title: Calpain and calpastatin in porcine retina. Identification and action on microtubule-associated proteins.
abstract: Two forms of Ca2+-dependent cysteine proteinase (calpain, EC 3.4.22.17) and their specific endogenous inhibitor (calpastatin) were partially purified from porcine retina: calpain I (low-Ca2+-requiring form) was half-maximally activated at 8 microM-Ca2+, and calpain II (high-Ca2+-requiring form) at 250 microM-Ca2+. Both calpain I and calpain II were inhibited by calpastatin. Calpain I from porcine retina was shown to be composed of 83 000- and 29 000-Mr subunits, and calpain II of 80 000- and 29 000-Mr subunits, by the use of monospecific antibodies. Calpains I and II were both found to hydrolyse microtubule-associated proteins 1 and 2 rapidly.
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000302:isolation & purification; D002154:Calpain; D002848:Chromatography, DEAE-Cellulose; D010450:Endopeptidases / Q000302:isolation & purification / Q000494:pharmacology; D007122:Immunoelectrophoresis; D007527:Isoenzymes / Q000302:isolation & purification / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects; D011480:Protease Inhibitors / Q000302:isolation & purification; D012160:Retina / Q000201:enzymology*; D013552:Swine
chemical_list: D002135:Calcium-Binding Proteins; D007527:Isoenzymes; D011480:Protease Inhibitors; C033668:calpastatin; D010450:Endopeptidases; D002154:Calpain