Hydroxylation of 19-norandrostenedione by adrenal cortex mitochondrial P-450 11β

Abstract

The activity of purified bovine adrenocortical P-450 11β on the C 18-steroid, 4-estrene-3,17-dione (19-norandrostenedione), is described. The major steroid products were separated by HPLC and identified by GC-MS, and 1H- and 13C-NMR as 11β-, 18- and 6β-hydroxylated derivatives of 19-norandrostenedione. The turnover numbers of the 11β-, 18-and 6β-hydroxylase reactions were 45, 7.5 and 1.9 (mol/min/mol of P-450 11β), respectively, with a common K m of 44 μM. All of these activities required the presence of the electron donating system consisting of NADPH, adrenal ferredoxin (adrenodoxin) and its reductase. These findings provide additional insights into the versatile catalytic roles of P-450 11β in the adrenal cortex, in which it may act on C 18-19-nor-steroids in addition to its known activities on C 21 and C 19-steroids.