title: Roles of NADPH-P450 reductase in the O-deethylation of 7-ethoxycoumarin by recombinant human cytochrome P450 1B1 variants in Escherichia coli.
abstract: Four human cytochrome P450 1B1 (CYP1B1) allelic variants were purified from membranes of Escherichia coli in which respective CYP1B1 cDNAs and human NADPH-P450 reductase cDNA have been introduced. Purified CYP1B1 variants were used to reconstitute 7-ethoxycoumarin O-deethylation activities with purified rabbit liver or recombinant (rat) NADPH-P450 reductase in the phospholipid vesicles and compared with those catalyzed by CYP1B1 enzymes in the membranes of E. coli in monocistronic (by adding the reductase) and bicistronic (without addition of extra reductase) systems. In the bicistronic system, the ratio of expression of NADPH-P450 reductase to CYP1B1 proteins was found to range from 0.2 to 0.5. Purified CYP1B1 enzymes (under optimal reconstitution conditions) catalyzed 7-ethoxycoumarin O-deethylation at rates one-third to one-fourth of those catalyzed by membranes of E. coli coexpressing CYP1B1 and the reductase proteins. Full catalytic activities in reconstituted systems were achieved with a twofold molar excess of NADPH-P450 reductase to CYP1B1; in membranes of E. coli with the monocistronic CYP1B1 construct, an eightfold molar excess of reductase to CYP1B1 was required. However, in membranes of bicistronic constructs, there was no additional stimulation of 7-ethoxycoumarin O-deethylation by extra NADPH-P450 reductase, despite the fact that the molar ratio of expression levels of reductase to CYP1B1 was <0.5. These results suggest that NADPH-P450 reductase produced in the bacterial membranes is more active in interacting with CYP1B1 proteins in the bicistronic system than the reductase added to artificial phospholipid vesicles or bacterial membranes.
authors.affiliation: Osaka Prefectural Institute of Public Health, 3-69 Nakamichi 1-chome, Higashinari-ku, Osaka, 537-0025, Japan. shimada@iph.pref.osaka.jp
authors.forename: T
authors.initials: T
authors.lastname: Shimada
authors.forename: F
authors.initials: F
authors.lastname: Tsumura
authors.forename: E M
authors.initials: EM
authors.lastname: Gillam
authors.forename: F P
authors.initials: FP
authors.lastname: Guengerich
authors.forename: K
authors.initials: K
authors.lastname: Inoue
mesh_terms: D000478:Alkylation; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002853:Chromatography, Liquid; D003374:Coumarins / Q000378:metabolism*; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D003374:Coumarins; D005656:Fungal Proteins; D011994:Recombinant Proteins; C017299:7-ethoxycoumarin; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585499:Cyp1b1 protein, rat; D065633:Cytochrome P-450 CYP1B1; D009247:NADH, NADPH Oxidoreductases; C408906:cytochrome P450 reductase, Aspergillus niger