[Characteristics of the interaction of adrenal lipoamide dehydrogenase with physiological and quinone electron acceptors].
Lipoamide dehydrogenase (EC 1.6.4.3) from the ketoglutarate dehydrogenase complex of adrenals catalyzes the oxidation of NADH by lipoamide and quinone compounds according to the "ping-pong" scheme. The catalytic constants of these reactions are equal to 220 and 24 s-1, respectively (pH 7.0). The maximal quinone reductase activity is observed at pH 5.6, whereas the lipoamide reductase activity changes insignificantly at pH 7.5-5.5. The maximal dihydrolipoamide-NAD+ reductase activity is observed at pH 7.8. The oxidative constants of quinone electron acceptors vary from 6 X 10(6) to 4 X 10(2) M-1 s-1 and increase with their redox potential. The patterns of NAD+ inhibition in the quinone reductase reaction differ from that of lipoamide reductase reaction. The quinones are reduced by lipoamide dehydrogenase in the one-electron mechanism.
D000311:Adrenal Glands / Q000201:enzymology*; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D011809:Quinones / Q000378:metabolism*
D011809:Quinones; D009243:NAD; D008058:Dihydrolipoamide Dehydrogenase
Zakonomernosti vzaimodeĭstviia lipoamiddegidrogenazy nadpochechnikov s fiziologicheskimi i khinonovymi aktseptorami élektronov.