Rat steroid 5α-reductase kinetic characteristics: Extreme pH-dependency of the type II isozyme in prostate and epididymis homogenates

In the 1995 study, researchers found that the activity of rat steroid 5α-reductase type II isozyme in prostate and epididymis homogenates was highly pH-dependent. The optimal pH for the enzyme varied with substrate concentration, with pH 5.0 being optimal at high substrate concentrations and pH 5.5 at lower concentrations. The maximum efficiency (Vmax/Km) occurred at pH 5.5 for both tissues. The study highlighted that the enzyme's activity is non-linear at acidic pH unless the homogenate is pre-adjusted to the desired pH, and that the discrepancies in literature regarding 5α-reductase characteristics could be due to variations in pH during assays. The extreme pH-dependency of the type II isozyme's kinetic characteristics could explain the variations in reported enzyme activity.