Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carboxymethylcellulose, carboxymethylchitin, sulfoethylcellulose and dextrane sulfate interact with pancreatic ribonuclease. In comparison with ribonuclease activity the activity of formed complexes changes differently at the stages of transesterification and hydrolysis, and at each stage the effect of polymers on ribonuclease activity essentially differs. The use of ribonuclease-dextrane sulfate complex in the reaction of uridylyl-(3' leads to 5')-cytidine synthesis demonstrated that the protein synthetic activity completely retained when hydrolytic activity was considerably suppressed.
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PMID:[Modification of pancreatic ribonuclease activity in complexes with polyanions]. 0 Nov 7

In the large granule fraction of rat liver, the density distribution of inhibitor-sensitive neutral ribonuclease is similar to that for acid hydrolases and its density distribution is similarly modified by Triton WR-1339 accumulation in lysosomes. Particulate neutral ribonuclease is latent; the enzyme is unmasked by very low digitonin concentrations or hypoosmotic shock. These observations demonstrate that the bulk of liver neutral ribonuclease is associated with the lysosomal system. In view of the neutral pH optimum of the enzyme and of some particularities of its distribution in fractionation experiments, the possiblilty of an extrahepatic origin of neutral ribonuclease has been investigated. After partial pancreatectomy, a significant decrease is observed in both plasma and liver neutral ribonuclease. The effect is specific, for it does not occur for other lysosomal enzymes. Also, labelled bovine pancreatic ribonuclease, when injected intravenously, is taken up by the liver. The sedimentable labelled enzyme has a density distribution similar to the distribution of other foreign proteins, horseradish peroxidase or yeast invertase. These results are explained by the uptake of plasmatic neutral ribonuclease from pancreatic origin by the liver.
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PMID:Hepatic nucleases. Extrahepatic origin and association of neutral liver ribonuclease with lysosomes. 0 Dec 73

One of the four titrating histidine ring C-2 proton resonances of bovine pancreatic ribonuclease has been assigned to histidine residue 12. This was accomplished by a direct comparison of the rate of tritium incorporation into position C-2 of histidine 12 of S-peptide (residues 1 to 20) derived from ribonuclease S, with the rates of deuterium exchange of the four histidine C-2 proton resonances of ribonuclease S under the same experimental conditions. The same assignment was obtained by a comparison of the NMR titration curves of ribonuclease S, the noncovalent complex of S-peptide and S-protein (residues 21 to 124) with the results for the recombined complex in which position C-2 of histidine 12 was fully deuterated. The second active site histidine resonance was assigned to histidine residue 119 by consideration of the NMR titration results fro carboxymethylated histidines and 1-carboxymethylhistidine 119 ribonuclease. This assignment is a reversal of that originally reported, and has important implications for the interpretation of NMR titration data of ribonuclease.
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PMID:Nuclear magnetic resonance titration curves of histidine ring protons. A direct assignment of the resonances of the active site histidine residues of ribonuclease. 0 54

The reversible thermal denaturation of bovine pancreatic ribonuclease A at pH 5 in 0.1 M NaCl over the range 32-70 degrees C as studied by Raman spectroscopy proceeds in a gradual manner consistent with a stepwise unfolding process rather than as a transition between two states. Conversion of residues from helical or pleated-sheet geometry to some intermediate geometry, as followed by means of the amide I and III lines, reveals that substantial amounts of the helical and pleated-sheet conformations remain at 70 degrees C. Changes in the strength of hydrogen bonding by the tyrosyl residues are indicated by the intensity ratio of the doublet at 830-850 cm(-1) and changes in the geometry of the disulfide bridges by the frequency and half-width of the Raman line near 510 cm(-1) due to the S-S vibration. Vibrations of C-S bonds in the methionines and cystines are used to monitor conformational changes in these residues. While there are small quantitative differences in temperature dependence among these probes, all agree in placing the malting temperature at or near 62 degrees C. The Raman data are quantitatively consistent with the six-stage scheme of unfolding of A.W. Burgess and H.A. Scheraga [(1975), J. Theor, Biol. 53, 403], except that no change in the environment of the tyrosines is seen until 45 degrees C.
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PMID:Laser Raman spectroscopic studies of the thermal unfolding of ribonuclease A. 0 18

Preparations of human leukocyte interferon obtained by multi-stage purification procedure exhibited ribonuclease activity with the optimum at pH 7.0--7.5. The enzyme possessed the endonuclease action mechanism. Most substances studied for their effect on the RNA-ase activity in human interferon preparations showed many of them to act on the enzyme in the same way as on other ribonucleases. However, dithioerythritie, a reducing agent for disulfide bounds, activated the ribonuclease in the interferon preparation, as distinct from the pancreatic ribonuclease, which was inhibited by this preparation. Patterns of protein and RNA-ase distribution were obtained by electrophoresis in polyacrylamide gel.
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PMID:[Ribonuclease activity in preparations of human leukocyte interferon]. 0 77

