The purification and characterisation of m-calpain from ostrich brain

Calpains are intracellular cysteine proteases activated in a Ca 2+ -dependent manner. The purpose of the present study was to investigate the physico-chemical and kinetic properties of ostrich brain m-calpain. m-Calpain was purified by successive chromatographic steps on Toyopearl-Super Q 650s and Pharmacia Mono Q HR 5/5 columns. A Ca 2+ concentration of 5 mM and a casein concentration of 5 mg/ml were found to be necessary for optimum calpain activity. Ostrich m-calpain exhibited a M r of 84 K using SDS-PAGE and a M min of 79.3 K from amino acid analysis. The pH and temperature optima were found to be 7.5 and 37 °C, respectively. The amino acid composition of m-calpain revealed 700 residues. The N-terminal sequence of m-calpain showed sequence identity with chicken (27%), human (23%) and rabbit (18%) and Schistoma mansoni (9%).