Genetic variations of an oxidase in mammals.

The genetic basis of the variation in activity of the mammalian enzyme which catalyzes the oxidation of N1-methylnicotinamide to N1-methyl-4-pyridone-3-carboxamide has been investigated. The data indicate that in mice the magnitude of the enzyme activity depends on a pair of autosomal alleles, one of which determines a high level, the other a low level, of enzyme activity. Differences in enzyme activity between males and females and the effect of administration of estradiol and of testosterone to intact animals indicate that the level of enzyme activity is subject to hormonal influence as well. Thus, whereas the distinction between classes with low and high enzyme activity is under genetic control, levels of enzyme activity within these classes appear to be regulated by the endocrine system.