title: Characterization of brain calpains.
abstract: A new, simple one-step procedure [Karlsson et al. Biochem. J. 231, 201-204 (1985)] for the separation of calpains I and II was used prior to the characterization of these enzymes from rabbit brain, using alkali-denatured casein as the substrate. Enzyme activity was dependent on Ca2+ ions and free-SH groups and was maximal around pH 7.4. Incubation of calpains I and II with Ca2+ in the absence of substrate led to a rapid loss of enzyme activity. Enzyme activity was linear at room temperature and millimolar Ca2+ concentrations. However, when incubation of calpain I was performed with micromolar Ca2+ concentrations at room temperature proteolytic activity exhibited a lag period of approximately 10 min. This activation period was not as evident with calpain II.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002413:Cations, Divalent; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D011480:Protease Inhibitors / Q000494:pharmacology; D011817:Rabbits; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013696:Temperature
chemical_list: D002413:Cations, Divalent; D011480:Protease Inhibitors; D013439:Sulfhydryl Reagents; D002154:Calpain; D002118:Calcium