Affinage

CTPS2

CTP synthase 2 · UniProt Q9NRF8

Length
586 aa
Mass
65.7 kDa
Annotated
2026-04-28
35 papers in source corpus 12 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CTPS2 is a CTP synthase that catalyzes the ATP- and glutamine-dependent conversion of UTP to CTP, functioning as the primary housekeeping isoform for de novo CTP biosynthesis in non-lymphoid tissues while serving as an essential backup to CTPS1 in proliferating lymphocytes (PMID:16179339, PMID:34583994, PMID:37348953, PMID:38438357). CTPS2 assembles into homotetramers that further polymerize into filamentous structures (cytoophidia), and cryo-EM studies demonstrate that filament assembly enables ultrasensitive cooperative switching between active and inactive conformations in response to substrate and product levels, with CTP feedback inhibition acting through two binding sites that sterically clash with substrates (PMID:31873303, PMID:34583994). Enzymatic activity is negatively regulated by casein kinase 1-mediated phosphorylation at Ser568, which preferentially suppresses the glutaminase partial reaction, and by direct heterocomplex formation with CTPS1, which reduces activity and increases CTP sensitivity (PMID:20739275, PMID:40957650). Conditional Ctps2 deletion in mice is viable but impairs T cell proliferative responses following TCR stimulation, and combined CTPS1/CTPS2 loss causes severe DNA damage and proliferation arrest in EBV-transformed B cells, underscoring the partially redundant but individually required roles of both isoforms in lymphocyte biology (PMID:38438357, PMID:34281398).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2005 High

    Establishing that CTPS2 encodes a functional CTP synthase: complementation of yeast lacking all CTP synthase activity proved that CTPS2 is sufficient for de novo CTP production in vivo, resolving its identity as a bona fide CTP synthase rather than a pseudogene or non-catalytic paralog.

    Evidence Yeast ura7Δura8Δ complementation with human CTPS2, immunoblot, in vivo CTP measurement, and enzymatic activity assay

    PMID:16179339

    Open questions at the time
    • No comparison with CTPS1 activity in same system
    • Mammalian in vivo function not yet addressed
  2. 2010 High

    Defining CTPS2 kinetic parameters and identifying inhibitory phosphorylation revealed how the enzyme is tuned to physiological nucleotide concentrations and post-translationally suppressed: casein kinase 1 phosphorylation at Ser568 inhibits CTPS2, preferentially affecting the glutaminase partial reaction, establishing a direct regulatory mechanism.

    Evidence Purified recombinant enzyme kinetics, metabolic 32P-labeling, phosphopeptide mapping, S568A mutagenesis, in vitro CK1 kinase assay

    PMID:20739275

    Open questions at the time
    • Physiological contexts triggering CK1-mediated phosphorylation unknown
    • No structural basis for how Ser568 phosphorylation affects glutaminase domain
  3. 2011 Medium

    Linking CTPS2 to chemosensitivity: CTPS2 knockdown in colorectal cancer cells conferred resistance to 5-FU, connecting pyrimidine synthesis flux through CTPS2 to fluoropyrimidine drug action.

    Evidence siRNA knockdown in colorectal cancer cell lines, cell cycle analysis, apoptosis assay, uridine rescue

    PMID:21378502

    Open questions at the time
    • Mechanism by which CTPS2 loss specifically confers 5-FU resistance not fully dissected
    • In vivo relevance in tumors not tested
  4. 2019 High

    Cryo-EM structures of CTPS2 filaments explained how polymerization achieves ultrasensitive regulation: filaments couple the conformational states of many subunits, enabling cooperative switching between active and inactive states far exceeding what the tetramer alone can achieve, and linking conformation to control of ammonia channeling.

    Evidence Cryo-EM structural determination of CTPS2 filaments in active and inactive states with biochemical cooperativity analysis

    PMID:31873303

    Open questions at the time
    • In vivo regulation of filament assembly/disassembly dynamics not characterized
    • How post-translational modifications affect filament conformation unknown
  5. 2020 Medium

    Discovery that CTPS2 filaments are organized along the cytokeratin network via KRT8 and SNAP29 linked spatial positioning of cytoophidia to metabolic regulation: SNAP29 knockdown disrupted filament assembly and relieved suppression of CTPS activity under glutamine deprivation.

