On the basis of their biological activity, corti-costeroids can be divided into two types, miner-alocorticoids and glucocorticoids. The mineralo-corticoid biosynthetic pathway, leading to the formation of aldosterone, involves three sequential hydroxylation reactions. First, progesterone is converted to two compounds with min-eralocorticoid activity, through the action of 21-hydroxylase and 11^-hydroxylase: 11-deoxy-corticosterone (DOC) and corticosterone, respectively. The latter compound has approximately 10 times more mineralocorticoid activity than DOC. Subsequently, corticosterone is transformed to 18-hydroxycorticosterone via 18-hydroxylase. This product then undergoes oxidation of the hydroxyl group at carbon 18 through the action of the enzyme aldehyde syn-thetase (18-oxidase), to form aldosterone. This mineralocorticoid is about 10 times more potent than corticosterone.
In contrast to the mineralocorticoid pathway, the glucocorticoid pathway, leading to formation of cortisol, begins with 17-hydroxyprogesterone. The latter compound is converted to 11-deoxy-cortisol, which is then transformed to cortisol through the action of 21-hydroxylase and 11jS-hydroxylase, respectively. These reactions are analagous to the formation of corticosterone from progesterone. Cortisol has high glucocor-ticoid activity, in contrast to 11-deoxycortisol, which lacks significant amounts of this activity.
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