Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Highly purified platelet glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) can be modified in its isoelectric point and its molecular specific activity by extracts of some leukemic granulocytes. The "G6PD modifying factors" are relatively small molecules (molecular weight slightly under 5000), thermostable, dialyzable, and ultrafilterable. These molecules are destroyed by various endo- and exopeptidases and by serine enzymes present in crude extracts of leukocytes and commercial preparations of ribonuclease. The alterations of platelet G6PD due to the "G6PD modifying factors" are stable and not reversible by dialysis or further chromatography. The leukemic extracts which are able to modify G6PD also can modify the electrophoretic mobility and (or) the enzymatic activity of purified leukocyte pyruvate kinase, 6-phosphogluconate dehydrogenase, and glucosephosphate isomerase. The chemical nature of such modifications and their relationships with post-translational modifications which occur in leukemic or normal cells are discussed.
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PMID:Modifications of purified glucose-6-phosphate dehydrogenase and other enzymes by a factor of low molecular weight abundant in some leukemic cells. 0 52

Specific beta-adrenergic receptors present in membrane preparations of frog erythrocytes were identified by binding of (-)-[3H]dihydroalprenolol, a potent competitive beta-adrenergic antagonist. The (-)-[3H]dihydroalprenolol binding sites could be solubilized by treatment of a purified erythrocyte membrane fraction with the plant glycoside digitonin but not by treatment with a wide variety of other detergents. The binding sites appeared to be soluble by several independent experimental criteria including (a) failure to sediment of 105,000 X g for 2 hours; (b) passage through 0.22-mu Millipore filters; (c) chromatography on Sepharose 6B gels; and (d) electron microscopy. The soluble receptor sites retained all of the essential characteristics of the membrane-bound sites, namely rapid and reversible binding of beta-adrenergic agonists and antagonists; strict stereospecificity toward both beta-adrenergic agonists and antagonists; appropriate structure-activity relationships; saturability of the sites at low concentrations of ligand; no affinity for alpha-adrenergic drugs, nonphysiologically active catechol compounds, and catecholamine metabolites. Based on gel chromatography in the presence of detergent, the molecular weight of the soluble receptor is estimated to be no greater than 130,000 to 150,000. Equilibrium binding studies indicated a KD for the soluble receptor of 2 nM. Hill coefficients (nH) of 0.77 and curved Scatchard plots suggested the presence of negatively cooperative interactions among the solubilized receptors in agreement with previous findings with the membrane-bound sites. Kinetic studies indicated an association rate constant K1 = 3.8 X 10(6) M-1 min-1 and a reverse rate constant k2 = 2.3 X 10(-3) min-1 at 4 degrees. The kinetically derived KD (k2/k1) of 0.6 nM is in reasonable agreement with that determined by equilibrium studies. The soluble receptors were labile at temperature greater than 4 degrees but could be stabilized with high concentrations of EDTA. Guanidine hydrochloride and urea produced concentration-dependent losses of binding activity which were partially reversible upon dialysis. Trypsin and phospholipase A both degraded the soluble receptors but a variety of other proteases and phospholipases as well as DNase and RNase were without effect. Experiments with group-specific reagents indicated that free lysine, tryptophan, serine, and sulfhydryl groups may be important for receptor binding. These studies suggest that the receptor is probably a protein which requires lipids for functional integrity. Data obtained with the solubilized binding sites are consistent with the contention that these sites represent the physiologically relevant beta-adrenergic receptors which have been extracted from the membranes with full retention of their properties.
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PMID:Solubilization and characterization of the beta-adrenergic receptor binding sites of frog erythrocytes. 0 47

From experiments with glycoproteins containing the glycopeptide linkages, arabinose-O-hydroxyproline and galactose-O-serine (plant cell wall glycopeptides), N-acetylgalactosamine-O-serine/threonine (pig submaxillary mucin), and N-acetyl-glucosamine-N-asparagine (fetuin), it is apparent that anhydrous liquid HF, a reagent commonly used by snythetic peptide chemists for the complete removal of protecting groups from synthetic peptides, cleaves the O-glycosidic linkages of neutral sugars in 1 hr at 0 degrees C, and the O-glycosidic linkages of amino sugars in 3 hr at 23 degrees C. The N-glycosidic linkage of N-acetylglucosamine to asparagine is not cleaved under any conditions that have been tested. Sodium dodecyl sulfate gel electrophoresis of bovine serum albumin treated in HF does not show any degradation of peptide bonds. Some relatively stable enzymes (lysozyme and RNase) have been shown by others to retain most of their enzymic activity after short treatment (1 hr at 0 degrees C) in HF. With the specificity of HF at 0 degrees C for neutral sugars it should be possible to generate di- or trisaccharides in high yield from polysaccharides containing both neutral and amino sugars with neutral sugars as the reducing termini.
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PMID:A new approach to the structural determination of glycoproteins and polysaccharides: anhydrous HF solvolysis. 7 2

