Nitrile hydratase from Rhodococcus erythropolis: Metabolization of steroidal compounds with a nitrile group

The progestin dienogest (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4,9-die n-3-one) was metabolized by the nitrile hydratase-containing microorganism Rhodococcus erythropolis. An enzymatic hydrolysis of the nitrile group at t he 17 alpha-side chain was intended to obtain novel derivatives and to test them for progesterone receptor affinity. In contrast to the rapid enzymati c hydrolysis of nonsteroidal nitriles, the nitrile group of dienogest was c leaved very slowly. The dominant reaction was an aromatization of ring A. A fter prolonged fermentation, the 17 alpha-acetamido derivatives of estradio l and of 9(11)-dehydroestradiol were formed. Three of the metabolites were also prepared synthetically. They were tested for hormonal activity by asse ssing their binding to progesterone and estrogen receptors in vitro. Neithe r the aromatized 17 alpha-acetamido derivatives nor the dienogest derivativ e 17 alpha-acetamido-17 beta-hydroxy-estra-4,9-dien-3-one, which was prepar ed synthetically only, exhibited affinity for the progesterone receptor. (C ) 1999 Elsevier Science Inc. All fights reserved.