We have characterized and compared the substrate specificity of affinity-purified recombinant rat testes endopeptidase EC 184.108.40.206 (EP 24.15) with that reported for the isolated brain enzyme. Of the peptides tested, only bradykinin, dynorphin A1-8, and neurotensin were efficiently cleaved by the recombinant enzyme (kcat/Km = 3.0, 2.8 and 0.5 × 105 M-1sec-1, respectively); other peptides considered substrates of EP 24.15 (gonadotropin-releasing hormone, substance P, somatostatin and angiotensin) were not metabolized. The enzyme was inhibited by metal ion chelators and thiol-reactive agents, as well as a specific EP 24.15 inhibitor (N-[1(R, S)-carboxy-3-phenylpropyl]-Ala-Ala-Tyr-p-aminobenzoate), thus confirming the enzyme as a thiol-dependent metalloendopeptidase. The observed discrepancies in substrate specificity of the recombinant testicular and the isolated brain enzymes may result from tissue-specific forms and/or post-translational modifications of EP 24.15.
|Number of pages||8|
|Journal||Biochemical and Biophysical Research Communications|
|Publication status||Published - 26 Apr 1995|