Purification and characterization of two forms of 2,3,4,7,8-pentachlorodibenzofuran-inducible cytochrome P-450 in hamster liver.
Two forms of cytochrome P-450 (P-450) from liver microsomes of hamsters treated with 2,3,4,7,8-pentachlorodibenzofuran (PenCDF), which possesses the potent acute toxicity and 3-methylcholanthrene (MC)-type inducing ability of liver microsomal monooxygenases in animals, were purified and characterized. These P-450 forms, designated as hamster P-450H and hamster P-450L, had the molecular masses of 52 and 50 kDa, respectively, and showed the absorption maximum of CO-reduced difference spectra at 446 nm. The absolute spectra of their oxidized forms indicated that hamster P-450H was in high-spin state and hamster P-450L was in low-spin state. A part of PenCDF injected into hamster was tightly bound to purified hamster P-450H at a ratio of 0.107 nmol PenCDF/nmol P-450. In a reconstituted system, both hamster P-450H and hamster P-450L showed relatively low catalytic activities for 3-hydroxylation of benzo[a]pyrene and O-deethylations of both 7-ethoxyresorufin and 7-ethoxycoumarin, while they both catalyzed 7 alpha- and 2 alpha-hydroxylations of testosterone effectively to a similar extent. Addition of cytochrome b5-to a reconstituted system accelerated the formation of 7 alpha-hydroxytestosterone 5.3-fold with hamster P-450L and 2.2-fold with hamster P-450H. In addition, hamster P-450H catalyzed estradiol 2-hydroxylation at a high rate but hamster P-450L did not.(ABSTRACT TRUNCATED AT 250 WORDS)
Koga
N
N
Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka.
Ariyoshi
N
N
Nakashima
H
H
Yoshimura
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D006224:Cricetinae; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification* / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism; D008297:Male; D008647:Mesocricetus; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D008969:Molecular Sequence Data
D001572:Benzofurans; D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System; C038890:2,3,4,7,8-pentachlorodibenzofuran