Analysis of debromination of 1,2-dibromoethane by cytochrome P-450-linked hydroxylation systems as observed by bromide electrode.
Debromination of 1,2-dibromoethane (DBE) by a rabbit liver microsomal preparation and a reconstituted cytochrome P-450 enzyme system was investigated. The reaction was performed in our newly constructed reaction vessel, in which a bromide electrode was installed. During the reaction, the liberated bromide ion was continuously measured by the bromide electrode, and the amount was recorded. In the microsomal preparation, the DBE-debromination rate per nmol cytochrome P-450 was enhanced by phenobarbital-pretreatment of rabbits compared with the untreated microsomes, whereas it was diminished by 3-methylcholanthrene-pretreatment. The debromination reaction was reconstituted in a purified enzyme system containing phenobarbital-inducible rabbit liver microsomal cytochrome P-450 (P-450PB), NADPH-cytochrome P-450 reductase, and NADPH. The optimum conditions required the presence of dilauroylphosphatidylcholine and cytochrome b5. Cytochrome b5 was found not to be an obligatory component for the DBE-debromination in the reconstituted system, but it stimulated the activity about 3.4-fold. Preincubation of the reconstituted mixture with guinea pig anti-cytochrome P-450PB antiserum markedly inhibited the debromination reaction.
D000818:Animals; D001965:Bromides / Q000032:analysis*; D001966:Bromine / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004566:Electrodes; D004789:Enzyme Activation / Q000187:drug effects; D015946:Ethylene Dibromide / Q000032:analysis*; D006168:Guinea Pigs; D006842:Hydrocarbons, Brominated / Q000032:analysis*; D006900:Hydroxylation; D066298:In Vitro Techniques; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology; D010634:Phenobarbital / Q000494:pharmacology; D011817:Rabbits
D001965:Bromides; D006842:Hydrocarbons, Brominated; D015946:Ethylene Dibromide; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D001966:Bromine; D010634:Phenobarbital