Interaction between cytochrome P450 and other drug-metabolizing enzymes: Evidence for an association of CYP1A1 with microsomal epoxide hydrolase and UDP-glucuronosyltransferase

Protein-protein interactions between cytochrome P450 (P450) and other drug- metabolizing enzymes were studied by affinity chromatography using CYP1A1-, glycine-, and bovine serum albumin (BSA)-conjugated Sepharose 4B columns. Sodium cholate-solubilized microsomes from phenobarbital-treated rat liver were applied to the columns and the material eluted with buffer containing NaCl was analyzed by immunoblotting. Microsomal epoxide hydrolase (mEH) and UDP-glucuronosyltransferases (UGTs), as well as NADPH-P450 reductase, were efficiently trapped by the CYP1A1 column. Glycine and BSA columns exhibite d no ability to retain these proteins. Protein disulfide isomerase and caln exin, non-drug-metabolizing enzymes expressed in the endoplasmic reticulum, were unable to associate with the CYP1A1 column. These results suggest tha t CYP1A1 interacts with mEH and UGT to facilitate a series of multistep dru g metabolic conversions, (C) 2000 Academic Press.