    Evidence CTPS-APEX2 proximity labeling, SNAP29 knockdown, super-resolution imaging, enzymatic activity assays

    PMID:32184263

    Open questions at the time
    • Whether KRT8/SNAP29-dependent assembly is specific to CTPS2 versus CTPS1 filaments unclear
    • Direct binding between SNAP29 and CTPS2 not demonstrated with purified components
  6. 2021 High

    Structural basis for isoform-selective CTP feedback inhibition was resolved: CTPS2 is more sensitive to CTP inhibition than CTPS1, with a single amino acid difference responsible, explaining why CTPS1 is preferentially used during rapid lymphocyte proliferation while CTPS2 serves housekeeping roles.

    Evidence Cryo-EM structures of CTPS1 filaments with inhibitors, mutagenesis of selectivity-determining residue, biochemical inhibition assays comparing isoforms

    PMID:34583994

    Open questions at the time
    • Whether tissue-specific expression fully explains isoform division of labor not resolved
    • No structure of a CTPS1–CTPS2 heterocomplex
  7. 2021 Medium

    Functional redundancy between CTPS1 and CTPS2 was demonstrated in EBV-transformed B cells: double knockout caused more severe DNA damage and proliferation defects than single CTPS1 loss, with cytidine rescue confirming the phenotype is due to CTP depletion.

    Evidence CRISPR knockout of CTPS1 and/or CTPS2 in EBV-transformed lymphoblastoid cell lines, DNA damage assays, cytidine rescue

    PMID:34281398

    Open questions at the time
    • Whether CTPS2 upregulation by EBV is transcriptionally or post-transcriptionally driven not resolved
    • Relative CTP contribution of each isoform not quantified
  8. 2023 High

    Genetic hierarchy between isoforms was established: CTPS2 contributes modestly to proliferation when CTPS1 is present but becomes essential in CTPS1-null cells, confirming CTPS2 as a lower-activity backup enzyme.

    Evidence CTPS1 and/or CTPS2 gene knockout, complementation, in vitro enzymatic activity assays, cell proliferation assays

    PMID:37348953

    Open questions at the time
    • Whether CTPS2 can be upregulated to fully compensate for CTPS1 loss in any tissue not known
    • Structural basis for lower intrinsic activity of CTPS2 not identified
  9. 2024 High

    In vivo mouse genetics demonstrated that Ctps2 is individually required for T cell proliferation but dispensable for embryonic development, distinguishing it from the embryonic-lethal Ctps1 knockout and confirming a non-redundant role specifically in adaptive immune responses.

    Evidence Conditional and inducible Ctps1 and Ctps2 mouse knockouts, T cell proliferation assays following TCR stimulation

    PMID:38438357

    Open questions at the time
    • Whether CTPS2 is required in other rapidly proliferating cell types in vivo not tested
    • Mechanism by which TCR stimulation upregulates CTPS2 demand not resolved
  10. 2025 High

    Direct CTPS1–CTPS2 heterocomplex formation was established as a regulatory mechanism: CTPS2 physically interacts with CTPS1 independent of polymerization, decreasing CTPS1 activity and increasing CTP sensitivity, providing a mechanism for CTPS2 to act as a brake on CTP synthesis.

    Evidence Co-immunoprecipitation, polymerization-deficient H355A mutants, enzymatic activity and CTP feedback inhibition assays, co-localization imaging

    PMID:40957650

    Open questions at the time
    • Stoichiometry and structure of the heterocomplex not determined
    • Whether heterocomplex formation is regulated by cell state or signaling unknown
    • In vivo physiological relevance of heterocomplex not yet demonstrated in animal models

