S. Imaoka et al., MUTAGENIC ACTIVATION OF 3-METHOXY-4-AMINOAZOBENZENE BY MOUSE RENAL CYTOCHROME-P450 CYP4B1 - CLONING AND CHARACTERIZATION OF MOUSE CYP4B1, Archives of biochemistry and biophysics, 321(1), 1995, pp. 255-262
A new P450 responsible for mutagenic activation of 3-methoxy-4-aminoaz
obenzene (3-MeO-AAB) which is a potent procarcinogen was purified from
renal microsomes of male mice using an index of umu gene expression.
The purified P450 had high bioactivation toward 3-MeO-AAB and also 2-a
minofluorene and 2-aminoanthracene. The antibody against this P450 com
pletely inhibited mutagenic activation of 3-MeO-AAB of mouse renal mic
rosomes. With immunoblotting, this form was present abundantly in rena
l microsomes of male mice but not in those of female mice, This P450 w
as also present in pulmonary microsomes of male and female mice but no
t in hepatic microsomes, The NH2-terminal amino acid sequence analysis
indicated that this form belonged to the CYP4B subfamily, Thus, mouse
kidney cDNA library was screened with rat CYP4B1 probe. The cDNA-dedu
ced amino acid sequence of isolated cDNA consisted of 511 amino acids
and bore 90, 86, and 84% similarities to rat, rabbit, and human CYP4B1
, respectively. The NH2-terminal amino acid sequence of the purified r
enal P450 and amino acid sequence of BrCN-digested peptides from the p
urified P450 agreed with the cDNA-deduced amino acid sequence, These r
esults suggest that CYP4B1 is a major form in renal microsomes of male
mice and plays a major role in mutagenic activation of 3-MeO-AAB. In
extrahepatic tissue, CYP4B1 may contribute to chemical carcinogenesis.
(C) 1995 Academic Press, Inc.