Purification and characterization of a calcium-activated neutral protease from rabbit skeletal muscle which requires calcium ions of microM order concentration.

One form of calcium-activated neutral protease (CANP) highly sensitive to calcium ions was purified by column chromatographic procedures to homogeneity. The purified enzyme required microM order Ca2+ (mu CANP), and the half-maximum activity was attained at 50 microM Ca2+. The electrophoretic mobility in a non-denaturing buffer showed that this enzyme is less acidic than another CANP which required mM order Ca2+ (mCANP). On SDS-polyacrylamide gel electrophoresis, the enzyme separated into two components with molecular weights of 79,000 and 28,000, respectively. Of these, the former was slightly larger than the counterpart of mCANP (Mr 76,000). Thus, mu CANP cannot be derived from mCANP by limited autolysis.