Comparison of LHRH-peptidase and plasminogen activator activity in rat testis extracts.
Testicular LHRH-peptidase and testicular urokinase-type plasminogen activator are Sertoli cell-secreted proteases which display similar molecular properties. However, there is relatively little information regarding the substrate specificity and potential cross-reactivity of these enzymes. Testicular extracts were prepared from homogenates of whole rat testes and assessed by LHRH-peptidase assay, and by radial caseinolysis assays for plasminogen activator and plasmin-like activity. Following partial purification of the protease activities in testicular extracts by gel filtration and ion-exchange chromatography, it was confirmed that testicular LHRH-peptidase and plasminogen activator are clearly separable. There was no detectable plasmin-like activity in the testicular extracts; however, the extracts were found to contain an inhibitor, or inhibitors, of both plasminogen activator and plasmin activity. In addition to LHRH and Gly6-substituted LHRH analogues, the partially purified LHRH-peptidase degraded both angiotensins I and II, but not the gonadotrophin-releasing-hormone-associated peptide derived from the LHRH precursor molecule. These properties of the LHRH-peptidase provide further evidence that it is a testis-specific prolyl endopeptidase, involved in regulating and/or limiting peptide activity in the testis.
Hedger
M P
MP
Institute of Reproduction and Development, Monash University, Monash Medical Centre, Clayton, Vic., Australia. mark.hedger@med.monash.edu.au
Culler
M D
MD
D000818:Animals; D002364:Caseins / Q000378:metabolism; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D005341:Fibrinolysin / Q000378:metabolism; D006801:Humans; D008297:Male; D008666:Metalloendopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D013737:Testis / Q000201:enzymology*; D014568:Urokinase-Type Plasminogen Activator / Q000302:isolation & purification / Q000378:metabolism*
D002364:Caseins; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator; D008666:Metalloendopeptidases