AKR1A1

AKR1A1 is an NADPH-dependent aldo-keto reductase that operates at the intersection of detoxification metabolism, ascorbate biosynthesis, and nitric oxide–based redox signaling (PMID:31649033, PMID:28060768). As a classical oxidoreductase it oxidizes polycyclic aromatic hydrocarbon trans-dihydrodiols to reactive o-quinones with strict regio- and stereoselectivity (PMID:11535067, PMID:11306097) and catalyzes the conversion of D-glucuronate to L-gulonate, an essential step in ascorbic acid synthesis; its genetic ablation in mice causes ascorbate insufficiency, abnormal bone development, and osteoporosis that is reversed by ascorbate supplementation (PMID:28060768). Beyond these reductase roles, AKR1A1 functions as a low-molecular-weight S-nitroso denitrosylase (SCoR2), reducing both S-nitroso-CoA and S-nitroso-glutathione through distinct substrate-binding residues—Lys-127 for SNO-CoA and Arg-312 for GSNO—thereby controlling cellular protein S-nitrosylation (PMID:31649033). In classically activated macrophages, induction of AKR1A1 requires both NO• and LPS/IFNγ, and its SNO-CoA reductase activity limits inhibitory S-nitrosylation of the pyruvate dehydrogenase complex lipoyl cofactor, forming a negative regulatory loop that restrains NO•-driven TCA cycle remodeling and shapes immunometabolite and cytokine output (PMID:42048774, PMID:41509239). Loss-of-function variants link AKR1A1 to human disease: a silent c.753G>A variant induces exon 8 skipping, abolishing enzymatic activity and causing glucuronate accumulation, in an association with schizophrenia (PMID:34938315). AKR1A1 additionally contributes to cellular handling of reactive aldehydes and oxidative stress (PMID:23643085) and is transcriptionally driven by an E47/β-catenin axis downstream of RORα in gastric cancer, where it promotes glycolytic and lipogenic reprogramming (PMID:40096932).

1. 1999 Medium

   Establishing the genomic architecture of human AKR1A1 provided the foundation for interpreting later coding and splicing variants.

   Evidence Genomic sequencing and FISH localization to chromosome 1p33→p32

   PMID:10393438

   Open questions at the time

   • No functional or enzymatic characterization
   • Does not address tissue expression or regulation
2. 2001 High

   Defining AKR1A1 as an oxidative metabolizer of PAH trans-dihydrodiols answered whether the enzyme contributes to carcinogen activation and showed it does so with marked selectivity.

   Evidence In vitro kinetics with purified recombinant enzyme, CD, and LC/MS product trapping

   PMID:11306097 PMID:11535067

   Open questions at the time

   • In vivo relevance to carcinogenesis not tested
   • Cellular regulation of this activity unknown
3. 2007 Medium

   Site-specific immobilization studies established that active-site accessibility, not the C-terminus, governs catalytic competence.

   Evidence Expressed protein ligation and biotin-streptavidin immobilization with kinetic comparison

   PMID:17508367

   Open questions at the time

   • Technical/biophysical focus rather than physiological
   • No structural model of the active site provided
4. 2011 Medium

   Testing AKR1A1's role in GHB metabolism in astrocytoma resolved that it is not a major contributor to endogenous GHB biosynthesis, narrowing its physiological substrate scope.

   Evidence siRNA knockdown with enzymatic activity assays and GC/MS GHB measurement in 1321N1 cells

   PMID:21276435

   Open questions at the time

   • Negative finding in a single cell line
   • Did not identify the dominant SSA reductase
5. 2013 Low

   Knockdown phenotypes implicated AKR1A1 in resistance to oxidative and aldehyde stress, extending its role to cytoprotection.

   Evidence siRNA knockdown with viability and ROS assays in 1321N1 astrocytoma cells

   PMID:23643085

   Open questions at the time

   • Single siRNA approach without enzymatic confirmation of 4-HNE turnover
   • No rescue experiment
   • Single cell line
6. 2014 Medium

   HepG2 knockdown clarified that AKR1A1 oxidizes GHB to succinic semialdehyde only at high concentrations, defining a catabolic but not biosynthetic role.