Endogenous protein kinase activity was detected in the outer plasma membrane of 373 and SV40 transformed 3T3 cells. When intact cells were incubated with [gamma-32P]ATP, there was a transfer of [32P]phosphate into an acid-insoluble product. The reaction was: (a) linear as a function of time (up to 30 min), (b) proportional to the number of cells present and (c) dependent on temperature and Mg2+ concentration. The acid-insoluble product was susceptible to pronase but not RNase or DNase. More specifically, phosphomonoester bonds to serine and threonine were identified. There was less than 3% hydrolysis of the [gamma-32P]ATP during the reaction; moreover, free [32P]phosphate failed to substitute for the ATP. The reaction product was located on the cell surface, as evidenced by the fact that it could be removed by mild trypsin treatment of intact 3T3 cells. Further evidence for the surface location of the kinase was shown by its activity in phosphorlating exogenous substrate, histone, and phosvitin. The level of phosphorylation increased by 2- to 4-fold prior to the start of S phase when quiescent 3T3 cells were stimulated to reinitiate growth by the addition of serum. The SV40 3T3 cells had from 5- to 10-fold more activity per cell than the quiescent 3T3 cells. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and radioautography show at least 25 phosphorylated proteins; the surface label pattern of 3T3 cells differs from that of SV40-transformed 3T3 cells.
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PMID:Endgoenous protein kinase in outer plasma membrane of cultured 3T3 cells. Nature of the membrane-bound substrate and effect of cell density, serum addition, and oncogenic transformation. 18 98

T1 ribonuclease digestion of yeast tRNASer in the presence of seryl tRNA synthetase was used for monitoring the relationship between the substrate binding sites on the synthetase. It was found that (a) ATP displaces the tRNA from the synthetase with an effector affinity constant corresponding to the Km for ATP of 10 micron; (b) AMP and a number of nucleoside triphosphates, while influencing the rate of aminoacylation, do not displace the tRNA from the enzyme; (c) ADP and PPi inhibit the aminoacylation and the binding of tRNASer; (d) adenylyl diphosphonate is bound to the synthetase and lowers the protection of the tRNA against the nuclease attack in a similar way as does ATP; (e) interactions between the sites of L-serine and tRNASer could only be shown when both sites for serine were saturated and, in addition, the ATP analog or ADP was present. It is concluded that in seryl tRNA synthetase binding sites for ATP interact with the ones for tRNA as well as with the ones for serine. These findings contribute to the understanding of the mechanism of aminoacylation.
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PMID:Yeast seryl tRNA synthetase: interactions between the ATP binding site and the sites for tRNASer and L-serine. 41 97

The amino acid sequences of the pancreatic ribonucleases from river-breed water buffaloes from Italy and swamp-breed water buffaloes from Indonesia differ at three positions. One of the differences involves a replacement of asparagine-34, with covalently attached carbohydrate on all molecules, in the river-breed enzyme by serine in the swamp-breed enzyme. The ribonuclease content of the pancreas differs considerably between breeds and is lower in river buffaloes. A ribonuclease preparation from two swamp buffaloes contained a minor glycosylated component. Preliminary evidence was obtained that the amino acid sequence of this component has factors in common with the main component of the swamp-breed ribonuclease and with the river-breed enzyme.
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PMID:Amino acid sequence differences in pancreatic ribonucleases from water buffalo breeds from Indonesia and Italy. 54 6

Red kangaroo (Macropus rufus) ribonuclease was isolated from pancreatic tissue by affinity chromatography. The amino acid sequence was determined by automatic sequencing of overlapping large fragments and by analysis of shorter peptides obtained by digestion with a number of proteolytic enzymes. The polypeptide chain consists of 122 amino acid residues. Compared to other ribonucleases, the N-terminal residue and residue 114 are deleted. In other pancreatic ribonucleases position 114 is occupied by a cis proline residue in an external loop at the surface of the molecule. Other remarkable substitutions are the presence of a tyrosine residue at position 123 instead of a serine which forms a hydrogen bond with the pyrimidine ring of a nucleotide substrate, and a number of hydrophobichydrophilic interchanges in the sequence 51-55, which forms part of an alpha-helix in bovine ribonuclease and exhibits few substitutions in the placental mammals. Kangaroo ribonuclease contains no carbohydrate, although the enzyme possesses a recognition site for carbohydrate attachment in the sequence Asn-Val-Thr (62-64). The enzyme differs at about 35-40% of the positions from all other mammalian pancreatic ribonucleases sequenced to date, which is in agreement with the early divergence between the marsupials and the placental mammals. From fragmentary data a tentative sequence of red-necked wallaby (Macropus rufogriseus) pancreatic ribonuclease has been derived. Eight differences with the kangaroo sequence were found.
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PMID:The amino-acid sequence of kangaroo pancreatic ribonuclease. 65 39

