Enzymes involved in corticosteroid biosynthesis

A great deal of information is now available about the properties, constitution and clinical manifestations of deficiencies of the hydroxylases involved in corticosteroid synthesis [42,52,53], and only a fraction of that information can be mentioned here. All the hydroxylases are mixed-function oxidases, requiring NADPH and 02, and some seem to be associated with cyts P-450, viz. cyt P-450 u/3, cyt P-4502i, cyt P-45018. The following equation represents the reaction catalysed  

A similar conclusion has been drawn by New and Levine [53] and may help to explain the known clinical features of the 21-hydroxylase defect of congenital adrenal hyperplasia, i.e., the existence of the simple virilizing form and the salt-losing type. It has been suggested that the 21-hydroxylase activity is impaired in the ZF for both 17-hydroxy- and 17-deoxycorticosteroid pathways, so that 11-deoxycorti-sol levels (and also cortisol levels) are decreased (Fig. 7), and the build-up of excess 

There are also distinct possibilities that at least two forms of the adrenal mitochondrial 11/3-hydroxylase may exist, one in the ZG, involved in the conversion of DOC into aldosterone (Fig. 6) and another in the ZF/ZR, concerned with the conversion of DOC to cortisol and 4-androstenedione to ll/3-hydroxy-4-androstenedione. An alternative possibility is that several cyts P-450Uj3 may exist, which catalyse the 11/3-hydroxylation of DOC, 11-deoxycortisol and 4-androstenedione [60,61]. To make 

---