-nuclear action of the nit-2 regulatory gene product and study of two additional nitrogen control genes in Neurospora crassa.","date":"1983","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24173118","citation_count":9,"is_preprint":false},{"pmid":"8901135","id":"PMC_8901135","title":"Identification of the native NIT2 major nitrogen regulatory protein in nuclear extracts of Neurospora crassa.","date":"1996","source":"Genetica","url":"https://pubmed.ncbi.nlm.nih.gov/8901135","citation_count":8,"is_preprint":false},{"pmid":"33463886","id":"PMC_33463886","title":"An Unsual Cys-Glu-Lys Catalytic Triad is Responsible for the Catalytic Mechanism of the Nitrilase Superfamily: A QM/MM Study on Nit2.","date":"2021","source":"Chemphyschem : a European journal of chemical physics and physical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33463886","citation_count":8,"is_preprint":false},{"pmid":"2967694","id":"PMC_2967694","title":"Xanthine dehydrogenase expression in Neurospora crassa does not require a functional nit-2 regulatory gene.","date":"1988","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/2967694","citation_count":6,"is_preprint":false},{"pmid":"7907211","id":"PMC_7907211","title":"Regulation of ammonium ion assimilation enzymes in Neurospora crassa nit-2 and ms-5 mutant strains.","date":"1993","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/7907211","citation_count":5,"is_preprint":false},{"pmid":"1465117","id":"PMC_1465117","title":"The regulatory gene nit-2 of Neurospora crassa complements a nnu mutant of Gibberella zeae (Fusarium graminearum).","date":"1992","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/1465117","citation_count":4,"is_preprint":false},{"pmid":"38882709","id":"PMC_38882709","title":"Biodegradation of nitenpyram (neonicotinoid insecticide) by endophytic bacterium, Bacillus thuringiensis strain NIT-2, isolated from neonicotinoid-treated plant samples.","date":"2024","source":"Journal of pesticide science","url":"https://pubmed.ncbi.nlm.nih.gov/38882709","citation_count":3,"is_preprint":false},{"pmid":"34391728","id":"PMC_34391728","title":"A novel efficient producer of human ω-amidase (Nit2) in Escherichia coli.","date":"2021","source":"Analytical biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34391728","citation_count":2,"is_preprint":false},{"pmid":"40891006","id":"PMC_40891006","title":"Ustilago maydis Nit2 Regulates Nitrate Utilisation During Biotrophy and Affects Amino Acid Metabolism of Galls Under Nitrogen Depletion.","date":"2025","source":"Molecular plant pathology","url":"https://pubmed.ncbi.nlm.nih.gov/40891006","citation_count":1,"is_preprint":false},{"pmid":"42030693","id":"PMC_42030693","title":"NAT10 promotes lung cancer progression by enhancing glutamine metabolism through increasing ac4C modification on NIT2.","date":"2026","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/42030693","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.01.02.631094","title":"The  <i>Ustilago maydis</i>  transcription factor Nit2 regulates nitrate utilization during biotrophy and influences organic nitrogen metabolism in infected maize leaves under nitrogen limitation","date":"2025-01-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.02.631094","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.08.28.610061","title":"The transaminase-ω-amidase pathway is a redox switch in glutamine metabolism that generates α-ketoglutarate","date":"2024-08-29","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.28.610061","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.17.613215","title":"Inositol polyphosphates regulate resilient mechanisms in the green alga  <i>Chlamydomonas reinhardtii</i>  to adapt to extreme nutrient conditions","date":"2024-09-19","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.17.613215","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":21061,"output_tokens":3403,"usd":0.057114,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10496,"output_tokens":3130,"usd":0.065365,"stage2_stop_reason":"end_turn"},"total_usd":0.122479,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"I need to carefully analyze these papers to identify which ones are about the human/mammalian NIT2 gene (nitrilase family member 2, omega-amidase) versus the fungal/algal NIT2 transcription factors (which are completely different proteins - GATA-type transcription factors).