Novel protease bound with chromatins in normal and tumorous tissues of rats

A protease capable of hydrolyzing casein with optimum pH 10 (alkaline protease), perhaps functional in hydrolysis of non-histone proteins and Hl histone, was found to exist at the state bound with chromatins of various normal and tumorous tissues of rats, in addition to the protease capable of hydrolyzing histone with optimum pH 8 (neutral protease). Alkaline protease was not observed in other subcellular fractions than nuclear fraction. It had approximately 18,000 daltons, and was chymotrypsin-like as inhibited by diisopropyl fluorophosphate, soybean trypsin inhibitor and Chymostatin. Its contents were significantly high in rapidly proliferating cells; Yoshida sarcoma? Rhodamine sarcoma≥ AH 130≥ thymus> spleen? kidney≥ liver? brain.