Effect of spermine on the inhibition by fatty acid on AMP deaminase reaction as a control system of the adenylate energy charge in yeast |
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Authors: | M Yoshino K Murakami |
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Affiliation: | Department of Biochemistry, New Jersey Medical School-CMDNJ, Newark, New Jersey 07103 USA |
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Abstract: | Treatment of rats with pyrazole elevated the hepatic microsomal dimethylnitrosamine demethylase activity (DMNd) by several fold. Methylethylnitrosamine demethylase activity was also increased by pyrazole, but some classical monooxygenase activities were not induced. The treatment induced a new protein species which has an apparent molecular weight of 52,000 dal and is believed to be a cytochrome P-450 isozyme. The involvement of a hemoprotein in the pyrazole-induced DMNd was demonstrated in an experiment with CoCl2 which decreased both the microsomal cytochrome P-450 content and DMNd. The induced enzyme with a single Km value of 0.061 mM and Vmax of 12.1 nmol/min/mg is probably the most efficient enzyme known to metabolize nitrosamines. NADPH-cytochrome P-450 reductase was also demonstrated to be an essential component enzyme of the DMNd. These results further substantiate the idea that the P-450-containing monooxygenase is responsible for the metabolism of dimethylnitrosamine in both the control and pyrazole induced microsomes. |
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Keywords: | DMN dimethylnitrosamine DMNd dimethylnitrosamine demethylase activity and P-450 cytochrome P-450 |
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