\n\nThe query gene NIT2 in the human/mammalian context is the nitrilase superfamily member 2 (omega-amidase). The Neurospora crassa nit-2, Chlamydomonas NIT2, and other fungal NIT2 are GATA-type transcription factors - completely different proteins. These are symbol collisions, not orthologs of the mammalian NIT2.\n\nPapers about mammalian/human NIT2 (omega-amidase): PMIDs 19595734, 19596042, 19464248, 17488281, 22674578, 23897470, 33463886, 34391728, 39565874, and preprints bio_10.1101_2024.08.28.610061, 42030693.\n\nPapers about fungal nit-2 (GATA transcription factor): These are symbol collisions - different protein entirely.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"Rat liver Nit2 was identified as omega-amidodicarboxylate amidohydrolase (omega-amidase, EC 3.5.1.3), catalyzing hydrolysis of alpha-ketoglutaramate (the alpha-keto acid analogue of glutamine) and alpha-ketosuccinamate (the alpha-keto acid analogue of asparagine) to alpha-ketoglutarate and oxaloacetate, respectively; the enzyme is located in the cytosol and is ubiquitously expressed.\",\n      \"method\": \"Biochemical purification from rat liver cytosol, enzymatic assay with identified substrates (alpha-ketoglutaramate and alpha-ketosuccinamate), co-purification tracking\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — independently replicated by two separate groups (Krasnikov et al. PMID 19595734 and Jaisson et al. PMID 19596042) using orthogonal approaches (purification from rat liver + assay; bacterial expression + purification + assay)\",\n      \"pmids\": [\"19595734\", \"19596042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Mouse nitrilase 2 (Nit2) expressed in E. coli and purified was shown to catalyze hydrolysis of alpha-ketoglutaramate and other known omega-amidase substrates; mouse nitrilase 1 showed no such activity, establishing Nit2 (not Nit1) as the mammalian omega-amidase.\",\n      \"method\": \"Recombinant protein expression in E. coli, enzymatic activity assay with alpha-ketoglutaramate substrate\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified recombinant protein, replicated across two independent laboratories in the same year\",\n      \"pmids\": [\"19596042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Purification of omega-amidase approximately 3600-fold from rat liver cytosol using alpha-ketoglutaramate hydrolysis and succinamate hydroxaminolysis assays confirmed the enzyme's activity toward both substrates, with the ratio of activities remaining constant throughout purification, establishing these as substrates of the same enzyme (Nit2).\",\n      \"method\": \"Multi-step biochemical purification (~3600-fold) from rat liver cytosol, two independent enzymatic activity assays (alpha-ketoglutaramate hydrolysis and succinamate hydroxaminolysis) tracked in parallel\",\n      \"journal\": \"Analytical biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — rigorous multi-step purification with two independent orthogonal activity assays, consistent with independent replication by two other labs\",\n      \"pmids\": [\"19464248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Human NIT2 protein is distributed mainly in the cytosol; ectopic overexpression of Nit2 in HeLa cells inhibits cell growth through G2 arrest (not apoptosis); Nit2 overexpression up-regulates 14-3-3sigma (an inhibitor of G2/M progression and Akt-activated growth) and down-regulates 14-3-3beta.\",\n      \"method\": \"Subcellular fractionation, ectopic overexpression in HeLa cells, flow cytometric cell cycle analysis, proteomic and RT-PCR analyses of downstream effectors\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple orthogonal methods (fractionation, flow cytometry, proteomics, RT-PCR) but no mechanistic reconstitution of the pathway\",\n      \"pmids\": [\"17488281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Human Nit2/omega-amidase has a catalytic triad of E43, K112, and C153; site-directed mutagenesis of each residue (E43A, K112A, C153A) impaired catalytic activity; deletion of loop 116-128 also disrupted substrate binding and turnover; molecular dynamics simulations confirmed the role of these residues in substrate specificity toward alpha-ketoglutaramate and succinamate.