Modification of hen egg-white lysozyme by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide in presence of 4-phenylbutylamine yielded derivatives, which contained 0.6--0.7 modified residues and retained about 60% of the original activity. Kinetic studies revealed that the modified-lysozyme increases approx. 20-fold the kcat of hydrolysis of SucGly2Phe-4-nitroanilide by alphachymotrypsin, without changing the Km. The apparent dissociation constant of phenylbutylamine-modified lysozyme . chymotrypsin complex was found to be 0.03 mM and independent of substrate concentration. The accelerating effect of the modified lysozyme was also observed with other p-nitroanilide substrates of alpha-chymotrypsin. However, the hydrolysis of other substrates, acylation by active site titrant or inhibition by irreversible or competitive inhibitors were uneffected. The enhancing effect of the modified lysozyme seems to be very specific since other chymotrypsin-like enzymes, or serine proteinases except delta-chymotrypsin, were not influenced and phenylbutylamine derivatives of alpha-lactalbumin or ribonuclease were lacking any enhancing effect. Smaller, but significant enhancing effect was found also in lysozyme substituted by benzylamine, beta-phenylethylamine and tryptamine and in inactive derivatives of lysozyme substituted by phenylbutylamine. Competitive inhibitors of lysozyme such as N-acetyl-D-glucose amine oligomers, (GlcNAc)2 and (GlcNAc)3 abolished partially the accelerating effect of phenylbutylamine-modified lysozyme, indicating that the substituted group is located in the vicinity of the binding site.
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PMID:Enhancement of alpha-chymotrypsin-catalyzed hydrolysis of specific p-nitroanilide substrates by 4-phenylbutylamine derivative of hen egg-white lysozyme. 71 65

Previous studies have shown that a membrane preparation from hen oviduct catalyzes transfer of oligosaccharide from oligosaccharide-P-P-dolichol to denatured RNase and alpha-lactalbumin. To gain further insight into the structural requirements of a protein that allow it to serve as a substrate for glycosylation, the acceptor ability of a variety of other modified proteins containing the tripeptide sequence-ASN-X-(SER/THR)-has been investigated. Of 7 proteins tested, 2 (ovine prolactin and rabbit muscle triosephosphate isomerase) could be enzymatically glycosylated by a particulate preparation from hen oviduct. The remaining 5 proteins, assayed as either S-carboxymethylated or S-aminoethylated derivatives, were inactive as carbohydrate acceptors. However, cyanogen bromide treatment of 2 of the inactive proteins, bovine catalase and concanavalin A from jack bean, yielded peptide fragments which served as substrates for glycosylation. These results suggests that for some proteins, disruption of the tertiary structure is sufficient to allow attachment of carbohydrate. Other denatured proteins may possess additional restrictions imposed by their secondary structure. In certain cases, these restrictions are removed when the polypeptide chain is fragmented.
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PMID:Enzymatic conversion of proteins to glycoproteins by lipid-linked saccharides: a study of potential exogenous acceptor proteins. 73 7

An ovarian cystadenocarcinoma-associated antigen (OCAA) was found to be common to all serous and mucinous cystadenocarcinomas of the ovary. It was apparently absent in tissues of normal reproductive organs. Furthermore, OCAA was not detected in benign ovarian serous and mucinous cyst-adenomas or in any other gynecologic or nongynecologic cancers thus far tested. The antigenic determinant of OCAA was immunologically unrelated to the carcinoembryonic antigen, other known tumor antigens, or the histocompatibility antigens. We purified and partially characterized OCAA. The antigen was a high-molecular-weight glycoprotein soluble in 0.6 M perchloric acid. It consisted of about 50-60% protein (based on dry wt). Amino acid composition in OCAA was characterized by a high percentage of threonine, serine, proline, and valine. Galactose and N-acetylglucosamine were the principal carbohydrate constituents. The antigenic activity was resistant to treatment with trypsin and protease and also to treatment with DNase, RNase, and N-acetylneuraminidase. The antigenicity was considerably reduced by mild periodate oxidation.
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PMID:Tumor-associated antigen for cystadenocarcinomas of the ovary. 82 81


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