title: The role of cytochrome b5 in mixed function oxidations: effect of microsomal binding of the hemoprotein on hepatic N-demethylations.
abstract: Incubation of rat cytochrome b5 (D-b5) with rat liver microsomes resulted in specific binding of the hemoprotein. The bound hemoprotein was rapidly reduced by NADH. The NADH cytochrome c reductase activity in these preparations increased in proportion to the amount of cytochrome. In contrast to D-b5, which inhibited N-demethylation and the NADH synergism, the binding of cytochrome b5 preparations, reconstituted from heme and apocytochrome b5 had no effect on either the NADPH-dependent N-demethylation of aminopyrine or ethylmorphine or the NADH synergism observed with rat liver microsomes. In addition, manganese protoporphyrin-apocytochrome complex, when bound to microsomes in amounts equilvalent to D-b5, showed no effect on N-demethylation activity. These results suggest that homogeneous cytochrome b5 contains contaminating amounts of tightly bound detergent which presumably is removed during the extraction of the heme from the apocytochrome.
mesh_terms: D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D001059:Apoproteins / Q000378:metabolism; D003579:Cytochrome Reductases / Q000378:metabolism; D003574:Cytochrome c Group; D003580:Cytochromes / Q000302:isolation & purification / Q000378:metabolism*; D005037:Ethylmorphine-N-Demethylase / Q000378:metabolism; D006420:Hemeproteins / Q000378:metabolism*; D008297:Male; D008345:Manganese / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism*; D011485:Protein Binding; D011524:Protoporphyrins / Q000378:metabolism; D051381:Rats; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors
chemical_list: D001059:Apoproteins; D003574:Cytochrome c Group; D003580:Cytochromes; D006420:Hemeproteins; D011524:Protoporphyrins; D000632:Aminopyrine; D009243:NAD; D012967:Sodium Dodecyl Sulfate; D008345:Manganese; D010089:Oxidoreductases, N-Demethylating; D005037:Ethylmorphine-N-Demethylase; D003579:Cytochrome Reductases