Limited Autolysis of Ca2+-Activated Neutral Protease (CANP) Changes Its Sensitivity to Ca2+ Ions

Abstract
Ca2+-activated neutral protease (CANP) usually requires mM Ca2+ for activation. The sensitivity of CANP to Ca2+ is greatly enhanced by passing it through a casein-Sepharose column in the presence of Ca2+ ions. This conversion is ascribed to autolysis of CANP. The converted enzyme required 40 μM Ca2+ for 50% activation. Various properties of the converted enzyme were very similar to those of CANP-I, recently found in canine heart muscle. Names of “m-CANP” and “μ-CANP” are proposed for CANPs which require mM and μM order Ca2+ for activation, respectively.