PROSTATE-SPECIFIC ORIGIN OF DIPEPTIDYLPEPTIDASE-IV (CD-26) IN HUMAN SEMINAL PLASMA

Purpose: A number of peptidases which can metabolize certain bioactive peptides and growth factors have been identified in seminal plasma. O ur goal in this study was to determine molecular properties and the ti ssue source(s) for one of these peptidases, dipeptidylpeptidase IV (DP P IV), in human seminal plasma. Materials and Methods: We measured the activities of DPP TV with the dipeptide glycylprolyl-p-nitroanalide a nd its molecular forms using immunoblotting of seminal plasmas of men who were vasectomized or with different sperm concentrations, and in p rostatic and seminal vesicle secretions of men undergoing prostatic su rgery. Results: DPP IV in seminal plasma of vasectomized men was a mem brane associated dimer comprised of subunits of approximately 110 kDa. Its activity did not differ in seminal plasmas of vasectomized, azoos permic, oligozoospermic and normozoospermic men indicating no correlat ion with the concentration of sperm originally present in the semen. T he DPP TV antigen (CD -26) and enzymic activity were present in prosta tic secretion, but absent from that of the seminal vesicles. These dat a indicate that the prostate gland is the primary source of DPP IV act ivity in seminal plasma. There was little variation in its activities in repeat seminal plasma samples from the same individual, and there w as no change in its activity with age to 50 years. Conclusions: DPP IV in seminal plasma was derived from the prostate gland and it may be u seful as a bioindicator of prostate function and/or disease with age i n men.