DHTKD1 is the E1 component (E1a; 2-oxoadipate dehydrogenase, OADH-E1) of the mitochondrial 2-oxoadipate dehydrogenase complex (OADHC). It is a thiamine diphosphate (ThDP)-dependent decarboxylase and a paralog of OGDH, the 2-oxoglutarate dehydrogenase E1. DHTKD1 catalyzes the first, rate-limiting and irreversible step of the complex: the oxidative decarboxylation of 2-oxoadipate (alpha-ketoadipate), transferring the decarboxylated glutaryl intermediate onto the lipoyl group of the shared E2 subunit (DLST), with the overall complex producing glutaryl-CoA and CO2. OADHC uses the same E2 (DLST) and E3 (DLD) components as the TCA-cycle 2-oxoglutarate dehydrogenase complex, but the E1 subunit is complex-specific; DHTKD1 strongly prefers 2-oxoadipate over 2-oxoglutarate as substrate. This reaction is the final common step of L-lysine, L-hydroxylysine and L-tryptophan degradation, whose convergent intermediate is 2-oxoadipate. The enzyme functions as a homodimer in the mitochondrial matrix. Loss-of-function variants cause alpha-aminoadipic and alpha-ketoadipic aciduria (AAKAD, frequently benign), and DHTKD1 has also been linked to axonal Charcot-Marie-Tooth disease type 2Q.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: Subcellular-location IEA placing DHTKD1 in the mitochondrion, consistent with all experimental evidence and the mitochondrial transit peptide. Correct but less precise than the mitochondrial matrix localization supported by Reactome/Ensembl orthology. Reason: DHTKD1 is a validated mitochondrial matrix enzyme (UniProt SUBCELLULAR LOCATION, PMID:23141294). The generic mitochondrion term is correct. Supporting Evidence: PMID:23141294 implicating an important role for DHTKD1 in mitochondrial energy production and neurological development. |
| GO:0016624 oxidoreductase activity, acting on the aldehyde or oxo group of donors, disulfide as acceptor | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: Broad InterPro/orthology-based oxidoreductase term describing the overall E1+E2+E3 (disulfide-acceptor) chemistry of the 2-oxo-acid dehydrogenase family. The precise activity of the E1a subunit is the ThDP-dependent decarboxylation captured by GO:0160166. Reason: This family-level term describes the full dehydrogenase complex reaction in which the ultimate electron acceptor is a disulfide (lipoyl/E3). The DHTKD1 E1a subunit itself performs ThDP-dependent decarboxylation of 2-oxoadipate and transfers the acyl group to the E2 lipoyl moiety; the more specific and accurate MF for DHTKD1 is GO:0160166 (2-oxoadipate dehydrogenase activity), which is separately annotated with IDA support. Supporting Evidence: PMID:29191460 It is involved in the oxidative decarboxylation of 2-oxoadipate (OA) to glutaryl-CoA on the final degradative pathway of L-lysine |
| GO:0030976 thiamine pyrophosphate binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-based annotation of thiamine diphosphate (ThDP) binding. ThDP is the essential catalytic cofactor of DHTKD1, confirmed biochemically and by crystal structures of the DHTKD1-ThDP complex. Reason: DHTKD1 is a ThDP-dependent decarboxylase; ThDP is documented as its cofactor (UniProt COFACTOR, PMID:32695416; DHTKD1-ThDP crystal structure PMID:32633484). The InterPro TPP-binding domain (IPR011603/IPR029061) is present. This is a core molecular function. Supporting Evidence: PMID:29191460 Herein are reported unique properties of the novel human thiamin diphosphate (ThDP)-dependent enzyme 2-oxoadipate dehydrogenase (hE1a) |
| GO:0160166 2-oxoadipate dehydrogenase activity | IEA GO_REF:0000116 | ACCEPT | Summary: RHEA-mapped IEA for the core catalytic activity of DHTKD1: the ThDP-dependent oxidative decarboxylation of 2-oxoadipate (RHEA:69576). This is the primary, experimentally validated molecular function. Reason: Matches the reaction assigned in UniProt (RHEA:69576) and is directly supported by biochemistry (PMID:29191460, PMID:32633484) and structure. Duplicate of the IDA-supported GO:0160166 below; both are correct. Supporting Evidence: PMID:29191460 hE1a displays an approximately 49-fold preference in catalytic efficiency for OA over OG, indicating that hE1a is specific to the 2-oxoadipate dehydrogenase complex |
