Abstract
Lipoic acid-dependent and CoA- and NAD-linked oxidative decarboxylation of pyruvate and 2-oxoglutarate is the main pathway in mammals and proceeds via decarboxylation, acyl generation, acyl transfer and electron transfer.reaction sequences by the participation of several enzymes. In addition to CoA and NAD, TDP, a bivalent metal ion (Mg^<2+> or Ca^<2+>), protein-bound lipoic acid, and FAD are essential. Enzyme systems that catalyze this reaction have been isolated from pig heart Keilin-Hartree preparation as soluble and well-organized multienzyme complexes with molecular weights in the millions. These two complexes have been dissociated into their constituent enzymes, α-keto acid dehydrogenase, lipoate acyltransferase and lipoamide dehydrogenase, and have been reconstituted, both functionally and structurally, from their isolated component enzymes. The basic geometry of these complexes has been investigated from correlated biochemical and electron microscopic studies. Regulatory properties of both complexes are also discussed. (Received December 21,1970)
