title: Calcium-dependent proteinases and specific inhibitors: calpain and calpastatin.
abstract: There are two forms of Ca2+-dependent cysteine proteinase: low Ca2+ (microM concentration)-requiring calpain I and high Ca2+ (mM concentration)-requiring calpain II. We have recently succeeded in establishing an efficient method for isolating calpains I and II from several tissues and also a method for separating the heavy (80 kDa) and light (30 kDa) subunits from a calpain molecule. These methods enabled us to obtain a variety of calpains I and II and their subunit proteins each in a highly pure state so that these proteins can be compared physically, chemically and immunologically. Calpastatin, a calpain-specific endogenous inhibitor protein, was also purified and characterized. Although the intercellular localization of calpains I and II is being elucidated by use of the respective monospecific antibodies, the true biological functions of calpain and calpastatin still remain rather obscure.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000302:isolation & purification*; D002154:Calpain / Q000302:isolation & purification* / Q000502:physiology; D004912:Erythrocytes / Q000032:analysis; D006801:Humans; D007668:Kidney / Q000032:analysis; D008099:Liver / Q000032:analysis; D010446:Peptide Fragments / Q000302:isolation & purification; D011480:Protease Inhibitors / Q000302:isolation & purification*; D051381:Rats; D013379:Substrate Specificity; D013552:Swine
chemical_list: D002135:Calcium-Binding Proteins; D010446:Peptide Fragments; D011480:Protease Inhibitors; C033668:calpastatin; D002154:Calpain; D002118:Calcium