the E2 component of the pyruvate dehydrogenase complex (PDHC) that catalyzes the overall conversion of pyruvate to acetyl-CoA and CO2. Contains two lipoyl-binding domains. The PDHC plays a major role in controlling the balance between lipid and glucose oxidation depending on substrate availability. The activity of the PDHC is tightly regulated by phosphorylation of the E1 components by the PDHKs. 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 homo-dimers of dihydrolipoamide dehydrogenase (E3), plus E3 binding proteins. PDHKs are recruited to the PDHC by binding to a lipoyl group covalently attached to K174 of the inner lipoyl domain of the E2 component. Note: This description may include information from UniProtKB.