Substrate specificity differences between recombinant rat testes endopeptidase EC and the native brain enzyme

Rebecca A. Lew, Nina J. Hey, Timothy J. Tetaz, Marc J. Glucksman, James L. Roberts, A. Ian Smith

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We have characterized and compared the substrate specificity of affinity-purified recombinant rat testes endopeptidase EC (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.

Original languageEnglish
Pages (from-to)788-795
Number of pages8
JournalBiochemical and Biophysical Research Communications
Issue number3
Publication statusPublished - 26 Apr 1995
Externally publishedYes

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