Mitochondrial pyruvate fates — pyruvate dehydrogenase complex and pyruvate carboxylase

The two committed mitochondrial fates of pyruvate (imported from glycolysis via the mitochondrial pyruvate carrier). (1) Oxidative decarboxylation by the pyruvate dehydrogenase complex (PDC) links glycolysis to the TCA cycle: pyruvate + CoA + NAD+ -> acetyl-CoA + CO2 + NADH. The PDC is a giant mitochondrial-matrix multienzyme machine built on a 60-mer E2 (DLAT) core, with the thiamine-pyrophosphate-dependent E1 decarboxylase (an alpha2-beta2 heterotetramer of PDHA1 and PDHB), the E3-binding structural subunit PDHX (component X) that anchors the shared E3 dihydrolipoyl dehydrogenase (DLD), and DLD itself which reoxidises the lipoyl arms (passing electrons to NAD+). PDC flux is switched off by phosphorylation of E1alpha (by the pyruvate dehydrogenase kinases PDK1-4) and on by dephosphorylation (by the phosphatases PDP1/2). (2) Carboxylation by the biotin-dependent pyruvate carboxylase (PC): pyruvate + HCO3- + ATP -> oxaloacetate, the principal anaplerotic reaction replenishing TCA-cycle oxaloacetate and the committed first step of gluconeogenesis from pyruvate/lactate; PC is allosterically activated by acetyl-CoA (the PDC product), coordinating the two fates. Inherited defects cause severe lactic acidosis and neurological disease: PDHA1 (X-linked, the commonest), PDHB, DLAT and PDHX deficiencies cause pyruvate dehydrogenase complex deficiency (Leigh syndrome spectrum), and PC deficiency causes lactic acidosis with hypoglycemia; DLD deficiency (the shared E3) gives a combined phenotype (see the BCAA and homocysteine/cobalamin contexts).

MODULE:pyruvate_metabolismDRAFTMetabolic Pathwaymodules/pyruvate_metabolism.yaml
pyruvate metabolic processGO:0006090
GO:0006090
pyruvate metabolic process
The module is grounded in the GO pyruvate metabolic process (GO:0006090), covering the oxidative-decarboxylation (PDC) and carboxylation (PC) fates.
Reactome:R-HSA-70268
Pyruvate metabolism
Reaction stoichiometries follow the human Reactome pyruvate-metabolism reactions R-HSA-9861559 (PDC synthesizes acetyl-CoA from pyruvate) and R-HSA-70501 (PC carboxylates pyruvate to oxaloacetate).
file:human/PDHA1/PDHA1-ai-review.yaml
PDHA1 gene review (human)
The PDC E1-alpha grounding (UniProtKB:P08559, GO:0004739 pyruvate dehydrogenase (acetyl-transferring) activity, GO:0045254 complex) matches the completed human PDHA1 review.
file:human/PDHB/PDHB-ai-review.yaml
PDHB gene review (human)
The PDC E1-beta grounding (UniProtKB:P11177, GO:0004739, GO:0045254) matches the completed human PDHB review.
file:human/DLAT/DLAT-ai-review.yaml
DLAT gene review (human)
The PDC E2 core grounding (UniProtKB:P10515, GO:0004742 dihydrolipoyllysine- residue acetyltransferase activity, GO:0045254) matches the completed human DLAT review.
file:human/PDHX/PDHX-ai-review.yaml
PDHX gene review (human)
The E3-binding structural subunit grounding (UniProtKB:O00330, GO:0030674 protein-macromolecule adaptor activity, GO:0045254) matches the completed human PDHX review (a non-catalytic scaffold anchoring DLD).
file:human/DLD/DLD-ai-review.yaml
DLD gene review (human)
The shared E3 grounding (UniProtKB:P09622, GO:0004148 dihydrolipoyl dehydrogenase (NADH) activity) matches the completed human DLD review.
file:human/PC/PC-ai-review.yaml
PC gene review (human)
The pyruvate carboxylase grounding (UniProtKB:P11498, GO:0004736 pyruvate carboxylase activity) matches the completed human PC review.
3Nodes
2Parts
0Variant Sets
0Variants
6Annotons
1Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:pyruvate_metabolism deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Gene-review completeness (6/6 grounded genes reviewed)

