Purification and characterization of cytochrome P-450 induced by benz(a)anthracene in mouse skin microsomes.
Topical application of benz(a)anthracene to mouse skin elicited a 2-fold increase in cytochrome P-450 content, with accompanying increases in monooxygenase activities such as benzo(a)pyrene hydroxylation, 7-ethoxycoumarin O-deethylation, and acetanilide 4-hydroxylation, in the microsomes. A major form of cytochrome P-450 was purified from skin microsomes of mice treated with polycyclic aromatic hydrocarbon. A specific content of 1.95 nmol/mg of protein, which corresponded to 48-fold purification from the microsomes, was observed. The purified protein produced a single major band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis having a molecular weight of 55,000. Using Western blotting, the band immunochemically cross-reacted with antibody which had been raised against rat liver cytochrome P-450MC-1. The purified preparation efficiently catalyzed benzo(a)pyrene hydroxylation and 7-ethoxycoumarin O-deethylation when reconstituted with NADPH-cytochrome P-450 reductase. These activities were inhibited by 7,8-benzoflavone as well as anti-cytochrome P-450MC-1 antibody, but not by P-450PB-1 antibody. The results indicate that, in mouse skin microsomes, a cytochrome P-450 induced by benz(a)anthracene is enzymatically and immunochemically similar to rat liver cytochrome P-450MC-1. It is suggested that this enzyme plays an important role in the activation of carcinogenic polycyclic aromatic hydrocarbons.
Ichikawa
T
T
Department of Oral and Maxillofacial Surgery, Hiroshima University School of Dentistry, Japan.
Hayashi
S
S
Noshiro
M
M
Takada
K
K
Okuda
K
K
D000818:Animals; D001551:Benz(a)Anthracenes / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000302:isolation & purification; D004790:Enzyme Induction; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D008970:Molecular Weight; D012016:Reference Values; D012867:Skin / Q000187:drug effects / Q000378:metabolism*
D001551:Benz(a)Anthracenes; D003577:Cytochrome P-450 Enzyme System; C030935:benz(a)anthracene