a mitochondrial matrix enzyme that catalyzes the oxidative decarboxylation of pyruvate, producing acetyl-CoA and CO2. A key enzyme in controlling the balance between lipid and glucose oxidation depending on substrate availability. The pyruvate dehydrogenase (PDH) holoenzyme is a multi-enzyme complex (PDHC) that contains 20-30 copies of pyruvate decarboxylase tetramers (2 alpha:2 beta)(E1), 60 copies of dihydrolipoamide acetyltransferase (E2), six homodimers of dihydrolipoamide dehydrogenase (E3), plus E3 binding proteins. The activity of PDH is tightly regulated by phosphorylation. The phosphorylation of at least one of three specific serine residues in E1 subunit by PDHK inactivates the PDHC, while dephosphorylation by PDP restores its activity. Sites 1, 2, and 3 of PDHA1 are S293, S300, and S232, respectively. Four PDHK isoenzymes have been described, each with different site specificity: all four phosphorylate sites 1 and 2 but at different rates; for site 1 PDHK2 >PDHK4 >PDHK1 >PDHK3; for site 2, PDHK3> PDHK4 > PDHK2 > PDHK1. Only PDHK1 phosphorylates site 3. PDHA1 deficiency is the most common enzyme defect in patients with primary lactic acidosis. Note: This description may include information from UniProtKB.
SS: The number of records in which this modification site was determined using site-specific methods. SS methods include amino acid sequencing, site-directed mutagenesis, modification site-specific antibodies, specific MS strategies, etc.