Position specificity in n-hexane hydroxylation by two forms of cytochrome P-450 in rat liver microsomes.
The hydroxylation of n-hexane by rat liver microsomes was studied and the contribution of different molecular species of cytochrome P-450 to the hydroxylation reaction was examined. In the case of untreated rats, the products of NADPH-dependent n-hexane hydroxylation were 1-, 2-, and 3-hexanols, and the major one was 2-hexanol. Phenobarbital (PB) treatment of animals resulted in a significant increase of the hydroxylation activity. The formation of 2- and 3-hexanols was much more significantly increased than that of 1-hexanol. On the other hand, 3-methylcholanthrene (MC) treatment stimulated the formation of 3-hexanol and the formation of the other two isomeric alcohols was rather decreased. These observations suggested the position specificities of the PB-inducible form (P-450(PB)) and MC-inducible form (P-450(MC)) of cytochrome P-450 in the hydroxylation of n-hexane. Inhibition experiments using antibodies specific to P-450(PB) and P-450(MC) also indicated that P-450(PB) was more active in the hydroxylation at the 2-position whereas P-450(MC) was more specific for the 3-position. NADPH-dependent n-hexane hydroxylation systems were reconstituted by the use of purified NADPH-cytochrome P-450 reductase and P-450(PB) or P-450(MC), and the activities of the reconstituted systems supported the proposed position specificities of these two forms of cytochrome P-450 in n-hexane hydroxylation.
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D006586:Hexanes / Q000378:metabolism*; D006900:Hydroxylation; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D006586:Hexanes; D007527:Isoenzymes; C026385:n-hexane; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase