INTERACTION OF CYTOCHROME P450 AND MICROSOMAL EPOXIDE HYDROLASE AND UDP-GLUCURONOSYLTRANSFERASE

Abstract

Interaction between cytochrome P450 (P450) and other sorts of drug metabolizing enzymes was studied by affinity chromatography with CYP1A1-conjugated column. Solubilized rat liver microsomes were charged onto the column and the eluate was analyzed by immunoblotting. The result showed that the CYP1A1 column effectively trapped microsomal epoxide hydrolase (mEH) and UDP-glucuronosyltransferase (UGT) as well as NADPH-P450 reductase. Non-drug metabolizing enzymes such as calnexin and protein disulfide isomerase did not show any affinity to the column. Neither BSA- nor glycine-conjugated column could trap microsomal protein. These results strongly suggest the specific interaction between P450 and mEH/UGT. When estimated using stereo-selective hydrolysis for styrene oxide as the index, the function of rat mEH was enhanced by co-incubation with CYP1A1, 2B1 and 2C11. The same picture was also seen for the interaction between dog mEH and CYP2B11/3A12. These results suggest that P450 interacts with mEH and UGT to facilitate a series of multistep metabolic conversion.