Isolation and characterization of a new cDNA clone belonging to the cytochrome P450 2C gene subfamily in hamsters.
Cytochrome P450s are heme-containing proteins which evolved from an ancestral gene to form a large superfamily of enzymes. We previously isolated three distinct CYP2C cDNAs, namely CYP2C25, 2C26, and 2C27, from liver cDNA libraries of male and female Syrian hamsters. In the present study, we isolated another cDNA clone, assigned as CYP2C28, from the same male cDNA library. This cDNA consisted of 1556 nucleotides and encoded a polypeptide of 490 amino acids. CYP2C28 showed relatively low identities to other hamster CYP2C forms (71.4-72.6% in amino acid sequences) and showed the highest similarity to rat CYP2C24 (88.7%), while the other hamster CYP2C forms showed high similarities among themselves (> 90.2%). CYP2C28 protein expressed in yeast catalyzed the N-demethylation of aminopyrine and benzphetamine, but did not catalyze the hydroxylation of tolbutamide, testosterone, and progesterone. Northern blot analysis demonstrated that CYP2C28 mRNA was expressed in hamster livers 1 week after birth, when the other hamster CYP2C forms were not detectable. The level of CYP2C28 mRNA increased to 3 weeks and then decreased with time in males. The level in females was lower than that in males. In adult hamsters, CYP2C28 was induced almost threefold by administration of phenobarbital but not affected by 3-methycholanthrene. On the other hand, administration of pregnenolone 16 alpha-carbonitrile induced CYP2C28 in females but not in males. These results indicate that CYP2C28 is a unique form in the hamster CYP2C subfamily.
Sakuma
T
T
Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Yokoi
T
T
Kamataki
T
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D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D003001:Cloning, Molecular; D006224:Cricetinae; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D008297:Male; D008647:Mesocricetus; D008969:Molecular Sequence Data; D005810:Multigene Family; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics*
D018076:DNA, Complementary; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C093818:CYP2C28 protein, Mesocricetus auratus; D039181:Steroid 16-alpha-Hydroxylase