A kinetic analysis of the 5α-reductases from human prostate and liver

Article abstract of DOI:10.1016/0039-128X(87)90010-9

A kinetic analysis of the 5α-reductases from human liver and prostate is presented. Human prostatic 5α-reductase follows an ordered sequential mechanism in which NADPh binds first followed by testosterone. The order of release of products is DHT followed by NADP⁺. The apparent K(m) of prostatic 5α-reductase for testosterone is 0.0339 ± 0.006μM, while the apparent K(m) for NADPh is 2.52 ± 0.65μM. Human liver 5α-reductase also follows a sequential mechanism. The apparent K(m) of the liver enzyme is 0.110 ± 0.08μM; the apparent K(m) for NADPH is 6.2 ± 0.6μM. The fact that both the liver and prostatic 5α-reductases have a sequential kinetic mechanism rules out the possibility that the reduction of testosterone to dihydrotestosterone involves an electron transport system as previously proposed.