9078-32-4

A microsomal cytochrome involved in such metabolic activities as fatty acid desaturation. It may be involved in the reduction of cytochrome P450. The possibility that the second electron in cytochrome P450 reduction in vivo is derived from NADH via cytochrome b5 is still to be resolved. This pathway is not, however, essential for all cytochrome P450-dependent monooxygenations since many occur in in vitro systems reconstituted from purified NADPHcytochrome P450 reductase, cytochrome P450 and phosphatidylcholine in the presence of NADPH and oxygen. Nevertheless, cytochrome b5 is stimulatory for some monooxygenations and may facilitate oxidative activity in the intact endoplasmic reticulum.