Amidase-like activity of calpain I and calpain II on substance P and its related peptides.
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.
Hatanaka
M
M
Sasaki
T
T
Kikuchi
T
T
Murachi
T
T
D000595:Amino Acid Sequence; D000626:Aminopeptidases; D000818:Animals; D002154:Calpain / Q000097:blood / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D013373:Substance P / Q000031:analogs & derivatives* / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine
D013373:Substance P; D000626:Aminopeptidases; D002154:Calpain