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 PDHA2; it is reactivated by dephosphorylation. Heterotetramer of two PDHA2 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). Testis.