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

Molecular Carcinogenesis - Tập 2 Số 4 - Trang 192-198 - 1989
Toshifumi Aoyama1, Frank J. Gonzalez1, Harry V. Gelboin1
1Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland

Tóm tắt

AbstractThe vaccinia virus cDNA expression system was used to produce human cytochrome P450 IA2 in a hepatoma cell line that is devoid of significant basal levels of P450. The expressed enzyme yielded a reduced carbon monoxide‐bound difference spectrum with a λmax 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 to catalyze efficiently the p‐hydroxylation of aniline. Mouse IA2 also catalyzed ethoxyresorufin O‐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‐ to sevenfold more active than the human enzyme for activation of the procarcinogens 2‐acetylaminofluorene and benzo[a]pyrene‐trans‐7,8‐dihydrodiol and the promutagens Glu‐P‐2 and Trp‐P‐1. Comparable activities were observed with 2‐aminoanthracene, 2‐aminofluorene, and Glu‐P‐1. These data demonstrate the utility of cDNA expression for examining the activities of human P450s and further suggest potentially important differences in catalytic activities of orthologous P450s found in different species.

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