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

Arch Biochem Biophys. 1985 Nov 1;242(2):557-62. doi: 10.1016/0003-9861(85)90243-7.


Porcine calpains (Ca2+-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 amidase-like 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 carboxyl-terminal 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 Ca2+ requirements. The specificity constants, kcat/Km, for substance P were found to be three to four orders of magnitude higher than those for the synthetic substrates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aminopeptidases*
  • Animals
  • Calpain / blood
  • Calpain / metabolism*
  • Erythrocytes / enzymology
  • Kidney / enzymology
  • Kinetics
  • Substance P / analogs & derivatives*
  • Substance P / metabolism*
  • Substrate Specificity
  • Swine


  • Substance P
  • Aminopeptidases
  • Calpain