The pyruvate dehydrogenase complex catalyzes the overall conversion of pyruvate to acetyl-CoA and CO(2), and thereby links the glycolytic pathway to the tricarboxylic cycle. (R)-N(6)-lipoyl-L-lysyl-[dihydrolipoyllysine-residue acetyltransferase] + H(+) + pyruvate = (R)-N(6)-(S(8)-acetyldihydrolipoyl)-L-lysyl-[dihydrolipoyllysine-residue acetyltransferase] + CO2 Pyruvate dehydrogenase activity is inhibited by phosphorylation of PDHA1; it is reactivated by dephosphorylation. Heterotetramer of two PDHA1 and two PDHB subunits. The heterotetramer interacts with DLAT, and is part of the multimeric pyruvate dehydrogenase complex that contains multiple copies of pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (DLAT, E2) and lipoamide dehydrogenase (DLD, E3). These subunits are bound to an inner core composed of about 48 DLAT and 12 PDHX molecules (By similarity). Phosphorylation at Ser-232, Ser-293 and Ser-300 by PDK family kinases inactivates the enzyme; for this phosphorylation at a single site is sufficient. Phosphorylation at Ser-293 interferes with access to active site, and thereby inactivates the enzyme. Dephosphorylation at all three sites, i.e. at Ser-232, Ser-293 and Ser-300, is required for reactivation (By similarity). Acetylation alters the phosphorylation pattern. Deacetylated by SIRT3 (By similarity).