• Prostate;
  • seminal plasma;
  • transglutaminase

PROBLEM: Initial studies from this laboratory of human seminal plasma (SePI) permitted the presumptive identification of the participation of transglutaminase (TGase) and prostaglandins as principal molecules contributing to the immunoregulatory activity of SePI. As a step toward confirmation and extension of these studies, SePI TGase has been partially purified, characterized, and localized.

METHOD OF STUDY: An enzyme-enriched and partially purified preparation of SePI TGase obtained by molecular sieve and ion-exchange chromatography and the polyclonal antibody to this preparation were characterized by enzymatic analysis and evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE); immunoprecipitation and immunofluorescence (IF).

RESULTS: A Ca2+ -dependent, thrombin-independent, TGase enzyme from SePI was identified. A pH of 7.5 and a concentration of 2 mM calcium chloride were determined to be optimal for ascertaining the SePI TGase activity in a filter paper assay. Immunoprecipitation using polyclonal antibody prepared with a semipurified TGase preparation, concurrently comparing increasing serum dilution and enzyme activity, revealed a predominant protein band on SDS-PAGE of 83 kDa. IF studies using the polyclonal antibody on human prostate tissue showed reactivity with a variety of epithelial and stromal components. A significant (P < 0.05) correlation between the biochemical, i.e., enzyme activity of the SePI TGase active preparation, and immunologic activity, i.e., indirect IF staining titre of antibody to acinar epithelial cells and luminal contents, was observed.

CONCLUSIONS: The results confirm and extend initial studies of the presumptive identification of a tissue type TGase associated with the immunoregulatory activity of human SePl and permit the characterization and immunohistologic localization of this macromolecule to the prostate. These observations provide a basis for further investigation of the immunoregulatory role of SePl and prostate TGase in the biology of reproduction and associated pathoses.