title: Functional characterization of CYP2A13 polymorphisms.
abstract: CYP2A13 is an efficient catalyst of metabolic activation of the human carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). This study investigated the functional consequences of CYP2A13 polymorphisms that result in single amino acid substitutions. Five CYP2A13 variants, namely CYP2A13*2 (R257C), CYP2A13*5 (F453Y), CYP2A13*6 (R494C), CYP2A13*8 (D158E), and CYP2A13*9 (V323L), were expressed and evaluated for coumarin binding affinity, coumarin 7-hydroxylation, and -hydroxylation of (S)-NNN and NNK. In addition, the 133_134 Thr deletion variant, coded for by CYP2A13*3, was expressed but was not stable to the protein purification procedure. A 30-42% decrease in coumarin 7-hydroxylation catalytic efficiency was determined for R257C and D158E. No effect on coumarin binding or (S)-NNN metabolism was observed. Three variants, R257C, D158E, and V323L, had two- to threefold decreased catalytic efficiency for NNK -hydroxylation. CYP2A13 polymorphisms resulted in modest changes in coumarin 7-hydroxylation and NNK -hydroxylation activities in vitro. Although these changes are not likely to impact in vivo metabolism, these data should aid in the interpretation and design of future epidemiology studies.
authors.affiliation: Department of Biochemistry, Molecular Biology, & Biophysics, University of Minnesota Cancer Center, Minneapolis, MN 55455, USA. murph062@umn.edu
authors.forename: K E
authors.initials: KE
authors.lastname: Schlicht
authors.forename: N
authors.initials: N
authors.lastname: Michno
authors.forename: B D
authors.initials: BD
authors.lastname: Smith
authors.forename: E E
authors.initials: EE
authors.lastname: Scott
authors.forename: S E
authors.initials: SE
authors.lastname: Murphy
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D019943:Amino Acid Substitution; D001189:Aryl Hydrocarbon Hydroxylases / Q000737:chemistry* / Q000235:genetics*; D002273:Carcinogens / Q000737:chemistry* / Q000378:metabolism; D003374:Coumarins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006900:Hydroxylation; D009602:Nitrosamines / Q000737:chemistry* / Q000378:metabolism; D011110:Polymorphism, Genetic; D017384:Sequence Deletion
chemical_list: D002273:Carcinogens; D003374:Coumarins; D009602:Nitrosamines; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; C030123:coumarin; D001189:Aryl Hydrocarbon Hydroxylases; C414206:CYP2A13 protein, human; C008655:N'-nitrosonornicotine