ENZYMATIC CONVERSION OF DIHYDROTESTOSTERONE FROM 3-KETO TO 3-ENOL FORM IN THE RAT PROSTATE

Dihydrotestosterone (DHT) is the active androgen, as well as a strong tumor promoter in the prostate, where several enzymes are essential fo r the regulation of its activity. We localized four enzymes promoting the enolization of the 3-keto group of DHT in rat prostate. The enzyme s were purified by ion-exchange chromatography, acetone fractionation and gel filtration to homogeneity, and found to have molecular sizes o f 19.5, 22.0, 44.5 and 21.5 kDa. A partial characterization of the fou r enzymes revealed that their structure consisted of a common chain of 14.5 kDa with various subunits which differentiate the four enzymes f rom each other. All the enzymes exerted their activity only on 5-dihyd ro 3-keto steroids. The total enzymatic activity was strongly influenc ed by animal age, being very low before sexual maturation, as well as after castration. In the latter case the level of total activity fell to about 8% of control animals. Activity was also estimated in human, pork, ram and bovine prostate and it was found that all these species have 20 - 25 times lower enzyme levels than rat. These results, in com bination with the practically exclusive localization of the enzymes in the prostate, suggest a role relating to the bioavailability of DHT i n this gland.