METABOLISM AND METABOLIC ACTIVATION OF FOOD-COMPOSITION BY HUMAN P450 VARIANTS REPRESENTING SINGLE NUCLEOTIDE POLYMORPHISMS

[Purpose] Natural food-composition such as furanocoumarin 5-methoxypsoralen (5-MOP) and methyleugenol, contained in plants, are suggested to have cytotoxic or mutagenic properties. Human Cytochrome P450 subfamily is a candidate to convert natural compounds in foods into reactive intermediates. This study aimed to identify metabolites of 5-MOP and methyleugenol by CYP2A13 and CYP1A1. Furthermore, we want to clarify functional differences among CYP2A13 and CYP1A1 variants representing single nucleotide polymorphisms (SNPs). [Methods] Membrane fractions were prepared from E. coli expressing CYP2A13 variants (CYP2A13-1 (wild type), 4 (R101Q), 5 (F453Y), 6 (R494C), 8 (D158E) and 9 (V323L)) and CYP1A1 variants. These membrane fractions were incubated with 5-MOP and methyleugenol, and the metabolites of 5-MOP and methyleugenol were analyzed by HPLC. [Results and Discussion] All CYP2A13 and CYP1A1 variants were successfully expressed in E. coli system, and the contents of CYP2A13 polypeptides were about 5% of total protein. CYP2A13-1 converted 5-MOP into 5-MOP dihydrodiol, Km and Vmax values of the reaction were 1.44 micro M and 4.23 nmol/min/nmol P450, respectively. The generation of dihydrodiol implies the production of reactive intermediates in the converting process. Though most variants of CYP2A13 had similar catalytic activity of 5-MOP, the activity of CYP2A13-4 was not detectable. [Conclusion] This study suggests that the CYP2A13 enzyme is involved in the toxicity of 5-MOP and that the SNPs within CYP2A13, except for allele CYP2A13-4, have little effect on the severity of toxicity.