title: Six novel nonsynonymous CYP1A2 gene polymorphisms: catalytic activities of the naturally occurring variant enzymes.
abstract: Six novel nonsynonymous nucleotide alterations were found in the cytochrome P450 1A2 gene in a Japanese population, which resulted in the following amino acid substitutions: T83M, E168Q, F186L, S212C, G299A, and T438I. These individuals were heterozygous for the amino acid substitutions. The potential functional alterations caused by the amino acid substitutions were characterized by a cDNA-mediated expression system using Chinese hamster V79 cells. Among the six CYP1A2 variants, F186L showed the most profound and statistically significant reduction in O-deethylation of phenacetin and 7-ethoxyresorufin. Kinetic analyses performed for the ethoxyresorufin O-deethylation revealed that the Vmax of the F186L variant was approximately 5% of that of the CYP1A2 wild type, despite a 5-fold lower Km value of the variant, the consequence of which was reduced enzymatic activity toward the substrate. Thus, for the first time, phenylalanine at residue 186 is suggested to be a critical amino acid for catalytic activity.
authors.affiliation: Project Team for Pharmacogenetics, National Institute of Health Sciences, Tokyo, Japan.
authors.forename: Norie
authors.initials: N
authors.lastname: Murayama
authors.forename: Akiko
authors.initials: A
authors.lastname: Soyama
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Saito
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Kazuo
authors.initials: K
authors.lastname: Komamura
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Ueno
authors.forename: Shiro
authors.initials: S
authors.lastname: Kamakura
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kitakaze
authors.forename: Hideo
authors.initials: H
authors.lastname: Kimura
authors.forename: Yu-ichi
authors.initials: Y
authors.lastname: Goto
authors.forename: Osamu
authors.initials: O
authors.lastname: Saitoh
authors.forename: Masaaki
authors.initials: M
authors.lastname: Katoh
authors.forename: Teiichi
authors.initials: T
authors.lastname: Ohnuma
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Kawai
authors.forename: Kenji
authors.initials: K
authors.lastname: Sugai
authors.forename: Taisuke
authors.initials: T
authors.lastname: Ohtsuki
authors.forename: Chieko
authors.initials: C
authors.lastname: Suzuki
authors.forename: Narihiro
authors.initials: N
authors.lastname: Minami
authors.forename: Shogo
authors.initials: S
authors.lastname: Ozawa
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Sawada
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D006224:Cricetinae; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010078:Oxazines / Q000378:metabolism; D010615:Phenacetin / Q000378:metabolism; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D010078:Oxazines; C007649:ethoxyresorufin; D019388:Cytochrome P-450 CYP1A2; D010615:Phenacetin