Partial characterization of testosterone-metabolizing enzymes in the quail brain

The properties of 5 beta-reductase, 5 alpha-reductase and aromatase, 3 testosterone metabolizing enzymes, were studied in the quail brain by an in vitro incubation technique. The results describe the changes in time of metabolite production and the effects of temperature, enzyme and cofactor concentrations. The apparent Km and Vmax were evaluated for the 3 enzymes. Aromatase and 5 alpha-reductase have a higher affinity but a lower capacity than 5 beta-reductase. The kinetics of the latter enzyme are complex and suggest the presence of two types of enzymes. These characteristics fit in well with the role probably played by the enzymes in vivo.