   Evidence siRNA knockdown with NADP-dependent activity assays and GC/MS GHB quantitation in HepG2 cells

   PMID:25256836

   Open questions at the time

   • Physiological GHB concentrations may not engage this activity
   • Single cell line
7. 2017 High

   Knockout mice established AKR1A1 as the in vivo D-glucuronate-to-L-gulonate enzyme essential for ascorbate synthesis, linking enzyme loss to skeletal pathology.

   Evidence Akr1a1 knockout mice, serum metabolite measurement, micro-CT, and ascorbate rescue

   PMID:28060768

   Open questions at the time

   • Human ascorbate dependence differs from mouse
   • Other AKRs may compensate in some tissues
8. 2019 High

   De novo purification and KO validation identified AKR1A1 as a primary GSNO reductase with substrate-binding residues distinct from those for SNO-CoA, establishing it as a multi-LMW-SNO denitrosylase with cross-talk to GSNOR.

   Evidence Tissue purification of NADPH-coupled GSNOR activity, AKR1A1 KO mice, and Arg-312/Lys-127 mutagenesis with modeling

   PMID:31649033

   Open questions at the time

   • Downstream S-nitrosylated protein targets not enumerated here
   • Physiological consequences of denitrosylase activity not yet mapped
9. 2021 Medium

   A schizophrenia-associated silent variant was shown to cause exon 8 skipping and complete loss of enzyme activity, providing a mechanistic genotype-to-function link and a disease association.

   Evidence Minigene splicing assay, recombinant truncated protein activity, and patient blood mRNA/AKR activity

   PMID:34938315

   Open questions at the time

   • Small clinical sample for the schizophrenia association
   • Causal mechanism connecting glucuronate accumulation to phenotype unestablished
10. 2025 Medium

    Cancer and macrophage studies connected AKR1A1 expression to metabolic reprogramming, placing it under an E47/β-catenin/RORα transcriptional axis and within lactylation-modulated signaling.

    Evidence Co-IP, ChIP, luciferase, Seahorse in gastric cancer cells; Co-IP lactylation and CellChat analysis in RAW264.7 macrophages

    PMID:40096932 PMID:41246341

    Open questions at the time

    • Lactylation pathway placement is largely computational (CellChat)
    • Whether reprogramming requires enzymatic vs. expression-level changes is unresolved
11. 2025 Medium

    Cardiac SCoR2/AKR1A1 deletion was shown to coordinately reprogram ketone, glycolytic, pentose phosphate, and polyol metabolism via S-nitrosylation, conferring myocardial-infarction protection.

    Evidence Akr1a1 KO mice in a myocardial infarction model with metabolomics and S-nitrosylation proteomics (preprint)

    PMID:bio_10.1101_2025.03.12.642752

    Open questions at the time

    • Preprint, not peer-reviewed
    • Specific S-nitrosylated effectors driving cardioprotection not pinpointed
12. 2026 High

    Macrophage studies defined AKR1A1 as a negative regulator of NO•-driven metabolic remodeling by limiting inhibitory S-nitrosylation of the PDC lipoyl cofactor.

    Evidence Multi-omics, Akr1a1 KO macrophages, metabolite and cytokine assays

    PMID:41509239 PMID:42048774

    Open questions at the time

    • Direct demonstration that PDC lipoyl SNO is the proximate AKR1A1 substrate in cells is inferential
    • Generalization beyond classically activated macrophages untested

• How AKR1A1's distinct activities—carcinogen oxidation, ascorbate synthesis, and SNO denitrosylation—are coordinately regulated and prioritized across tissues remains unresolved.
• No structural basis distinguishing reductase vs. denitrosylase substrate selection in vivo
• The full set of S-nitrosylated protein targets controlled by AKR1A1 is uncatalogued
• Tissue-specific determinants of which activity dominates are unknown