| GO:0005515 protein binding | IPI PMID:28514442 Architecture of the human interactome defines protein commun... | MARK AS OVER ANNOTATED | Summary: High-throughput affinity-purification/mass-spectrometry interactome (BioPlex 2.0) IPI to PGLYRP3 (Q96LB9). Bare "protein binding" is uninformative about DHTKD1's molecular function. Reason: This is a proteome-scale AP-MS screen, not a directed study of DHTKD1's biology; the recorded partner (PGLYRP3) has no established functional relationship to 2-oxoadipate catabolism. Per curation guidance, bare GO:0005515 protein binding IPIs are uninformative and are marked as over-annotation rather than removed. The biologically meaningful interaction of DHTKD1 is with the E2 subunit DLST, captured by the oxoadipate dehydrogenase complex annotation. Supporting Evidence: PMID:28514442 BioPlex 2.0 exceeds previous experimentally derived interaction networks in depth and breadth |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | MARK AS OVER ANNOTATED | Summary: Binary yeast-two-hybrid interactome (HuRI) IPI to an isoform of BMAL1 (O00327-8). Bare "protein binding" is uninformative about DHTKD1's molecular function. Reason: This is a genome-scale binary interaction map, not a directed functional study of DHTKD1. The reported partner has no established role in 2-oxoadipate/lysine catabolism. Per curation guidance, bare protein binding IPIs are marked as over-annotation rather than removed. Supporting Evidence: PMID:32296183 A reference map of the human binary protein interactome. |
| GO:0005515 protein binding | IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... | MARK AS OVER ANNOTATED | Summary: High-throughput AP-MS interactome (BioPlex-derived, cell-specific networks) IPI to PGLYRP3 (Q96LB9). Bare "protein binding" is uninformative about DHTKD1's molecular function. Reason: Proteome-scale interactome dataset rather than a directed DHTKD1 study; the reported partner has no established connection to 2-oxoadipate catabolism. Per curation guidance, bare protein binding IPIs are marked as over-annotation rather than removed. Supporting Evidence: PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000107 | ACCEPT | Summary: Orthology-based (Ensembl Compara) is_active_in annotation to the mitochondrial matrix, transferred from mouse ortholog. Consistent with the matrix localization of a soluble ThDP-dependent dehydrogenase. Reason: DHTKD1 has an N-terminal mitochondrial transit peptide and functions as a soluble matrix enzyme of the OADHC; matrix localization is supported by Reactome and by the shared architecture with the OGDH complex. Supporting Evidence: PMID:29191460 the dihydrolipoyl succinyltransferase (hE2o) and the dihydrolipoyl dehydrogenase (hE3) components of the tricarboxylic acid cycle 2-oxoglutarate dehydrogenase complex (OGDHc) for its activity |
| GO:0009063 amino acid catabolic process | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Orthology-based involvement in amino acid catabolism. Correct but a generic parent of the specific L-lysine/L-tryptophan catabolic processes DHTKD1 participates in. Reason: Accurate at a high level (DHTKD1 acts on the convergent 2-oxoadipate step of lysine/hydroxylysine/tryptophan degradation) but subsumed by the more specific L-lysine catabolic process (GO:0019477). Retained as non-core background rather than as a distinct core function. Supporting Evidence: PMID:29191460 on the final degradative pathway of L-lysine and is critical for mitochondrial metabolism |
| GO:0019477 L-lysine catabolic process | IEA GO_REF:0000107 | ACCEPT | Summary: Orthology-based annotation to L-lysine catabolism. This is the principal biological process in which DHTKD1 acts, catalyzing the final common 2-oxoadipate step of the lysine (and hydroxylysine/tryptophan) degradation pathway. Reason: Well supported: DHTKD1 performs the rate-limiting decarboxylation of 2-oxoadipate, the convergent intermediate of L-lysine catabolism; disease variants cause elevated 2-oxoadipate/2-aminoadipate. Core process. Supporting Evidence: PMID:29191460 It is involved in the oxidative decarboxylation of 2-oxoadipate (OA) to glutaryl-CoA on the final degradative pathway of L-lysine |