Open questions

Synthesis pass · forward-looking unresolved questions
  • Outstanding question: how do post-translational modifications (e.g., CK1 phosphorylation), filament assembly, heterocomplex formation with CTPS1, and cytokeratin-network localization integrate to regulate CTPS2 activity in different cell types and metabolic states in vivo?
  • No structural model of the CTPS1–CTPS2 heterotetramer
  • In vivo dynamics of filament assembly and disassembly are uncharacterized
  • Tissue-specific regulation of CTPS2 expression and post-translational modification remains undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016874 ligase activity 5 GO:0016740 transferase activity 3
Localization
GO:0005829 cytosol 2 GO:0005856 cytoskeleton 1
Pathway
R-HSA-1430728 Metabolism 6 R-HSA-168256 Immune System 2
Partners
CSNK1A1CTPS1KRT8SNAP29
Complex memberships
CTPS1-CTPS2 heterocomplexCTPS2 homotetramer

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2019 Cryo-EM structures reveal that human CTPS2 filaments dynamically switch between active and inactive conformational states in response to changes in substrate and product levels, with filament assembly linking the conformational state of many subunits to achieve highly cooperative (ultrasensitive) regulation that greatly exceeds the cooperativity limits of the CTPS2 tetramer alone. The structures also reveal a link between conformation and control of ammonia channeling between the enzyme's active sites. Cryo-EM structural determination of CTPS2 filaments in active and inactive states, combined with biochemical analysis of cooperativity Nature structural & molecular biology High 31873303
2010 Human CTPS2 is phosphorylated at Ser568 by casein kinase 1 both in vitro and in vivo, and this phosphorylation acts as a major inhibitory modification; the S568A mutation significantly increases CTPS2 activity, with a greater effect on glutamine-dependent than ammonia-dependent activity, suggesting phosphorylation influences the glutaminase domain. Ser571 was also identified as a phosphorylation site but did not significantly affect activity. Metabolic 32P-labeling, phosphoamino acid and phosphopeptide mapping, site-directed mutagenesis (S568A), in vitro kinase assay with casein kinase 1, kinetic analysis The Journal of biological chemistry High 20739275
2010 Kinetic analysis of purified human CTPS2 showed that both hCTPS1 and hCTPS2 are maximally active at physiological ATP, GTP, and glutamine concentrations, while the Km for substrate UTP and IC50 for product CTP are close to their physiological concentrations, indicating that intracellular UTP and CTP concentrations precisely regulate CTPS2 activity. CTPS2 forms oligomers as part of its regulatory mechanism. Kinetic analysis of purified recombinant enzymes The Journal of biological chemistry High 20739275
2005 Human CTPS2 is functionally expressed in yeast and complements the lethal phenotype of the ura7Δura8Δ double mutant lacking CTP synthase activity, demonstrating that CTPS2 encodes a functional CTP synthase enzyme capable of producing CTP in vivo. Yeast genetic complementation, immunoblot, in vivo CTP measurement, CTP synthase activity assay The Journal of biological chemistry High 16179339
2021 Cryo-EM structures of human CTPS1 filaments bound to small-molecule inhibitors reveal that CTP regulates both CTPS isoforms by binding in two sites that clash with substrates; CTPS1 is less sensitive to CTP feedback inhibition than CTPS2, consistent with its role in expanding CTP pools during lymphocyte proliferation. Demand for CTP in non-lymphoid tissues is met by the CTPS2 isoform. Cryo-EM structure determination of CTPS1 filaments, biochemical inhibition assays, site-directed mutagenesis identifying single amino acid responsible for isoform selectivity Proceedings of the National Academy of Sciences of the United States of America High 34583994
