Analysis of Debromination of 1, 2-Dibromoethane by Cytochrome P-450-Linked Hydroxylation Systems as Observed by Bromide Electrode

抄録

Debromination of l, 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-met hylcholanthrene-pretreatment. The debromination reaction was reconstituted in a purified enzyme system containing phenobarbital-inducible rabbit liver microsomal cytochrome P-450 (P450PB), 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-debromi nation 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.