| GO:0005739 mitochondrion | IDA GO_REF:0000052 | ACCEPT | Summary: Immunofluorescence-based (HPA) IDA localizing DHTKD1 to the mitochondrion. Consistent with all other evidence. Reason: Directly observed mitochondrial localization by immunofluorescence, concordant with the mitochondrial matrix function of the OADHC E1a subunit. Supporting Evidence: PMID:23141294 implicating an important role for DHTKD1 in mitochondrial energy production and neurological development. |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: High-throughput mitochondrial proteomics (MitoCoP) detecting DHTKD1 in the high-confidence human mitochondrial proteome. Reason: Independent proteomic confirmation of mitochondrial localization, consistent with the transit peptide and matrix function. Supporting Evidence: PMID:34800366 defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP) |
| GO:0160166 2-oxoadipate dehydrogenase activity | IDA PMID:29191460 The mitochondrial 2-oxoadipate and 2-oxoglutarate dehydrogen... | ACCEPT | Summary: Direct biochemical demonstration that recombinant human E1a (DHTKD1) oxidatively decarboxylates 2-oxoadipate, with ~49-fold catalytic preference for 2-oxoadipate over 2-oxoglutarate. This is the defining, experimentally validated molecular function of the gene. Reason: Gold-standard IDA evidence for the core catalytic activity; corroborated by kinetics (KM 0.012-0.015 mM for 2-oxoadipate) and crystal structures (PMID:32633484, PMID:32695416). Supporting Evidence: PMID:29191460 hE1a displays an approximately 49-fold preference in catalytic efficiency for OA over OG, indicating that hE1a is specific to the 2-oxoadipate dehydrogenase complex |
| GO:0160167 oxoadipate dehydrogenase complex | IDA PMID:29191460 The mitochondrial 2-oxoadipate and 2-oxoglutarate dehydrogen... | ACCEPT | Summary: DHTKD1 is the E1a subunit of the 2-oxoadipate dehydrogenase complex, which it forms together with the shared E2 (DLST) and E3 (DLD) components of the 2-oxoglutarate dehydrogenase machinery. Directly demonstrated by reconstitution of an active complex. Reason: Core cellular-component annotation. DHTKD1 recruits E2 (DLST) and E3 (DLD) to assemble a functional OADHC; the E1 subunit is complex-specific. This is the biologically meaningful protein-protein assembly for DHTKD1. Supporting Evidence: PMID:29191460 The hE1a has recruited the dihydrolipoyl succinyltransferase (hE2o) and the dihydrolipoyl dehydrogenase (hE3) components of the tricarboxylic acid cycle 2-oxoglutarate dehydrogenase complex (OGDHc) for its activity |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9858321 | ACCEPT | Summary: Reactome TAS localizing the DHTKD1-catalyzed 2-oxoadipate decarboxylation to the mitochondrial matrix, the compartment of the OADHC. Reason: Consistent with the soluble matrix location of the E1a subunit of the OADHC and with orthology/proteomic evidence. Supporting Evidence: PMID:29191460 the tricarboxylic acid cycle 2-oxoglutarate dehydrogenase complex (OGDHc) for its activity |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9858589 | ACCEPT | Summary: Reactome TAS localizing the OADHC E3 (DLD) dihydrolipoyl dehydrogenation step to the mitochondrial matrix, the compartment where DHTKD1 acts. Reason: Matrix localization is well established for the OADHC in which DHTKD1 is the E1 subunit. Supporting Evidence: PMID:29191460 the dihydrolipoyl dehydrogenase (hE3) components of the tricarboxylic acid cycle 2-oxoglutarate dehydrogenase complex (OGDHc) for its activity |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-9858590 | ACCEPT | Summary: Reactome TAS localizing the OADHC E2 (DLST) glutaryl transfer to CoA in the mitochondrial matrix, the compartment where DHTKD1 acts. Reason: Consistent with matrix localization of the OADHC and of DHTKD1. Supporting Evidence: PMID:29191460 the dihydrolipoyl succinyltransferase (hE2o) and the dihydrolipoyl dehydrogenase (hE3) components of the tricarboxylic acid cycle 2-oxoglutarate dehydrogenase complex (OGDHc) for its activity |
