Glutathione S-transferases in human prostate

A number of human prostatic tissue biopsies have been analyzed for glutathione S-transferase activity, using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate. Samples from nine patients (age range 61-90) with benign prostatic hypertrophy who had received no prior chemotherapy had a mean glutathione S-transferase activity of 137 +/- 44 nmol/min per mg with a range of 97-237. A qualitative comparison of the glutathione S-transferase of normal prostate and benign prostatic hypertrophy samples was carried out. Approximately 260-fold purification was achieved using glutathione-Sepharose affinity chromatography, with glutathione S-transferase accounting for approximately 0.19-0.33% of the total protein. Substrate specificity determinations suggested similar, but not identical, glutathione S-transferase subunits in normal prostate and benign prostatic hypertrophy. One- and two-dimensional electrophoresis (isoelectric focusing and 12.5% SDS-polyacrylamide gel electrophoresis) identified at least seven stained polypeptides in the purified glutathione S-transferase preparations. These ranged in Mr from approximately 24,000 to 28,500 and in pI from near neutral to basic. Western blot analysis using polyclonal antibodies raised against rat liver glutathione S-transferase suggested crossreactivity with five of the human isoenzymes in both normal prostate and benign prostatic hypertrophy. One of the glutathione S-transferases, present in both normal prostate and benign prostatic hypertrophy, had an Mr of approx. 24,000 and a near-neutral pI and crossreacted immunologically with a polyclonal antibody raised against human placental glutathione S-transferase (Yf, subunit 7 or pi). These data suggest that four glutathione S-transferases are expressed in human prostate, with subunits from each of the major classes alpha, mu and pi. These are characterized as Ya, Yb, Yb' and Yf (analogous alternative nomenclature subunits 1, 3, 4 and 7).