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Amidase-like activity of calpain I and calpain II on substance P and its related peptides

Authors
Journal
Archives of Biochemistry and Biophysics
0003-9861
Publisher
Elsevier
Publication Date
Volume
242
Issue
2
Identifiers
DOI: 10.1016/0003-9861(85)90243-7
Keywords
  • Protein Structure And Function
Disciplines
  • Biology

Abstract

Abstract Porcine calpains (Ca 2+-dependent cysteine proteinases) I and II, which had been purified each to a homogeneous state, were found to hydrolyze specifically carboxyl-terminal amide of substance P and several other biologically active peptidyl amides. This amidaselike activity was demonstrated both by determining released ammonia and by separating products on high-performance liquid chromatography followed by amino acid analysis. The calpain-catalyzed deamidation of substance P occurred exclusively at the carboxylterminal amide, leaving the side-chain glutamine intact. Enkepharinamide and MSH-release inhibiting factor were scarcely deamidated. Calpains I and II showed similar specificities for these amide substances and similar profiles of inhibitions by various protease inhibitors, but distinctly different Ca 2+ requirements. The specificity constants, k cat K m , for substance P were found to be three to four orders of magnitude higher than those for the synthetic substrates.

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