Purification and properties of the Ascaris pyruvate dehydrogenase complex.

The pyruvate dehyhdrogenase complex (pyruvate:lipoate oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1) has been isolated from Ascaris muscle mitochondria and purified to near homogeneity by differential centrifugation, (NH4)2SO4 fractionation and calcium phosphate gel-cellulose chromatography. It is similar in shape, size and physical characteristics to pyruvate dehydrogenase complexes isolated from mammalian sources. It has an absolute dependence on CoA, NAD+ and pyruvate for activity and is competitively inhibited by acetyl-CoA and NADH. However, much higher NADH/NAD+ ratios are necessary to inhibit activity, suggesting regulation by the more reduced state of the pyridine nucleotide pool in Ascaris mitochondria.