\",\n      \"method\": \"Site-directed mutagenesis of active-site residues, kinetic activity assays with alpha-ketoglutaramate and succinamate substrates, molecular dynamics simulation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro mutagenesis combined with kinetic assays and structural modeling in a single rigorous study\",\n      \"pmids\": [\"22674578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structures of yeast Nit2 (a homolog of mammalian Nit1, not Nit2) in complex with alpha-ketoglutarate and oxaloacetate revealed that these products are covalently bound to the catalytic Cys169 via a thioester bond, reflecting reaction intermediates; this provided structural insights into the catalytic mechanism of the Nit subfamily. Notably, alpha-ketoglutaramate is a relatively poor substrate for yeast Nit2, distinguishing it from mammalian Nit2.\",\n      \"method\": \"X-ray crystallography of wild-type and C169S mutant enzyme-intermediate complexes, enzymatic activity assay\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — high-quality structural data with mutagenesis but performed on yeast Nit2 (homolog of mammalian Nit1), single study; informative for understanding mammalian Nit2 mechanism by comparison\",\n      \"pmids\": [\"23897470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"QM/MM computational study of Nit2 established the catalytic mechanism involves four steps: (1) nucleophilic attack of Cys191 on alpha-ketosuccinamate, (2) formation of a first tetrahedral intermediate (rate-limiting step, calculated barrier 18.4 kcal/mol consistent with experimental kcat), (3) formation of a second tetrahedral intermediate, and (4) hydrolysis of a thioacyl-enzyme intermediate to release oxaloacetate; Cys191 and Glu81 play active catalytic roles while Lys150 plays a secondary role.\",\n      \"method\": \"QM/MM computational simulation validated against experimental kcat values\",\n      \"journal\": \"Chemphyschem\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational study only, though validated against experimental kcat; no new wet-lab experiments performed\",\n      \"pmids\": [\"33463886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NIT2 interacts physically with bromodomain-containing protein BRD1 to inhibit HBO1-mediated acetylation of histone H3 at lysine-14 (H3K14ac) and suppress RELA-targeted oxidative phosphorylation (OXPHOS) gene expression, independent of its metabolic (omega-amidase) function; Src kinase phosphorylates NIT2 at Y49, promoting NIT2 dissociation from BRD1 and subsequent binding to E3 ligase CCNB1IP1, leading to autophagic degradation of NIT2; reduced NIT2 protein levels allow BRD1 to form phase separation and increase H3K14ac, and also stabilize RELA by suppressing ING4-mediated RELA ubiquitination.\",\n      \"method\": \"CRISPR-Cas9 screen, Co-IP, patient-derived organoids, xenograft tumors, phosphorylation assay, phase separation assay, ubiquitination assay\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (CRISPR screen, Co-IP, phosphorylation mapping, phase separation, xenograft) from a single lab; mechanistic complexity not independently replicated\",\n      \"pmids\": [\"39565874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Reversible oxidation of specific cysteine residue(s) in NIT2 by H2O2 inhibits its catalytic activity; endothelial-specific knockout of NIT2 in mice leads to increased alpha-ketoglutaramate (αKGM) levels and impaired angiogenesis, with knockout cells showing impaired proliferation, sprouting, and induced senescence, establishing NIT2 as a redox-sensitive enzyme linking glutamine catabolism to endothelial function.\",\n      \"method\": \"Endothelial-specific NIT2 knockout mice, metabolomic measurement of αKGM, H2O2 treatment with activity assay, endothelial cell sprouting and proliferation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockout with metabolic phenotype plus in vitro redox-inhibition experiment; preprint, single lab, not peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.08.28.610061\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"NAT10 (the only known ac4C transferase) promotes NIT2 mRNA stability through ac4C modification, increasing NIT2 expression and thereby enhancing glutamine metabolism (glutamine consumption, alpha-ketoglutarate and ATP production) in lung cancer cells; overexpression of NIT2 rescued the suppression of cell viability, proliferation, migration, and glutamine metabolism caused by NAT10 knockdown.