A chemical derivative of bovine pancreatic ribonuclease A (RNase A) has been prepared by reaction with fluorescein-isothiocyanate at pH 6. This derivative has a fluorescein group covalently attached to the alpha-amino group of the protein. The enzymic properties of the modified protein are similar to those of RNase A. It is shown that the pK of the fluorescein group can be used as an index of protein conformation to monitor structural changes in the protein. In this work, the binding of a specific inhibitor (cytidine 2'-monophosphate) to RNase A, the isomerization process occurring in RNase A around pH 6, and the thermal unfolding of RNase A, were studied by mean of the pK changes of the fluorescein group. The results obtained by this method are fully consistent with those obtained by other methods. It is proposed that using ionizable reporter groups and their changes in pK to monitor conformational changes in proteins may be a sensitive tool both in equilibrium and kinetic studies.
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PMID:pK changes of ionizable reporter groups as an index of conformational changes in proteins. A study of fluorescein-labelled ribonuclease A. 1 42

Kethoxal (3-ethoxy-2-ketobutanal) reacts with the guanidino group of Nalpha-acetylarginine to produce four derivatives, reactive to periodate, stable at pH 7, with 15% reverting to arginine on acid hydrolysis. Other amino acids with blocked alpha-amino groups do not react, except the epsilon-amino of lysine (slowly). The pK of the mixed Kethoxal-Nalpha-acetylarginine derivatives is 5.8-6.1. Kethoxal reacts at neutral pH with arginyl residues of bovine pancreatic ribonuclease A. In the presence of an active-site ligand, arginine-39 and arginine-85 react at about equal rates. The loss of enzymic activity at pH 7 is proportional to the combined loss of these residues. The enzymic activity toward RNA is 20-25% of that of native RNAase at pH 7, and 90-100% at pH 5. In the absence of an active site ligand, arginine-10 is also modified with the loss of almost all enzymic activity, although arginine-10 is not an active-site residue. Arginine-33 is unreactive. Kethoxal-modified RNAase undergoes cross-linking in solution at pH 7 or in the freeze-dried state, Incubation at pH 9 in the presence of homoarginine results in partial regeneration of arginyl residues and activity at pH 7. Kethoxal modification of arginines-39 and -85 appears to raise the pK of lysine-41 by about 1 unit, as indicated ty the pH dependence of arylation by 2-carboxy-4,6-dinitrochlorobenzene. The claims of Patthy and Smith (J. Biol, Chem. (1975) 250, 565-569), and of Takahashi (J. Biol. Chem. (1968) 243, 6171-6179) that arginine-39 is a more important functional residue than is arginine-85 are questioned.
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PMID:Modification of amino acids and bovine pancreatic ribonuclease A by kethoxal. 1 99

Four urinary alkaline ribonucleases (RNase, EC 3.1.4.22) were purified from patients with nephrotic syndrome using phosphocellulose, DEAE-cellulose and Sephadex G-75 chromatographiy. These enzymes were designated as RNases 1--4, respectively, in order of elution on phosphocellulose chromatography. The respective purification of each fraction was 41-, 23-, 34- and 27-fold with a total recovery of 25%. The pH optima of these RNases were around 8.5 with Tris/HCl buffer and the reaction was activated by mono- and divalent cations, such as Na+, K+, Mg2+ and Ca2+, but inhibited by Fe2+, Cu2+ and Zn2+. EDTA had little effect on the velocity of reaction. The molecular weights of RNases 1--4 were estimated by gel filtration as 45 000, 32 000, 20 000, and 13 000, respectively. Each enzyme hydrolyzed pyrimidine nucleotides preferentially with higher affinity for poly(C) than poly (U) as determined with synthetic polymers and was free from other nucleolytic enzymes. The patients with renal disorders excreted one to four RNases in urine and the number of enzymes increased as the concentration of urinary protein increased. On the other hand, normal subjects excreted a single fraction essentially identical to RNase 1.
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PMID:Purification and properties of urinary alkaline ribonucleases from patients with nephrotic syndrome. 1 98

The acid denaturation of bovine pancreatic ribonuclease A in the presence of 0.2M sodium dihydrogen phosphate has been studied by n.m.r. spectroscopy. Phenylalanine, tyrosine and methionine resonances serve as monitors of the unfolding process. It is shown that the inhibitor shifts the equilibrium towards the native structure at acid pH. Exchange broadening of the C-2 resonances of the active site histidines, 12 and 119, occurs in the presence of phosphate, suggesting an equilibrium between native and unfolded structures. Stabilisation of the partially unfolded protein is observed at pH 1.5, as evidenced by the lack of the histidine resonance due to random coil protein. A scheme of the equilibria relating the various states of the protein is proposed.
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PMID:Stabilisation of enzyme structures by inhibitors. A nuclear magnetic resonance study of the effect of phosphate on the acid unfolding of ribonuclease A. 1 21

A recent conclusion that beef pancreas contained a molecular species of ribonuclease with intrinsically high activity at pH 4.5 has been found to be incorrect. The particular assay used in the earlier experiments gives anomalous results at acid pH in the presence of low concentrations of ions such as phosphate which was used during the fractionation. By turning to the more widely employed form of the perchloric acid precipitation assay, interference is avoided and the ribonuclease in beef pancreas is confirmed as consisting almost completely of the molecular species well-characterized as ribonuclease A. The clarification of the assay question permits a clear interpretation of the results of each step of the chromatographic purification procedure that led to the initial conclusion, including an artifact that arose when gel filtration was attempted with distilled water rather than with buffer.
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PMID:Explanation of the observation of pancreatic ribonuclease activity at pH 4.5. 1 66


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