2023 CTPS1 has higher intrinsic enzymatic activity than CTPS2 and is more resistant to inhibition by 3-deaza-uridine. CTPS2 contributes modestly to cell proliferation when CTPS1 is expressed, but becomes essential in the absence of CTPS1, demonstrating that CTPS2 can substitute for CTPS1 as a CTP-producing enzyme but is less efficient. CTPS1 and/or CTPS2 inactivation by gene knockout, complementation experiments, in vitro enzymatic activity assays, cell proliferation assays Life science alliance High 37348953
2025 CTPS1 and CTPS2 directly interact with each other independently of polymerization or cytoophidia formation, forming heterocomplexes (likely heterotetramers). When CTPS2 is associated with CTPS1, CTPS1 enzymatic activity is decreased and becomes more sensitive to CTP product feedback inhibition. CTPS2-containing filaments are dependent on CTPS1 expression, and CTPS1 and CTPS2 co-localize in cytoophidia when co-expressed. Co-immunoprecipitation, co-localization imaging, CTPS1H355A and CTPS2H355A polymerization-deficient mutants, enzymatic activity assays, CTP feedback inhibition assays Life science alliance High 40957650
2021 EBV upregulates CTPS2 (and CTPS1) with distinct kinetics in newly infected B cells. Double CTPS1/2 knockout caused stronger DNA damage and proliferation defects than CTPS1 knockout alone in EBV-transformed lymphoblastoid cell lines, demonstrating that CTPS1 and CTPS2 have partially redundant roles in EBV-transformed B cells. Cytidine rescued the CTPS1/2 double-deficiency phenotypes. CRISPR knockout of CTPS1 and/or CTPS2, proliferation and DNA damage assays, cytidine rescue experiments mBio Medium 34281398
2024 Conditional deletion of Ctps2 (but not Ctps1) in mice is not embryonic lethal, whereas Ctps1 deletion is. Both CTPS1 and CTPS2 are required for T cell proliferation following TCR stimulation, demonstrated by the finding that loss of Ctps2 alone impairs T cell proliferative responses. Conditional and inducible mouse gene knockout of Ctps1 and/or Ctps2, T cell proliferation assays following TCR stimulation Nature communications High 38438357
2020 CTPS2 filaments assemble along the cytokeratin network in a keratin 8 (KRT8)-dependent manner, facilitated by SNAP29. SNAP29 knockdown interfered with filament assembly and relieved filament-induced suppression of CTPS enzymatic activity, linking cytokeratin network localization to regulation of CTPS metabolic activity under glutamine deprivation. CTPS-APEX2 proximity labeling in vivo, SNAP29 knockdown, super-resolution imaging, enzymatic activity assays Journal of cell science Medium 32184263
2023 CTPS2 mediates DNA damage response in chronic lymphocytic leukemia cells by interacting with BRCA1 protein; silencing CTPS2 elevated DNA damage and decreased DNA repair, and these effects were reversed by adding CTP or glutamine. Co-immunoprecipitation of CTPS2 and BRCA1, RNA-seq, siRNA knockdown, DNA damage assays, rescue experiments with CTP/glutamine Experimental hematology & oncology Low 36635772
2021 CTPS2 was identified as a potential interacting partner of the glutamine transporter SNAT6 in neurons; proximity ligation assays and co-expression analysis suggested a spatial association between SNAT6 and CTPS2 at the pre-synaptic terminal. Bioinformatics prediction, proximity ligation assay, co-localization analysis International journal of molecular sciences Low 33503881
2011 CTPS2 knockdown by siRNA in colorectal cancer cell lines increased resistance to 5-FU and its analogue FUDR, and significantly reduced S-phase accumulation and apoptosis following 5-FU treatment, demonstrating a role for CTPS2 in mediating 5-FU sensitivity through pyrimidine synthesis. siRNA knockdown, cell cycle analysis, apoptosis assay, uridine modulation Cancer biology & therapy Medium 21378502