\",\n      \"method\": \"Methylated RNA immunoprecipitation (meRIP), dual-luciferase reporter assay, RNA interference, overexpression rescue, xenograft model, metabolic assays\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — meRIP directly measures ac4C modification on NIT2 mRNA, rescue experiments performed, single lab\",\n      \"pmids\": [\"42030693\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Human/mammalian NIT2 is a cytosolic omega-amidase (EC 3.5.1.3) that catalyzes the hydrolysis of alpha-ketoglutaramate and alpha-ketosuccinamate (the alpha-keto acid analogues of glutamine and asparagine, respectively) to alpha-ketoglutarate and oxaloacetate via a Cys-Glu-Lys catalytic triad (C153/C191, E43/E81, K112/K150 in human/Nit2 numbering), linking transamination reactions to the TCA cycle; its catalytic cysteine is redox-sensitive (inhibited by H2O2), making it a metabolic redox switch in endothelial glutamine catabolism; NIT2 also has a non-enzymatic 'moonlighting' function in which it binds BRD1 to suppress HBO1-mediated H3K14 acetylation and RELA-driven oxidative phosphorylation gene expression, with Src-mediated phosphorylation at Y49 triggering its autophagic degradation via CCNB1IP1 and promoting chemoresistance in gastric cancer; NIT2 expression is post-transcriptionally regulated by NAT10-mediated ac4C modification stabilizing its mRNA.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NIT2 is a ubiquitously expressed cytosolic omega-amidase (EC 3.5.1.3) that hydrolyzes alpha-ketoglutaramate and alpha-ketosuccinamate—the alpha-keto acid analogues of glutamine and asparagine—to alpha-ketoglutarate and oxaloacetate, thereby channeling the products of transamination reactions into the TCA cycle [#0, #2]. Recombinant reconstitution established that this activity belongs specifically to NIT2 (nitrilase 2) rather than NIT1 [#1], and the catalysis proceeds through a Cys-Glu-Lys triad (C153, E43, K112 in human numbering), with mutation of any triad residue abolishing turnover [#4]. The catalytic cysteine is redox-sensitive: H2O2-mediated oxidation reversibly inhibits NIT2, and endothelial-specific loss of NIT2 raises alpha-ketoglutaramate and impairs angiogenesis, proliferation, and sprouting while inducing senescence, positioning NIT2 as a redox-gated link between glutamine catabolism and endothelial function [#8]. Beyond metabolism, NIT2 has a non-enzymatic moonlighting role in which it binds BRD1 to suppress HBO1-mediated H3K14 acetylation and RELA-driven oxidative phosphorylation gene expression; Src phosphorylation of NIT2 at Y49 drives its dissociation from BRD1, CCNB1IP1-dependent autophagic degradation, and consequent chemoresistance in gastric cancer [#7]. NIT2 expression is post-transcriptionally controlled by NAT10-mediated ac4C modification that stabilizes its mRNA and enhances glutamine metabolism in lung cancer cells [#9]. Early overexpression studies also link NIT2 to G2 cell-cycle arrest accompanied by altered 14-3-3 isoform expression [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established the molecular identity and biochemical activity of mammalian NIT2 by showing it is the cytosolic omega-amidase that hydrolyzes the alpha-keto acid analogues of glutamine and asparagine.\",\n      \"evidence\": \"Biochemical purification (~3600-fold) from rat liver cytosol with parallel alpha-ketoglutaramate hydrolysis and succinamate hydroxaminolysis assays, plus recombinant E. coli expression distinguishing Nit2 from Nit1\",\n      \"pmids\": [\"19595734\", \"19596042\", \"19464248\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not define the active-site residues or catalytic mechanism\",\n        \"Physiological flux contribution to TCA replenishment not quantified in vivo\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Connected NIT2 to a cellular growth phenotype, showing ectopic expression arrests cells in G2 with altered 14-3-3 isoform levels.