Abstract
Summary
In this study we have compared some properties of the microsomal and mitochondrial 3β-hydroxysteroid dehydrogenase/isomerase (HSD) from the rat adrenal cortex. The following major differences were noted: (i) the microsomal enzyme required exogenous NAD while the mitochondrial enzyme was active in the absence of added NAD. (ii) The mitochondrial enzyme was inhibited by a combination of rotenone, KCN, and citric acid cycle substrates. These agents did not influence the activity of the microsomal enzyme, (iii) The ratio of the specific activities of HSD to the 21-hydroxylase (a microsomal marker enzyme) was greater in the mitochondria than in the microsomes. We conclude that HSD is present in the inner mitochondrial membrane and, therefore, that the enzyme has a dual mitochondrial and microsomal localization in the rat adrenal cortex.
The authors wish to thank Drs. P. J. Mulrow and S. Y. Tan for several helpful discussions during the course of this study.
Get full access to this article
View all access options for this article.