Human senile cataractous lens protease. Isolation and some chemical characteristics.

A proteolytic enzyme was isolated from human senile cataractous lens by anion-exchange and gel-filtration chromatography. Sedimentation and zone-electrophoretic experiments indicated a high degree of homogeneity for the enzyme. A molecular weight of 27000 was calculated from measurements of sedimentation velocity and diffusion coefficient. Chelating agents decreased activity which could be restored by addition of certain bivalent metal ions. Di-isopropyl phosphorofluoridate and phenylmethanesulphonyl fluoride inhibit the proteolytic activities. Optimum rates of hydrolysis were observed at pH5.2.