TY - JOUR
T1 - Molecular basis for a functionally unique cytochrome P450IIB1 variant
AU - Kedzie, K. M.
AU - Balfour, C. A.
AU - Escobar, G. Y.
AU - Grimm, S. W.
AU - He, Y. A.
AU - Pepperl, D. J.
AU - Regan, J. W.
AU - Stevens, J. C.
AU - Halpert, J. R.
PY - 1991
Y1 - 1991
N2 - Liver microsomes from phenobarbital-treated rats of four inbred strains expressing distinct allelic variants of cytochrome P450IIB1 were analyzed. The Wistar Munich (WM) strain exhibited 5- to 10-fold lower androstenedione 16β-hydroxylase activity (a specific P450IIB1 marker) than the Lewis, Wistar Kyoto, and Wistar Furth strains. The androstenedione 16β-hydroxylase in the WM liver microsomes was refractory to inactivation by N-(2-p-nitrophenethyl)chlorofluoroacetamide, a selective P450IIB1 inactivator in the other three strains. Purified P450IIB1-WM was insensitive to the inactivator and exhibited 5-fold lower androstenedione 16β-hydroxylase, testosterone 16-hydroxylase, and 7-ethoxycoumarin deethylase activities but the same benzphetamine demethylase activity and slightly higher androstenedione 16α-hydroxylase activity than a P450IIB1 purified from outbred Sprague-Dawley rats, which appears to correspond to the form in Lewis rats. The stereoselectivity of androstenedione 16-hydroxylation catalyzed by P450IIB1-WM (16β-OH:16α-OH = 1.4) is thus distinct from that (16β-OH:16α-OH = 12-15) of other P450IIB1 preparations described. A cDNA encoding P450IIB1-WM was cloned and sequenced, revealing a single amino acid substitution (Gly-478 → Ala) compared with the published sequence (Fujii-Kuriyama, Y., Mizukami, Y., Kawajiri, K., Sogawa, K., and Muramatsu, M. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 2793-2797). Heterologous expression of P450IIB1 and P450IIB1-WM confirmed the striking difference in androstenedione metabolite profiles, strongly implicating the involvement of Ala-478 in defining the distinctive catalytic properties of P450IIB1-WM.
AB - Liver microsomes from phenobarbital-treated rats of four inbred strains expressing distinct allelic variants of cytochrome P450IIB1 were analyzed. The Wistar Munich (WM) strain exhibited 5- to 10-fold lower androstenedione 16β-hydroxylase activity (a specific P450IIB1 marker) than the Lewis, Wistar Kyoto, and Wistar Furth strains. The androstenedione 16β-hydroxylase in the WM liver microsomes was refractory to inactivation by N-(2-p-nitrophenethyl)chlorofluoroacetamide, a selective P450IIB1 inactivator in the other three strains. Purified P450IIB1-WM was insensitive to the inactivator and exhibited 5-fold lower androstenedione 16β-hydroxylase, testosterone 16-hydroxylase, and 7-ethoxycoumarin deethylase activities but the same benzphetamine demethylase activity and slightly higher androstenedione 16α-hydroxylase activity than a P450IIB1 purified from outbred Sprague-Dawley rats, which appears to correspond to the form in Lewis rats. The stereoselectivity of androstenedione 16-hydroxylation catalyzed by P450IIB1-WM (16β-OH:16α-OH = 1.4) is thus distinct from that (16β-OH:16α-OH = 12-15) of other P450IIB1 preparations described. A cDNA encoding P450IIB1-WM was cloned and sequenced, revealing a single amino acid substitution (Gly-478 → Ala) compared with the published sequence (Fujii-Kuriyama, Y., Mizukami, Y., Kawajiri, K., Sogawa, K., and Muramatsu, M. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 2793-2797). Heterologous expression of P450IIB1 and P450IIB1-WM confirmed the striking difference in androstenedione metabolite profiles, strongly implicating the involvement of Ala-478 in defining the distinctive catalytic properties of P450IIB1-WM.
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M3 - Article
C2 - 1718996
AN - SCOPUS:0025721160
SN - 0021-9258
VL - 266
SP - 22515
EP - 22521
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 33
ER -