Purification and Properties of Pigeon Breast Muscle α-Keto Acid Dehydrogenase Complexes

Publisher Website
Google Scholar
Abstract
The purification procedures for a-keto acid dehydrogenase complexes from pigeon breast muscle have been improved.The sedimentation coefficients, s020,w, were 77 S for pyruvate dehydrogenase complex and 43 S for 2-oxoglutarate dehydrogenase complex.The results of SDS-polyacrylamide gel electrophoresis and the ratios between the activities of the overall and component enzyme reactions of the purified preparation of pyruvate dehydrogenase complex indicate that the subunit structure of the pigeon breast muscle enzyme complex is nearly the same as that of the pig heart enzyme complex, except for a lower content of hpoamide dehydrogenase component. The data on 2-oxoglutarate dehydrogenase complex indicate that the pigeon breast muscle enzyme complex contained more 2-oxoglutarate dehydrogenase and less lipoate succinyltransferase than the pig heart complex. Michaelis constants for the reactants of the pyruvate dehydrogenase complex reaction were: pyruvate, 17 μ, Co A, 27 μM; NAD+, 200 μm. Those of the 2-oxoglutarate dehydrogenase complex reaction were: 2-oxoglutarate, 150 μm; CoA, 14 μm; NAD+, 120 μM. Products, acetyl-CoA, succinyl-CoA and NADH, were competitive inhibitors with respect to the corresponding substrates.Kynurenate and xanthurenate inhibited the activities of the two enzyme complexes by acting on the lipoamide dehydrogenase component.