Purification and partial characterization of two forms of Ca2+-activated neutral protease from calf brain...

Two forms ( CANP1 and CANP2 ) of a calcium activated neutral protease (CANP) have been purified to near homogeneity from calf brain synaptosomes and spinal cord. The procedure involves ammonium sulfate fractionation of the brain synaptosome or spinal cord cytosol followed by chromatography on DEAE-Sephacel, Hydroxylapatite and alpha-casein-CH-Sepharose 4B affinity gel. The molecular mass of each of the proteases is 78,000 as judged on SDS-PAGE. A protein with apparent molecular mass of 17,000 copurifies with each of the proteases. CANP1 was maximally active at 600 microM while CANP2 exhibited maximum activity at about 2 microM Ca2+. Both of the proteases were inhibited by sulfhydryl modifying agents and leupeptin.