6 complete review(s) · 1 with deep research · 0 missing review · 5 reviewed but lacking deep research

Gene Review Complete Deep research
DLAT P10515 ✓ ✓ ✗
DLD P09622 ✓ ✓ ✓
PC P11498 ✓ ✓ ✗
PDHA1 P08559 ✓ ✓ ✗
PDHB P11177 ✓ ✓ ✗
PDHX O00330 ✓ ✓ ✗

Details

Context
mitochondrial matrixGO:0005759
Mitochondrial pyruvate metabolism (PDC + pyruvate carboxylase)Metabolic Pathwaypyruvate_metabolism
pyruvate metabolic processGO:0006090
Context
mitochondrial matrixGO:0005759

The two committed mitochondrial fates of pyruvate, grounded to the human enzymes of the pyruvate dehydrogenase complex — PDHA1 (UniProtKB:P08559) and PDHB (P11177) of E1 (GO:0004739, EC 1.2.4.1), the E2 core DLAT (P10515, GO:0004742, EC 2.3.1.12), the E3-binding structural subunit PDHX (O00330, GO:0030674) and the shared E3 DLD (P09622, GO:0004148, EC 1.8.1.4), assembled as GO:0045254 — and pyruvate carboxylase PC (P11498, GO:0004736, EC 6.4.1.1). GO molecular-function/cellular-component terms were taken from the human GOA records; Reactome reaction ids and titles were verified against the local reactome cache. Each step uses a PANTHER family selector (generic over paralogs and orthologs) plus a concrete human representative member; the PDC is modelled as a PROTEIN_COMPLEX node with its five subunit types. PDHX is deliberately grounded as a non-catalytic adaptor (its E2-type catalytic His is replaced by Ser); DLD is the shared E3 of multiple 2-oxoacid dehydrogenase complexes. Upstream, pyruvate comes from glycolysis (via the mitochondrial pyruvate carrier); downstream, PDC-derived acetyl-CoA and PC-derived oxaloacetate feed the TCA cycle, and PC also feeds gluconeogenesis. PDC activity is phospho-regulated by the PDK kinases / PDP phosphatases (not modelled here).

Connections

pdc_step -> pc_step Positively Regulates
Acetyl-CoA produced by the PDC is the obligate allosteric activator of pyruvate carboxylase, coordinating the oxidative and anaplerotic fates of pyruvate (and, together, supplying acetyl-CoA + oxaloacetate for citrate synthesis / the TCA cycle).
Part 1: oxidative decarboxylation to acetyl-CoA (glycolysis-to-TCA gateway)
pyruvate + CoA + NAD+ to acetyl-CoA + CO2 + NADH (pyruvate dehydrogenase complex)Protein Complexpdc_step

Annotons

PDHA1: PDC E1 alpha (TPP decarboxylase)
pdha1_activity
Participant: Family: Pyruvate dehydrogenase E1 alpha family (PDHA1)
Family:
Pyruvate dehydrogenase E1 alpha family (PDHA1)PANTHER:PTHR11516
Representative Members: PDHA1 (human)UniProtKB:P08559

Function

pyruvate dehydrogenase (acetyl-transferring) activityGO:0004739
Substrates: pyruvate thiamine diphosphate (cofactor)
Products: (hydroxyethyl-TPP intermediate) carbon dioxide

Locations

mitochondrial matrixGO:0005759

TPP-dependent decarboxylase; with PDHB forms the alpha2-beta2 E1 that decarboxylates pyruvate and reductively acetylates the E2 lipoyl arm. The phosphoregulated subunit (PDK off / PDP on). X-linked; commonest PDC deficiency.

