Liver ribonucleases from the bullfrog, Rana catesbeiana. Purification, properties and changes in activity during...

A major and three minor RNAases exhibiting activity at neutral pH were found in bullfrog liver homogenates. These RNAases were purified to electrophoretic homogeneity. Total purification was 1100 to 1600-fold, and the average recovery was 35%. The molecular weight estimated by gel filtration and SDS-urea-polyacrylamide gel electrophoresis was 12,000 for all the components. An antibody against the major RNAase (component B) reacted with the major RNAase to form a single precipitin line on double immunodiffusion and inhibited the activity of the major RNAase but did not cross-react with the other three components and bovine pancreatic RNAase A. Amino acid analyses revealed that the major RNAase differed markedly from the other three RNAase components in the contents of ten amino acid residues, whereas the minor RNAases were similar to each other. The major RNAase was contained in both frog and tadpole liver and its activity in the liver markedly increased at the metamorphic climax.