Comparison of the properties of m-calpain from tilapia and grass shrimp muscles

m-Calpains from tilapia and grass shrimp muscles were purified by Phenyl-Sepharose CL-4B, Sephacryl S-200, Q-sepharose HP, and Superose 12 HR column chromatographies. The calpains from tilapia and grass shrimp muscles had the following characteristics: half-maximal activation, 0.23 and 2.4 mM of calcium; optimal temperature, 30 and 30 degrees C; optimal pH, 7.5 and 6.9; molecular weight: 110 000 and 160 000, respectively. m-Calpain obtained from tilapia muscle had two subunits of 80 000 and 28 000, while that from grass shrimp had two identical subunits of 80 000. Both proteases were activated by dithiothreitol, glutathione, and beta-mercaptoethanol, inhibited by calpain inhibitor 1, calpain inhibitor II, leupeptin, antipain, iodoacetic acid, and p-(chloromercuri)benzoate, but not affected by pepstatin A and N-ethylmaleimide. Both calpains were inhibited by Fe2+, Fe3+, Ni2+, Cu2+, Zn2+, Cd2+, or Hg2+ but activated by Ca2+, Sr2+, Ba?+, or Mn2+. The m-calpain from grass shrimp was activated, while that from tilapia was inhibited, by Na+, K+, or Mg2+ in the presence of 5 mM calcium. CO2+ activated the calpain from tilapia but inhibited that from grass shrimp. The thermal and frozen stability of calpain from tilapia was higher than that from grass shrimp. The pH stability of both calpains was almost the same