The hydrolysis of nucleoproteins by cathepsins from calf thymus.

A combination of enzymatic and staining cytological techniques with ultraviolet spectroscopy has suggested the possible participation of nucleoproteins in the synthetic processes of cells (l-4). Little is known concerning the function of enzymes in the intracellular metabolism of nucleoproteins. One approach to the problem has been through the study of the action of enzymes upon nucleoproteins. Mazia, Hayashi, and Yudowitch (5) reported that the separated intracellular proteinases from liver did not hydrolyze the chromosomal proteins of the salivary glands of Drosophila melanogaster, but did hydrolyze the nucleoprotein substrate, chromosin, from calf thymus. Cohen (6) found that several extracellular proteolytic enzymes could hydrolyze the protein in thymus nucleohistone. The hydrolysis of two nucleoprotein preparations of thymus tissue by cathepsin preparations separated from the same tissue is described here.