Oxidation of reduced triphosphopyridine nucleotide by submitochondrial particles from beef heart

Submitochondrial particles prepared from beef heart are capable of oxidizing TPNH, in the absence of added DPN, at a rate of approximately 50 nmoles/min × mg protein at 30°. TPNH oxidation by these particles occurs through the respiratory chain as evidenced from TPNH-induced reduction of the cytochromes and the inhibitory effects of rotenone, piericidin A, amytal, antimycin A and cyanide. The latter studies have indicated that the site of TPNH interaction with the respiratory chain is on the substrate side of the rotenone-piericidin block and close to that of DPNH.