Nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate-dependent reduction of mammalian hepatic microsomal cytochrome b5: Some properties of the enzyme system catalyzing the endogenous reduction of pyridine nucleotides

Abstract

1. 1. An enzyme system is present in mouse hepatic microsomes which is capable of reducing NAD + and NADP + and, consequently, of reducing cytochrome b 5 in the absence of other externally added cofactors. 2. 2. A similar enzyme system is also present in hepatic microsomes of rat and rabbit. 3. 3. The rates of reduction of cytochrome b 5 and auto-oxidation of reduced cytochrome b 5 were, however, much slower in NAD + supplemented reaction media than in those supplemented with NADH. 4. 4. The effects of sulfhydryl reagents, chelating agents and divalent cations are reported.