Properties and biochemical characterization of NADH 5 alpha-reductase from rat liver microsomes.

NADH 5 alpha-reductase is present in microsomes of various rat organs: heart and skeletal muscle, liver, adrenal glands, kidney, testes and prostate. The enzyme from rat liver microsomes utilizes B-hydrogen from the coenzyme NADH for steroid reduction. After solubilization of the enzyme with the nonionic detergent lubrol, phosphatidylcholine is necessary to restore the activity. This reactivation of the enzyme activity is paralleled by a corresponding increase of Vmax for testosterone (17 beta-hydroxy-4-androsten-3-one). Km and Vmax for testosterone change, Km and Vmax for the coenzyme NADH remain constant with an alteration of phosphate concentration in the incubation medium. The NADH 5 alpha-reductase is inhibited by numerous substances: amytal, phenobarbital, mepacrin, thenoyltrifluoracetone, gallic acid propyl ester, dicoumarol, pentachlorophenol, NADP and antibodies against rat liver NADPH ferrihemoprotein reductase. Antibodies against rat liver cytochrome-b5 reductase cause an activation of NADH 5 alpha-reductase.