A Comparative Study on Enzymatic Activity of Bovine Pancreatic Ribonuclease <italic>A</italic>, Ribonuclease <italic>S</italic> and Ribonuclease <italic>S</italic><xref ref-type="fn" rid="fn1"><sup>*</sup></xref>

The enzymatic activity of subtilisin-produced derivatives of ribonuclease A (RNase A) [EG 2. 7. 7. 16, ribonucleate pyrimidinenuclcotido2′-transferase (cyclizing)], ribonuclease S (RNase S) and ribonuclease S (RNase S), has been compared with that of the original enzyme using RNA and synthetic low-molecular weight nucleotide derivatives as substrates at varying pH's and temperatures. 1. Whenever low-molecular weight compounds were used as substrates, pH optimum of each of the modified enzymes for both the steps of cyclization and hydrolysis shifted to more neutral side than that of the original enzyme. The pH optimum at 16°G was 6.5 for RNase S, 5.5 for RNase A and between 6.5 and 5.5 for RNase S. The shifts in pH optimum of both the modified enzymes at 37°C were less remarkable than those at 16°C. 2. When RNA was used as substrate, three RNases showed an identical pH optimum of 8.0 at 16°G as well as 37°C. 3. Specific activities of the three enzymes increased in an order of RNase A