Histone hydrolase activity of rat liver lysosomal cathepsin B2

Abstract

1. 1. Histone hydrolase activity of rat liver is mainly localized in the light mitochondrial—lysosomal fraction and is due mainly to cathepsin B2. 2. 2. The rate and extent of histone hydrolysis by cathepsin B2 were higher than those by cathepsin A, C (EC 3.4.4.9) and D (EC 3.4.4.23) and trypsin. 3. 3. The specific activity of cathepsin B2 was much higher on histones than on the basic proteins lysozyme, cytochrome c and protamine sulfate. 4. 4. The DEAE-cellulose column chromatography elution profile, pH-profile, stability properties and the effect of halide ions, sulfhydryl reagents and inhibitors were similar for histone and benzoylarginine amide hydrolase activities, indicating that the activities are due to the same enzyme. 5. 5. The products of cathepsin B2 hydrolysis of arginine-rich histones were separated by Sephadex G-25 column chromatography. Some evidence of endopeptidase activity was shown by the presence of products with molecular weights approximating those of amino acids through hexapeptides.