Source papers

Stage 0 corpus · 35 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2014 CTP synthase 1 deficiency in humans reveals its central role in lymphocyte proliferation. Nature 177 24870241
2008 CTP synthetase and its role in phospholipid synthesis in the yeast Saccharomyces cerevisiae. Progress in lipid research 68 18439916
2019 Coupled structural transitions enable highly cooperative regulation of human CTPS2 filaments. Nature structural & molecular biology 59 31873303
2018 Characterization of filament-forming CTP synthases from Arabidopsis thaliana. The Plant journal : for cell and molecular biology 45 30030857
2022 Combined Inactivation of CTPS1 and ATR Is Synthetically Lethal to MYC-Overexpressing Cancer Cells. Cancer research 44 35022212
2010 Regulation of human cytidine triphosphate synthetase 2 by phosphorylation. The Journal of biological chemistry 33 20739275
2005 Expression of Human CTP synthetase in Saccharomyces cerevisiae reveals phosphorylation by protein kinase A. The Journal of biological chemistry 33 16179339
2021 Structural basis for isoform-specific inhibition of human CTPS1. Proceedings of the National Academy of Sciences of the United States of America 32 34583994
2004 The modulation of osteogenesis in vitro by calcium titanium phosphate coatings. Biomaterials 31 15109851
2021 Epstein-Barr Virus Induced Cytidine Metabolism Roles in Transformed B-Cell Growth and Survival. mBio 28 34281398
2019 Uridine/UMP metabolism and their function on the gut in segregated early weaned piglets. Food & function 27 31231750
2021 Extraction, Structural Characterization, and Anti-Hepatocellular Carcinoma Activity of Polysaccharides From Panax ginseng Meyer. Frontiers in oncology 25 34912721
2021 Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine-Glutamate Cycle. International journal of molecular sciences 21 33503881
2023 Differential roles of CTP synthetases CTPS1 and CTPS2 in cell proliferation. Life science alliance 19 37348953
2023 CTPS1 is a novel therapeutic target in multiple myeloma which synergizes with inhibition of CHEK1, ATR or WEE1. Leukemia 18 37898670
2021 Chloroplast quality control pathways are dependent on plastid DNA synthesis and nucleotides provided by cytidine triphosphate synthase two. The New phytologist 15 33993494
2020 SNAP29 mediates the assembly of histidine-induced CTP synthase filaments in proximity to the cytokeratin network. Journal of cell science 13 32184263
2011 Low cytosine triphosphate synthase 2 expression renders resistance to 5-fluorouracil in colorectal cancer. Cancer biology & therapy 13 21378502
2023 CTP Synthase 1 Is a Novel Therapeutic Target in Lymphoma. HemaSphere 11 37008165
2018 Inhibition of the Neuronal Calcium Sensor DREAM Modulates Presenilin-2 Endoproteolysis. Frontiers in molecular neuroscience 11 30559648
2022 A multiauxotrophic CHO cell line for the rapid isolation of producers of diverse or high levels of recombinant proteins. Biotechnology and bioengineering 9 35249214
2023 CTP synthase 2 predicts inferior survival and mediates DNA damage response via interacting with BRCA1 in chronic lymphocytic leukemia. Experimental hematology & oncology 8 36635772
2021 Cytosolic CTP Production Limits the Establishment of Photosynthesis in Arabidopsis. Frontiers in plant science 8 34917117
2024 Inactivation of cytidine triphosphate synthase 1 prevents fatal auto-immunity in mice. Nature communications 7 38438357
2023 Genome-wide association study reveals the candidate genes for reproduction traits in Yunong black pigs. Animal genetics 6 36650110
2022 Combined metabolomics and proteomics to reveal beneficial mechanisms of Dendrobium fimbriatum against gastric mucosal injury. Frontiers in pharmacology 6 36110550
2021 CTP Synthase 2 From Arabidopsis thaliana Is Required for Complete Embryo Development. Frontiers in plant science 6 33936137
2011 Comprehensive evaluation of the contribution of X chromosome genes to platinum sensitivity. Molecular cancer therapeutics 6 21252287
2022 Identification of a novel microdeletion causative of Nance-Horan syndrome. Molecular genetics & genomic medicine 5 35122698
2017 Identification of cytidine-5-triphosphate synthase1-selective inhibitory peptide from random peptide library displayed on T7 phage. Peptides 5 28676225
2004 Organization and annotation of the Xcat critical region: elimination of seven positional candidate genes. Genomics 4 15081118
2023 Stem cell factor modulates HIF-1α levels and diminishes 5-FU sensitivity in 5-FU resistant pancreatic cells by altering the anabolic glucose metabolism. Journal of biochemical and molecular toxicology 1 37718545
2018 The Challenge of Next Generation Sequencing in a Boy With Severe Mononucleosis and EBV-related Lymphoma. Journal of pediatric hematology/oncology 1 29176466
2026 Spliceosomal component SNRPE drives cell proliferation by regulating CTP synthase 1 mRNA splicing in ovarian cancer. Oncogene 0 41933137
2025 CTPS2 regulates CTP synthetase activity by interacting with CTPS1. Life science alliance 0 40957650