The preparation and some properties of a reduced diphosphopyridine nucleotide dehydrogenase from the snake venom digest of a heartmuscle preparation.

Particulate preparations from mammalian heart which are able to transfer electrons in successive steps from reduced diphosphopyridine nucleotide (DPNH) to molecular oxygen or to intermediate components of the respiratory chain have been reported from time to time (1, 2). Likewise, lipid-free, soluble DPNH dehydrogenases have been obtained from sarcosomal particles. Among them, the diaphorase of Straub (3, 4) and the DPNH-cytochrome c reductase of Mahler (5, 6) have been extensively studied. Recently, it has been shown that diaphorase is actually a lipoyl dehydrogenase (7, 8). Indeed, the enzyme is a component of the cr-ketoglutaric dehydrogenase complex (9, 10). On the other hand, the status and physiological action of DPNH-cytochrome c reductase are still obscure. In the search for DPNH dehydrogenase in heart particles, another soluble enzyme has been isolated from the snake venom digest of the Keilin-Hartree preparation. This enzyme is different from the diaphorase of Straub. Although in certain aspects it resembles the reductase of Mahler, other properties have demonstrated the nonidentity of these two enzymes. This paper reports on the enzyme isolated from the snake venom digest of the heart muscle preparation with respect to its solubilization, purification, and properties. Differences from and relations with other soluble DPNH dehydrogenases are discussed. The effect of venom digestion of the heart muscle preparation on its oxidative capacities toward DPNH is also described. Preliminary reports (11-13) have already appeared.