Partial purification of human prostatic 5 alpha-reductase (3-oxo-5 alpha-steroid:NADP+ 4-ene-oxido-reductase; EC 1.3.1.22) in a stable and active form.

Human hyperplastic prostate tissue was homogenised in high ionic strength buffer and the post nuclear homogenate was incubated with 0.8% octyl glucoside and bovine brain lipids. Dialysis of the resulting liposome suspension yielded a preparation in which 5 alpha-reductase was active and stable for at least three weeks and showed an increase in specific activity (Vmax +/- SD = 48.9 +/- 7.4 pmol DHT/mg protein/ml) over that of the starting homogenate (Vmax +/- SD = 5.6 +/- 1.5 pmol DHT/mg protein/min) of 8.7 times.