Contains thiamine diphosphate. It is a component (in multiple copies) of the multienzyme pyruvate dehydrogenase complex in which it is bound to a core of molecules of EC
2.3.1.12, dihydrolipoyllysine-residue acetyltransferase, which also binds multiple copies of EC
1.8.1.4, dihydrolipoyl dehydrogenase. It does not act on free lipoamide or lipoyllysine, but only on the lipoyllysine residue in EC
2.3.1.12.