Studies on the Ribonuclease in Posterior Silkglands of Silkworm Larvae, Bombyx mori. : I. Purification and General Properties of the Ribonuclease

Two ribonuclcase active fractions (peak I and peak II) were separated from ammonium sulfate fraction of 0.3 M NaCl extract of posterior silk glands of silkworm by carboxymethy cellulose column chromatography. Peak I and peak II were purified further by carboxymethyl sephadex C-50 column chromatography and by Sephadex G-100 gel filtration, respectively. Purification degree of these two fractions were about 540 and 400 fold as compared with the original, and their recoveries were 2.4 and 2.7 %, respectiveiy. The contamination of phosphomonoesterase and phosphodiesterase w4ere not more than trace. Peak I and peak II were acid ribonuclease. These enzymes had an optimum pH at 5.3 and were not thermostavle. They were inhibited by Mn^<2+>, Ca^<2+> and Na-phosphate and activated by mg^<2+> and Na^+. Further more peak II was inhibited by Zn^<2+>.