The inhibition of ribonuclease activity and the isolation of polysomes from leaves of the french bean, Phaseolus vulgaris

The effect of inhibitors on the ribonuclease activity of soluble and microsomal fractions of bean leaves has been examined. The soluble ribonuclease activity could be completely inhibited by Zn²⁺, Cu²⁺, bentonite, and diethylpyrocarbonate, although these inhibitors had little effect on the microsomal ribonuclease activity. Ribonuclease activity in the soluble fraction was completely inhibited by guanosine 2′(3′)-monophosphate, which was the first nucleotide to accumulate on degradation of yeast RNA. Adenosine 2′(3′)-monophosphate, the first nucleotide to accumulate on degradation of yeast RNA by the microsomal preparations, completely inhibited the ribonuclease activity of the microsomal fraction.The ribonuclease activity of both enzyme preparations was completely inhibited by an analog of the transition state of the ribonuclease reaction, a complex of guanosine and vanadyl sulfate. Inclusion of this complex in homogenization media markedly increased the proportion of polysomes isolated from bean leaves.