コイおよびウサギ筋肉のカルパインIIの含量と酵素的性質の比較

抄録

Calpain II, which requires millimolar calcium concentration for its activity, was extracted and purified from carp and rabbit skeletal muscles by using successive chromatographies of DEAF-cellulose, Ultrogel AcA 34, 2nd DEAE-cellulose, and Sephacryl S-300. Each of the purified calpain migrated as a single band on SDS-polyacrylamide gel electrophoresis.
The molecular weight of carp and rabbit calpains was estimated to be 80, 000 and 74, 000, respectively by gel filtration and SDS-polyacrylamide gel electrophoresis. The caseinolytic activity of the purified calpain was 147.4 and 203.0 unit/mg at pH 7.0 for carp and rabbit calpains, respectively. It was thus supposed that calpin content was 83.4 unit in 100g of carp muscle, while 215 unit in rabbit muscle.
Although both calpains had similar Ca²⁺ requirement (50% activation at 0.6-1.0mM CaCl₂) and heat-stability, rabbit calpain appeared to be less negatively charged than carp calpain based on their elution profiles from a DEAE-cellulose column. The optimum pH was 7.0 for carp calpain, while 7.5 for rabbit calpain. Rabbit calpain activity reduced more markedly in the presence of higher concentration of NaCl or KCl.