TY - JOUR
T1 - Immunochemical studies on the metabolism of nitrosamines by ethanol-inducible cytochrome P-450
AU - Yang, Chung S.
AU - Koop, Dennis R.
AU - Wang, Tianyuan
AU - Coon, Minor J.
N1 - Funding Information:
*This work was supported by Grant CA-37037 and AN-10339 from the NIP. *ro whom requests for reprints should be addressed. kn leave from Henan Tumor Institute, Zhengzhou, Henan, China demethylase; . .
PY - 1985/4/30
Y1 - 1985/4/30
N2 - The ethanol-induced rabbit liver microsomal cytochrome P-450, P-450LM3a, has been shown previously to efficiently catalyze the demethylation of N-nitrosodimethylamine (NDMA) with a Km of 2.9 mM. Since the predominant Km in hepatic microsomes from ethanol-treated rabbits is 0.07 mM, the role of P-450LM3a in the activation of this carcinogen has been uncertain. In the present study, antibodies to P-450LM3a were shown to almost completely inhibit NDMA demethylation by the purified P-450 in a reconstituted system as well as the low-Km activity of liver microsomes from control or ethanol-treated rabbits. In contrast, the antibody did not inhibit the high-Km NDMA demethylase activity in the microsomes. These results indicate that P-450LM3a is the major P-450 responsible for the low-Km NDMA demethylase activity. In addition, evidence is provided for the existence of a cytochrome immunochemically similar to P-450LM3a in liver microsomes from rats, mice, and guinea pigs that effectively catalyzes the demethylation of NDMA.
AB - The ethanol-induced rabbit liver microsomal cytochrome P-450, P-450LM3a, has been shown previously to efficiently catalyze the demethylation of N-nitrosodimethylamine (NDMA) with a Km of 2.9 mM. Since the predominant Km in hepatic microsomes from ethanol-treated rabbits is 0.07 mM, the role of P-450LM3a in the activation of this carcinogen has been uncertain. In the present study, antibodies to P-450LM3a were shown to almost completely inhibit NDMA demethylation by the purified P-450 in a reconstituted system as well as the low-Km activity of liver microsomes from control or ethanol-treated rabbits. In contrast, the antibody did not inhibit the high-Km NDMA demethylase activity in the microsomes. These results indicate that P-450LM3a is the major P-450 responsible for the low-Km NDMA demethylase activity. In addition, evidence is provided for the existence of a cytochrome immunochemically similar to P-450LM3a in liver microsomes from rats, mice, and guinea pigs that effectively catalyzes the demethylation of NDMA.
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U2 - 10.1016/0006-291X(85)90147-0
DO - 10.1016/0006-291X(85)90147-0
M3 - Article
C2 - 3994708
AN - SCOPUS:0021841154
VL - 128
SP - 1007
EP - 1013
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 2
ER -