The Nuclease Activities of Cathepsin Preparations from Calf Spleen and Thymus

In a study of the role of cathepsins in nuclear metabolism (1) these intracellular proteinases were found to hydrolyze thymus nucleoproteins and render dialyzable the desoxyribonucleic acid. Further characterization of this nuclease activity of the cathepsin preparations revealed pH optima in the acid range for both desoxyribonucleic acid (DNA) and ribonucleic acid (RNA). This was in contrast to the specific activities of the pancreatic nucleases which show pH optima above neutrality (24). Evidence which establishes an intracellular desoxyribonuclease and ribonuclease activity distinct from that of the pancreas and a correlation of the factors which affect the proteolytic and nuclease activities of the cathepsin preparations are reported here.