Immunochemical evidence for the participation of cytochrome b 5 in the NADH synergism of the NADPH-dependent mono-oxidase system of hepatic microsomes

Abstract

Anti-cytochrome b 5 immunoglobulin (AIg) from a rabbit was used to establish the role of cytochrome b 5 in the transfer of electrons from NADH or NADPH to the hepatic microsomal mono-oxidase system of the rat. AIg inhibited ethylmorphine (EM) N-demethylase when both NADH and NADPH were present, but had little effect when NADPH was the only source of electrons. Inhibition was reversed when AIg was preincubated with pure cytochrome b 5. Specificity of AIg was shown by its inhibitory effect on NADH cytochrome c reductase activity; it was without effect on NADPH-cytochrome P-450 reductase or aniline hydroxylase activities. It is concluded that the second electron required for EM N-demethylation can be donated by NADH via cytochrome b 5.