Incorporation of Radioactive Iron into Cytochromeb5and Cytochrome P-450 of Liver Microsomes

摘要

1. A method of examining incorporation of radioactive iron into two types of microsomal hemeproteins, cytochromeb5and cytochrome P-450, is described.2. Radioactive iron was incorporated into P-450 more rapidly than into cytochromeb5, and radioactivity disappeared from the former more than twice as rapidly as from the latter.3. The turnover rate of cytochromeb5observed after injection of radio-iron was significantly different from that reported using14C-leucine, but similar to that recently reported using3H-δ-aminolevulinate.4. The disparity between the data obtained with these different methods could be ascribed to an exchange between free heme and that bound to cytochromeb5. This exchange was demonstratedin vitroby incubating radioactive heme and intact microsomes