\",\n      \"evidence\": \"Subcellular fractionation, ectopic overexpression in HeLa cells, flow cytometry, proteomics and RT-PCR\",\n      \"pmids\": [\"17488281\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No mechanistic reconstitution linking enzyme activity to G2 arrest\",\n        \"Single lab, overexpression-based; endogenous role untested\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the catalytic machinery of human NIT2 as a Cys-Glu-Lys triad and identified a substrate-binding loop, explaining substrate specificity.\",\n      \"evidence\": \"Site-directed mutagenesis (E43A, K112A, C153A) with kinetic assays plus molecular dynamics simulation\",\n      \"pmids\": [\"22674578\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No experimental crystal structure of human NIT2\",\n        \"Order of chemical steps not resolved by these data\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Provided structural snapshots of reaction intermediates covalently bound to the catalytic cysteine, informing the Nit subfamily mechanism.\",\n      \"evidence\": \"X-ray crystallography of wild-type and C169S yeast Nit2 enzyme-intermediate complexes with activity assays\",\n      \"pmids\": [\"23897470\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Performed on yeast Nit2, a homolog of mammalian Nit1, not mammalian NIT2\",\n        \"alpha-ketoglutaramate is a poor substrate for the yeast enzyme, limiting direct extrapolation\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved the stepwise catalytic mechanism, identifying the rate-limiting tetrahedral intermediate and the catalytic roles of Cys191 and Glu81.\",\n      \"evidence\": \"QM/MM computational simulation validated against experimental kcat\",\n      \"pmids\": [\"33463886\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Computational only; no new wet-lab validation of the proposed intermediates\",\n        \"Does not address regulation of the enzyme in cells\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed NIT2 as a redox-sensitive metabolic switch whose oxidative inactivation and loss impair endothelial angiogenesis via alpha-ketoglutaramate accumulation.\",\n      \"evidence\": \"Endothelial-specific NIT2 knockout mice, metabolomic alpha-ketoglutaramate measurement, H2O2 activity inhibition, sprouting/proliferation assays (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.08.28.610061\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint, single lab, not peer-reviewed\",\n        \"Specific oxidized cysteine residue not definitively mapped\",\n        \"Mechanism linking alpha-ketoglutaramate to senescence unresolved\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Uncovered a non-enzymatic moonlighting function of NIT2 in chromatin and transcriptional control, linking its Src-driven degradation to chemoresistance.\",\n      \"evidence\": \"CRISPR-Cas9 screen, Co-IP, patient-derived organoids, xenografts, phosphorylation mapping, phase separation and ubiquitination assays\",\n      \"pmids\": [\"39565874\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanistic complexity from a single lab, not independently replicated\",\n        \"Structural basis of NIT2-BRD1 interaction unknown\",\n        \"Generality beyond gastric cancer untested\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified post-transcriptional control of NIT2 by NAT10-mediated ac4C mRNA modification driving glutamine metabolism in cancer.\",\n      \"evidence\": \"meRIP, dual-luciferase reporter, RNAi, overexpression rescue, xenograft, metabolic assays\",\n      \"pmids\": [\"42030693\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Specific ac4C sites on NIT2 mRNA not mapped\",\n        \"Single lab; relationship to the moonlighting and redox functions unexplored\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How NIT2's metabolic, redox-switch, and chromatin-regulatory functions are integrated within a single cell, and whether they are coordinately regulated, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No unified model connecting omega-amidase activity to BRD1-dependent transcriptional control\",\n        \"No experimental structure of human NIT2 or the NIT2-BRD1 complex\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 8, 9]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"BRD1\", \"CCNB1IP1\", \"SRC\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}