Spleen ribonuclease

It should be pointed out that the successful purification of spleen exonuclease (11) was greatly helped by use of a DNA hydrolyzate produced by spleen acid DNase as the substrate, since the synthetic substrates are nonspecific, and RNA core (the water-undialyzable ribooligonucleo-tides obtained by exhaustive digestion of RNA with pancreatic RNase) is also hydrolyzed by both acid and basic spleen ribonucleases (38, 39). Spleen exonuclease is unable to hydrolyze cyclic phosphates (14). 

Oligosaccharides from glycopeptides by hydarazinolyses Derivatization 2-pyridylamine dimethylamine/borane D FI Aex = 320 nm Aem = 380 nm C Fused silica (60 cm x 50 pm i.d.) polyimine coated E 100 mmol 1 phosphate, pH 2.5 200 mmol I borate V 20 kV Glycopeptides obtained by trypsine digestion of human transferrin, serum fetuin, human immunoglobulin, bovine, spleen ribonuclease, yeast invertase... 

An enzyme having catalytic properties and heat stability characteristics similar to those of pancreatic ribonuclease has been purihed from calf spleen and has been found in calf Uver. However, the spleen ribonuclease had a different pH optimum and is separable from pancreatic ribonuclease on a column of cation exchange resin 166). Ribonucleases, with different specificities, have also been described in a variety of animal and plant tissues 157,168), and several ribonucleases of Aspergillus oryzae have been purified and studied 159-161). 

Acid phosphatase r kidney < spleen Ribonuclease Glutamine synthetase pancreas I brain... 

The most convincing evidence in favor of a uniform 3,5-diester linkage between nucleotides has been obtained by the action of various enzymes on synthetic diesters of known constitution.218 217 Ribonuclease and spleen extracts were found to act only on nucleoside 3-(benzyl hydrogen phosphates), but not on other isomers, to give nucleoside cyclic phosphates which are broken down further to give nucleoside 3-phosphates. It is concluded, by analogy, that polynucleotides, which are substrates for these enzymes, also possess ester groupings at the 3-positions, rather than at the... 

The question of enzyme specificity for irradiated polynucleotides is taken up in more detail in the recent review of Johns.11 The specificities of four enzymes, spleen phosphodiesterase, snake venom phosphodiesterase, pancreatic ribonuclease, and pancreatic deoxyribonuclease are discussed. 

This final acid phosphatase preparation had a specific activity of 468 and represented an approximately 1900-fold purification of the acid phosphatase in the starting crude spleen nuclease II. It contained no acid deoxyribonuclease, acid ribonuclease, exonuclease, and phosphodiesterase activities that could be detected in a 0.1-ml sample after 2 hours of incubation with the appropriate substrate. The relative rates of hydrolysis of various substrates were as follows p-nitrophenyl phosphate, 100 5 -AMP, 63 j8-glycerophosphate, 60 ATP, 0. With p-nitrophenyl phosphate as substrate, the pH optimum was broad and lay between pH 3.0 and pH 4.8. The Michaelis constant at 37°C was 7.25 X 10" mM. Phosphate and chloride ions acted as competitive inhibitors. 

Many other ribonucleases have been described. They differ with respect to specificity toward various internucleotide bonds, in heat stabilities, and in pH optima. In 1949 Maver and Greco (M8) reported the presence in extracts of spleen of a heat-labile nuclease that had a pH optimum of approximately 5.2 in the presence of magnesium, and 6.6 in the absence of magnesium. That this was a different enzyme entirely from pancreatic RNase was shown most dramatically by Hilmoe and Heppel (H7), who found that this enzyme was able to hydrolyze the limit polynucleotide obtained by exhaustive treatment of RNA with ribonuclease I. The ubiquity of ribonucleases can perhaps best be demonstrated by noting... 

Purification of bull seminal plasma hyaluronidase Purification of ribonuclease B Purification of biliary glycoprotein I Separation of human amylase isoenzymes Purification of cathepsin D from rat spleen Purification of a cathepsin E-like acid proteinase from rat spleen... 

An enzyme isolated from spleen shows the same specificity as pancreatic ribonuclease. This enzyme differs only in certain physical properties from the pancreatic enzyme. It has been used to show the intermediate formation of cyclic-ended oligonucleotides. Previous studies with pancreatic ribonuclease had been carried out under conditions that could... 

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