COMPARISON OF LHRH-PEPTIDASE AND PLASMINOGEN-ACTIVATOR ACTIVITY IN RAT TESTIS EXTRACTS

Testicular LHRH-peptidase and testicular urokinase-type plasminogen ac tivator are Sertoli cell-secreted proteases which display similar mole cular properties. However, there is relatively little information rega rding the substrate specificity and potential cross-reactivity of thes e enzymes. Testicular extracts were prepared from homogenates of whole rat testes and assessed by LHRH-peptidase assay, and by radial casein olysis assays for plasminogen activator and plasmin-like activity. Fol lowing partial purification of the protease activities in testicular e xtracts by gel filtration and ion-exchange chromatography, it was conf irmed that testicular LHRH-peptidase and plasminogen activator are cle arly separable. There was no detectable plasmin-like activity in the t esticular extracts; however, the extracts were found to contain an inh ibitor, or inhibitors, of both plasminogen activator and plasmin activ ity. In addition to LHRH and Gly(6)-substituted LHRH analogues, the pa rtially purified LHRH-peptidase degraded both angiotensins I and II, b ut not the gonadotrophin-releasing-hormone-associated peptide derived from the LHRH precursor molecule. These properties of the LHRH-peptida se provide further evidence that it is a testis-specific prolyl endope ptidase, involved in regulating and/or limiting peptide activity in th e testis.