| Abstract
| - Nardilysin (N-arginine dibasic convertase, EC 3.4.24.61) was first identified on the basis ofits ability to cleave peptides containing an arginine dibasic pair, i.e., Arg−Arg or Arg−Lys. However, itwas observed that an aromatic residue adjacent to the dibasic pair (i.e., Phe−Arg−Lys) could alter thecleavage site. In this study we determined whether nardilysin can cleave peptides at a single basic residue.Nardilysin cleaves β-endorphin at the monobasic site, Phe17−Lys18, with a kcat/Km of 2 × 108 M-1 min-1.This can be compared to a kcat/Km of 8.5 × 108 M-1 min-1 for cleavage between a dibasic pair in dynorphinB-13. Nardilysin also cleaves calcitonin at His−Arg and somatostatin-14 at Cys−Lys. We examined thehydrolysis of fluorogenic peptides based on the β-endorphin 12−24 sequence, Abz-T-P-L-V-T-L-X1-X2-N-A-I-I-K-Q-EDDnp. Nardilysin hydrolyzes the peptides when X1−X2 = F−K, F−R, W−K, M−K,Y−K, and L−K. The kinetics of cleavage at F−K and F−R are similar; however, K−F is not hydrolyzed.Nardilysin cleaves at two monobasic sites M−K and F−R of the kallidin model peptide Abz-MISLMKRPPGFSPFRSSRI-NH2, releasing desArg10 kallidin (KRPPGFSPF). However, nardilysin doesnot release desArg10 kallidin from the physiological precursor low molecular weight kininogen. Thesestudies extend the range of potential substrates for nardilysin and further substantiate that nardilysin is atrue peptidase.
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