CYP2A6 is a major hepatic member of the cytochrome P450 family in humans. Much variation in CYP2A6 levels and activity can be attributed to genetic polymorphisms of this gene. CYP2A6*25 comprises an amino acid substitution, F118L. To clarify the effect of the leucine substitution at position 118 in CYP2A6.25, this variant, wild type CYP2A6 and three additional variants consisting of artificial mutations at the substrate binding site (position 481) suggested by earlier reports using random mutagenesis studies [CYP2A6.1, CYP2A6.25, CYP2A6.1(F118A), CYP2A6.1(A481G) and CYP2A6.25(A481G)], were co-expressed with NADPH-cytochrome P450 reductase in E. coli. The hydroxylase activity of these variants toward 7-ethoxycoumarin, coumarin, flavone, α-naphthoflavone, flavanone and hydroxyflavanone were examined. All the mutants had lower activities for coumarin 7-hydroxylation than the wild type. All the mutants showed higher activities for flavone and α-naphthoflavone compared with CYP2A6.1. CYP2A6.1 had the highest flavanone 2'-hydroxylase activity, whereas CYP2A6.25 had the highest 6- and 4'-hydroxylase activities. CYP2A6.1(F118A), CYP2A6.1(A481G) and CYP2A6.25(A481G) had higher flavanone 3'-hydroxylase activities than CYP2A6.1 and CYP2A6.25. Furthermore, 4'-hydroxyflavanone was metabolized by CYP2A6.25. These results indicate that the CYP2A6.25 mutation confers new substrate specificity towards flavonoids.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.