A high-spin form of cytochrome P-450 highly purified from polychlorinated biphenyl-treated rats. Catalytic characterization and immunochemical quantitation in liver microsomes.
A high-spin form of cytochrome P-450 (termed PCB P-448-H) was purified from liver microsomes of polychlorinated biphenyl (PCB)-treated rats to homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This high-spin form of cytochrome P-450 was distinguishable from a low-spin form of cytochrome P-450 (PCB P-448-L) purified from microsomes of PCB-treated rats by the criteria of molecular weights, peptide mapping, and immunochemical properties. In addition, PCB P-448-H catalyzed the hydroxylation of acetanilide (position 4) and biphenyl (positions 2 and 4), and N-hydroxylation of the promutagens 3-amino-1-methyl-5H-pyrido(4,3-b)indole (Trp-P-2), 2-amino-6-methyl-dipyrido(1,2-alpha:3',2'-d)imidazole (Glu-P-1), 2-aminofluorene, and 4-aminobiphenyl at much faster rates than did PCB P-448-L. These promutagens and aflatoxin B1 were efficiently metabolized to mutagens by this high-spin form of hemoprotein. Rabbit immunoglobulin G (IgG) raised against PCB P-448-H inhibited the microsomal O-depropylation activity of p-propoxyaniline. Radial immunodiffusion assay with the IgG showed that PCB P-448-H was one of the major forms of cytochrome P-450 in liver microsomes of PCB-treated rats. On the basis of these results, we propose that this high-spin form of cytochrome P-450 is a key enzyme activating a variety of environmental promutagens in the 9000 x g supernatant fraction of PCB-treated rats, which has been widely used as an activation system in routine mutation tests.
D000818:Animals; D001711:Biotransformation; D002384:Catalysis; D019388:Cytochrome P-450 CYP1A2; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification*; D003580:Cytochromes / Q000302:isolation & purification; D005260:Female; D006900:Hydroxylation; D007120:Immunochemistry; D005779:Immunodiffusion; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D009153:Mutagens / Q000378:metabolism*; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D003580:Cytochromes; D009153:Mutagens; D003577:Cytochrome P-450 Enzyme System; D011078:Polychlorinated Biphenyls; C017170:Cyp1a2 protein, rat; D019388:Cytochrome P-450 CYP1A2