| GO:0005739 mitochondrion | IDA PMID:23141294 A nonsense mutation in DHTKD1 causes Charcot-Marie-Tooth dis... | ACCEPT | Summary: IDA localizing DHTKD1 to the mitochondrion, from the study that established the DHTKD1-CMT2 link and reported subcellular localization. Reason: Direct experimental evidence for mitochondrial localization (UniProt SUBCELLULAR LOCATION cites this paper); concordant with all other data. Supporting Evidence: PMID:23141294 implicating an important role for DHTKD1 in mitochondrial energy production and neurological development. |
| GO:0006091 generation of precursor metabolites and energy | IMP PMID:23141294 A nonsense mutation in DHTKD1 causes Charcot-Marie-Tooth dis... | MARK AS OVER ANNOTATED | Summary: IMP from a DHTKD1-silencing study reporting decreased ATP and total NAD(+)/NADH. This is a downstream physiological consequence of losing a lysine-catabolic enzyme rather than a direct biological process of DHTKD1. Reason: DHTKD1 knockdown reduces cellular ATP/NAD(H) (an indirect metabolic readout), but DHTKD1 is not part of primary energy-generating machinery such as the TCA cycle or oxidative phosphorylation; its direct role is the 2-oxoadipate step of amino-acid (lysine/tryptophan) catabolism. This term over-generalizes a secondary phenotype. Note this contrasts with the OGDH paralog, which is a bona fide TCA-cycle energy enzyme. Retained (not removed) as it derives from an experimental IMP. Supporting Evidence: PMID:23141294 DHTKD1 silencing was found to lead to impaired energy production, evidenced by decreased ATP, total NAD(+) and NADH, and NADH levels |
| GO:0006569 L-tryptophan catabolic process | IEA PMID:29191460 The mitochondrial 2-oxoadipate and 2-oxoglutarate dehydrogen... | NEW | Summary: Proposed additional biological-process annotation. 2-oxoadipate is the convergent intermediate of L-lysine, L-hydroxylysine AND L-tryptophan catabolism; by decarboxylating 2-oxoadipate, DHTKD1 catalyzes the final common step of the tryptophan degradation pathway as well as the lysine pathway. Reason: UniProt explicitly states DHTKD1 is responsible for the last step of L-lysine, L-hydroxylysine and L-tryptophan catabolism (common product 2-oxoadipate). The tryptophan-catabolic role is not otherwise captured in GOA and complements the existing L-lysine catabolic process annotation. Supporting Evidence: PMID:29191460 It is involved in the oxidative decarboxylation of 2-oxoadipate (OA) to glutaryl-CoA on the final degradative pathway of L-lysine |
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Download this section (compressed HTML)Q: Given that DHTKD1 shares E2 (DLST) and E3 (DLD) with the 2-oxoglutarate dehydrogenase complex, how is flux partitioned between the OGDHC and OADHC in tissues where both are expressed (e.g. liver)?
Q: Why is alpha-aminoadipic/alpha-ketoadipic aciduria caused by DHTKD1 loss so frequently asymptomatic, and what genetic or metabolic factors modify the CMT2Q neuropathy phenotype?
Experiment: Tissue-resolved metabolic flux analysis (e.g. 13C-lysine tracing) in DHTKD1-knockout versus wild-type cells to quantify the contribution of DHTKD1 to 2-oxoadipate turnover and downstream glutaryl-CoA and energy metabolism.
Hypothesis: DHTKD1 loss diverts 2-oxoadipate away from glutaryl-CoA, causing measurable accumulation of 2-oxoadipate/2-aminoadipate without major bioenergetic deficit.
Experiment: Structural and kinetic characterization of the assembled DHTKD1-DLST-DLD megacomplex to define substrate channeling and the effect of AAKAD variants (e.g. G729R, R715C) on complex assembly and activity.
Hypothesis: AAKAD-causing variants impair DHTKD1-DLST assembly, disrupting intermediate channeling rather than abolishing intrinsic decarboxylase chemistry.
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