Human cDNA-Expressed Cytochrome P450 IA2: Mutagen Activation and Substrate Specificity

✍ Scribed by Toshifumi Aoyama; Frank J. Gonzalez; Harry V. Gelboin

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 615 KB
• Volume: 2
• Category: Article
• ISSN: 0899-1987
• DOI: 10.1002/mc.2940020405

✦ Synopsis

The vaccinia virus cDNA expression system was used t o produce human cytochrome P450 IA2 in a hepatoma cell line that is devoid o f significant basal levels o f P450. The expressed enzyme yielded a reduced carbon monoxide-bound difference spectrum with a A , , , of 449 nm. Catalytic activities and mutagen activation ability of the human enzyme were assessed and directly compared with results obtained with the orthologous mouse IA2, which was also expressed using vaccinia virus. Both the human and mouse enzymes were able t o catalyze efficiently the phydroxylation o f aniline. Mouse IA2 also catalyzed ethoxyresorufin 0-deethylation, and its activity was sevenfold greater than expressed human IA2. The mouse and human enzymes also activated several promutagens and procarcinogens. Mouse IA2 was five-t o sevenfold more active than the human enzyme for activation o f the procarcinogens 2-acetylaminofluorene and benzo[a]pyrene-trans-7,8-dihydrodiol and the promutagens Glu-P-2 and Trp-P-l . Comparable activities were observed with 2-aminoanthracene, 2-aminofluorene, and GIu-P-1. These data demonstrate the utility o f cDNA expression for examining the activities of human P450s and further suggest potentially important differences in catalytic activities o f orthologous P450s found in different species.