title: Pyroglutamyl peptidase I and prolyl endopeptidase in human semen: increased activity in necrozoospermia.
abstract: Thyrotropin-releasing hormone (TRH) and its analogues have been reported to have important functions in human semen. In the present paper, we have characterized the activity of the TRH-degrading enzymes pyroglutamyl peptidase I and prolyl endopeptidase in the fluid and prostasomes of human semen and in subcellular fractions of the corresponding sperm. Enzymatic activities were measured fluorimetrically using beta-naphthylamine derivatives as substrate. Activity associated with both enzymes was detected in seminal fluid and in the prostasome fraction, as well as in soluble and particulate sperm subcellular fractions. Pyroglutamyl-peptidase I activity presented highest levels in the particulate sperm fraction, whereas the activity of prolyl endopeptidase was maximal in the soluble sperm fraction. In addition, we compared the activity of both enzymes in different seminal fractions in normozoospermic, fertile men and in subfertile patients with different abnormalities revealed by spermiogram analysis (astenozoospermia, necrozoospermia and teratozoospermia). The activities of pyroglutamyl peptidase I and prolyl endopeptidase in necrozoospermia were found to be higher in the corresponding soluble and particulate sperm fractions, respectively, with respect to those measured in normozoospermic semen. The results of the present study indicate that these enzymes may participate in regulating the levels of seminal TRH analogues and in mediating sperm death associated with necrozoospermia.
authors.affiliation: Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country, P.O. Box 699 Bilbao, Bizkaia, Spain. ofbvapaa@lg.ehu.es
authors.forename: Asier
authors.initials: A
authors.lastname: Valdivia
authors.forename: Jon
authors.initials: J
authors.lastname: Irazusta
authors.forename: David
authors.initials: D
authors.lastname: Fernández
authors.forename: Juan
authors.initials: J
authors.lastname: Múgica
authors.forename: Carmen
authors.initials: C
authors.lastname: Ochoa
authors.forename: Luis
authors.initials: L
authors.lastname: Casis
mesh_terms: D016923:Cell Death; D002458:Cell Fractionation; D004229:Dithiothreitol / Q000494:pharmacology; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D000085822:Prolyl Oligopeptidases; D011751:Pyroglutamyl-Peptidase I / Q000378:metabolism*; D012661:Semen / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D012697:Serine Endopeptidases / Q000378:metabolism*; D013094:Spermatozoa / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*
chemical_list: D007770:L-Lactate Dehydrogenase; D011751:Pyroglutamyl-Peptidase I; D012697:Serine Endopeptidases; C000705287:PREPL protein, human; D000085822:Prolyl Oligopeptidases; D004229:Dithiothreitol