Partial characterization of testosterone 5 alpha-reductase solubilized from rat testicular microsomes

Testosterone 5 alpha-reductase was successfully solubilized by the use of digitonin from rat testicular microsomes and then partially purified by polyethylene glycol fractionation and DEAE-Sephacel column chromatography. The 5 alpha-reductase activity of the partially purified preparation was significantly stimulated by addition of phosphatidylserine (bovine brain). Synthetic dilauroylphosphatidylcholine also increased the reductase activity to a somewhat lesser extent than did phosphatidylserine, whereas natural phosphatidylcholine from bovine liver did not exhibit any stimulation. When synthetic phosphatidylcholines with varying acyl chain lengths were tested for their stimulatory effects on the reductase activity, dilauroylphosphatidylcholine was most active; dimyristoylphosphatidylcholine was less active; dioleoylphosphatidylcholine was almost inactive.