PDHB: PDC E1 beta
pdhb_activity
Participant: Family: Pyruvate dehydrogenase E1 beta / transketolase-like family (PDHB)
Family:
Pyruvate dehydrogenase E1 beta / transketolase-like family (PDHB)PANTHER:PTHR11624
Representative Members: PDHB (human)UniProtKB:P11177

Function

pyruvate dehydrogenase (acetyl-transferring) activityGO:0004739

Locations

mitochondrial matrixGO:0005759

Beta subunit of the E1 heterotetramer; completes the TPP-binding active site with PDHA1. Deficiency causes PDC (E1-beta) deficiency.

DLAT: PDC E2 (dihydrolipoyl acetyltransferase core)
dlat_activity
Participant: Family: 2-oxoacid dehydrogenase E2 (dihydrolipoyl acyltransferase) family (DLAT)
Family:
2-oxoacid dehydrogenase E2 (dihydrolipoyl acyltransferase) family (DLAT)PANTHER:PTHR23151
Representative Members: DLAT (human)UniProtKB:P10515

Function

dihydrolipoyllysine-residue acetyltransferase activityGO:0004742
Substrates: S-acetyl-dihydrolipoyl intermediate coenzyme A
Products: acetyl-CoA

Locations

mitochondrial matrixGO:0005759

Lipoyl-bearing E2 subunit forming the 60-mer structural core of the PDC; transfers the acetyl group from the lipoyl arm to CoA, yielding acetyl-CoA. Deficiency causes PDC (E2) deficiency; also a primary biliary cholangitis autoantigen.

PDHX: PDC component X / E3-binding protein (structural)
pdhx_activity
Participant: Family: 2-oxoacid dehydrogenase E3-binding-protein family (PDHX)
Family:
2-oxoacid dehydrogenase E3-binding-protein family (PDHX)PANTHER:PTHR23151
Representative Members: PDHX (human)UniProtKB:O00330

Function

protein-macromolecule adaptor activityGO:0030674

Locations

mitochondrial matrixGO:0005759

Structural E3-binding subunit (component X): built into the E2 core, it binds and positions the shared E3 (DLD). Not a classic enzyme (catalytically dead). Deficiency causes PDC (E3BP) deficiency.

DLD: shared E3 (dihydrolipoyl dehydrogenase)
dld_activity
Participant: Family: Dihydrolipoyl dehydrogenase / pyridine-nucleotide-disulphide oxidoreductase family (DLD)
Family:
Dihydrolipoyl dehydrogenase / pyridine-nucleotide-disulphide oxidoreductase family (DLD)PANTHER:PTHR22912
Representative Members: DLD (human)UniProtKB:P09622

Function

dihydrolipoyl dehydrogenase (NADH) activityGO:0004148
Substrates: dihydrolipoyl-E2 (reduced lipoyl arm) NAD+
Products: lipoyl-E2 (reoxidised) NADH

Locations

mitochondrial matrixGO:0005759

FAD-dependent E3 that reoxidises the dihydrolipoyl arm, passing electrons to NAD+. The common E3 shared with the 2-oxoglutarate and branched-chain 2-oxoacid dehydrogenase complexes and the glycine cleavage system (see the BCAA catabolism module).

Part 2: anaplerotic / gluconeogenic carboxylation to oxaloacetate
pyruvate + HCO3- + ATP to oxaloacetate + ADP + PiReactionpc_step

Annotons

PC: pyruvate carboxylase (biotin-dependent)
pc_activity
Participant: Family: Pyruvate carboxylase family (PC)
Family:
Pyruvate carboxylase family (PC)PANTHER:PTHR43778
Representative Members: PC (human)UniProtKB:P11498

Function

pyruvate carboxylase activityGO:0004736
Substrates: pyruvate hydrogencarbonate ATP biotin (covalent cofactor)
Products: oxaloacetate ADP phosphate

Locations

mitochondrial matrixGO:0005759

Biotin-dependent homotetramer; the principal anaplerotic reaction (replenishing TCA oxaloacetate) and the committed first step of gluconeogenesis from pyruvate/lactate. Allosterically activated by acetyl-CoA (the PDC product). Deficiency causes pyruvate carboxylase deficiency (severe lactic acidosis, hypoglycemia).