Studies of the electron transport systems of heart muscle: biochemical and antigenic properties of a soluble DPNH dehydrogenase.

Highly purified DPNH dehydrogenase has been prepared from preparations of DPNH oxidaze. The enzyme has an average molecular weight of 80,000 and contains flavin, nonheme iron, and labile sulfide groups in an approximate ratio of 1:2:2, respectively. In electron paramagnetic resonance studies the dehydrogenase showed a g = 1.93 signal upon reduction with hydrosulfite, but not with DPNH, which suggests that the iron is not active in the enzymic catalysis. Studies of immunodiffusion and of enzyme inhibition with specific antibodies suggest that the DPNH dehydrogenase has not been grossly modified during preparation, and that it and the dehydrogenases prepared by the methods of King and Howard and Cremona and Kearney are related to each other and to preparations of DPNH oxidase.