Intracellular Ca2+-dependent protease (CALPAIN) and its high-molecular-weight endogenous inhibitor (CALPASTATIN)

Ca2+‐dependent association between a Ca2+‐activated neutral proteinase (CaANP) and its specific inhibitor

“…When we have purified CaANP from rabbit skeletal muscle, no calcium-stimulated proteolytic activity on casein could be detected in the crude extract but after sepuation from the inhibitor by ion-exchange chromatography, this activity was easily measured. The presence of a similar proteinase inhibitor was also demonstrated in various other tissues (brain, lung, heart, liver) [4][5][6]. The simultaneous presence of CaANP [5-lo] in these tissues seems to indicate that proteolysis by this enzyme may be closely controlled.…”

“…The simultaneous presence of CaANP [5-lo] in these tissues seems to indicate that proteolysis by this enzyme may be closely controlled. Ca2+ may play a role in the association between the enzyme and its specific inhibitor [3,5,11].…”

Amino acid sequence around the active site cysteine residue of calcium‐activated neutral protease (CANP)

“…Two minor fractions were detected as in fig.lA and C, but they were not characterized further. Amino acid analysis of the active site peptide indicated that it was composed of 7 amino acid residues: Asp 1.09 (l), Gly 1.04 (I), Ala 0.88 (l), Leu 0.99 (l), CmCys 0.67 (I), and Trp 1.75 (2). This composition showed that it was essentially pure, though small amounts (< 0.2) of Ser, Glu, Tyr and Phe were also detected.…”

“…Calcium-activated neutral protease (CANP, EC 3.4.22.17), a typical intracellular protease, is classified as a thiol protease from the effect of various inhibitors for thiol proteases [1,2]. However, direct evidence supporting this classification has not been reported and it is not clear whether CANP is related to thiol proteases or metal proteases.…”

Do hydrophobic sequences cleaved from cellular polypeptides induce membrane fusion reactions in vivo?

“…This indicates that the Cat+-activated cysteine proteinase is more important in these cells, and it is interesting that the content of calpastatin, an endogenous inhibitor of the Ca'+-activated, cysteine proteinase known as calpain I is extremely small in rat erythrocytes, whiIe in human erythrocytes there is much more inhibitor than enzyme [21]. A recent report has shown that the fusogenic action of PEG on mouse erythrocytes is similarly related to the activity of a Ca2+-activated cysteine proteinase in both normal red blood cells and with malaria-infected cells 1221.…”