Aromatase and nonaromatizing 10-demethylase activity of adrenal cortex mitochondrial P-45011β

Abstract 19-Oxoandrostenedione, the product of 19-hydroxyandrostenedione by the 19-oxidase activity of the purified P -450 11 β system of adrenal cortex mitochondria, was further oxidized and demethylated at the 10-position to give the C 18 -steroids, estrone (aromatase reaction) and 19-norandrostenedione (nonaromatizing 10-demethylase or C10–19 lyase reaction). These reactions, together with the initial hydroxylation of androstenedione at C19, form a sequence of P -450 11β -catalyzed C 19 -steroid 19-monooxygenase reactions. P -450 11 β is thus similar to placental endoplasmic P -450 AROM in some of its substrate specificity, but the two forms of P -450 appear to be different in both physiology and properties.