Functional characteristics of nuclear 5 alpha-reductase from rat ventral prostate.
The subcellular distribution and functional characteristics of 5 alpha-reductase (3-oxo-5 alpha-steroid: NADP+ 4-ene-oxidoreductase, EC 1.3.1.22) from rat ventral prostate were studied and compared to the 5 alpha-reductase from female rat liver. Tissue fractionation retained main enzymic activity in the microsomal fraction of rat liver, while 5 alpha-reductase from rat prostate was localized in the nuclear membrane with a specific activity 160 times that of the initial homogenate. The purity of nuclear envelopes was checked by electron microscopy. Solubilization experiments indicated that the hepatic 5 alpha-reductase is attached to the endoplasmic reticulum as a peripheral protein, while the nuclear prostatic enzyme is an integral membrane protein. Incubation experiments with phospholipases suggested a decisive role of the surrounding phospholipids for the prostatic enzyme activity. To elucidate the characteristics of hydrogen transfer of the enzyme, the effect of flavins and different other cofactors on 5 alpha-reductase activity in isolated prostatic nuclei were studied. Our findings indicate that in rat ventral prostate the conversion of testosterone to 5 alpha-dihydrotestosterone proceeds by a direct hydrogen transfer from NADPH to testosterone. Concerning these parameters the behaviour of hepatic 5 alpha-reductase is absolutely different from the prostatic enzyme. The localization of 5 alpha-reductase within the nuclear envelope of rat ventral prostate as an integral membrane protein seems to be of physiological significance with regard to the action of androgens.
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000032:analysis* / Q000302:isolation & purification; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D013196:Dihydrotestosterone / Q000096:biosynthesis; D004579:Electron Transport / Q000187:drug effects; D005260:Female; D008297:Male; D010740:Phospholipases / Q000494:pharmacology; D011467:Prostate / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility
D013196:Dihydrotestosterone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; D010740:Phospholipases