Nuclease activity of ribosomal and soluble fractions of Acheta domesticus

Acheta domesticus ribosomes, microsomes, the soluble fraction, and several of its derivatives, including a pH 5 enzymes fraction, transfer enzymes, and a preparation containing transfer and amino-acid-activating enzymes, were assayed for the presence of nucleases. All components possessed RNA-degrading capacity; optimal activity was observed at pH 5·5 and 7·8. Nuclease contamination of ribosomes could be reduced when isolation was carried out in the presence of bentonite. Ribosomes prepared in the presence of bentonite possessed nuclease activity equivalent to 2·3 mμg of pancreatic ribonuclease/mg protein, when assayed in 0·05 M Tris buffer at pH 7·8. At pH 5·5 the ribosomal nuclease was inhibited by Mg 2+ and stimulated by low concentrations of K +; at pH 7·8 both cations were inhibitory at all concentrations tested.