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:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nuclear magnetic quadrupole relaxation appears to be a general method for studying the binding of anions to proteins. This is shown by the increase in transverse quadrupole relaxation rate of 35Cl- and 81Br- in the presence of horse liver alcohol dehydrogenase, lysozyme, trypsin, alpha-chymotrypsin, human carbonic anhydrase, fructose-1,6-bisphosphate aldolase and human serum albumin. Of the many possible binding sites at the surface of a protein (e.g. positively charged amino acid side-chains) only a few account for the main part of the relaxation enhancement. This is shown by the decrease in 35Cl- and 81Br- relaxation rate on addition of functional ligands. Large, kinetically inert, complex anions like Pt(CN)2-4 and Au(CN)-2 are found to act as strong competitors towards halogen ions for the high-affinity anion binding sites of a number of proteins. Titrations with complex anions following the 35Cl- or 81Br- relaxation rates are found to be helpful in attempts to elucidate binding mechanisms. Especially, the complex anions may be useful probes for the discrimination between general and metallic anion binding sites in proteins and they also permit correlation of information from X-ray investigations of crystals with that from physical measurements in solution. From the change in halide ion quadrupole relaxation rate on addition of strongly binding ligands the quadrupole coupling constants of the high affinity Cl- and Br- binding sites are estimated using certain assumptions. It is found that for several proteins, comprising the metal-free proteins but also alcohol dehydrogenase and Escherichia coli alkaline phosphatase, the 35Cl quadrupole coupling constants have approximately the same values. For some other metallo-proteins like carbonic anhydrase and a zinc - serum-albumin complex considerably greater quadrupole coupling constants were obtained. The estimated quadrupole coupling constants are used as a basis for a discussion of the interactions involved in anion-protein interactions.
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PMID:Pt(CN)2-4 and Au(CN)-2: potential general probes for anion-binding sites of proteins. 35Cl and 81Br nuclear-magnetic-resonance studies. 120 23

Pepsin successfully catalyzed the synthesis of several peptide derivatives from N-protected di- or tripeptides and amino acid or peptide esters or p-nitroanilides in dimethylformamide-water solutions at pH 4.6. An optimal substrates:pepsin ratio depended on the structure of starting peptides, especially their fit to the substrate binding sites of the enzyme. For hexapeptide Z-Ala-Ala-Phe-Leu-Ala-Ala-OCH3 formation, an equilibrium yield was attained at 1:3.10(5) enzyme-substrates ratio that indicated high efficiency of pepsin in synthesis reactions. In the course of the equilibrium peptide synthesis, pepsin gradually disappeared from the liquid phase due to its entrapment within a gel, formed by the hexapeptide product, while retaining its activity. The inclusion into the precipitate was not specific for pepsin, so far as inert proteins, lysozyme, ribonuclease A and carbonic anhydrase, when added to the reaction mixture, became also co-precipitated with the hexapeptide formed. It appears that co-precipitation of pepsin, an important factor limiting the enzyme efficiency, might be operative as well for other proteinases used to catalyze peptide synthesis.
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PMID:Pepsin as a catalyst of peptide synthesis. Enzyme co-precipitation with emerging peptide products. 142 33

The relative susceptibilities of lenticular proteins (alpha, beta and gamma-crystallins) and a number of proteins of non-lenticular origin, to hydroxyl radical-mediated peptide bond cleavage were compared. The non-lenticular proteins (bovine serum albumin, ovalbumin, alcohol dehydrogenase, lysozyme, thyroglobulin, beta-amylase, haemoglobin and carbonic anhydrase) were readily cleaved into acid-soluble fragments following 5 hours treatment with copper ions and hydrogen peroxide. In contrast the crystallins were almost totally unaffected by similar treatment. When alpha-crystallin was pre-treated with acid or cleaved into large fragments with cyanogen bromide it became susceptible to hydroxyl radical attack, yet heating the protein did not diminish its resistance. It is suggested that the resistance of alpha-crystallin to the copper/peroxide-mediated fragmentation may be dependent on the conformation of the protein.
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PMID:Differences in susceptibility between crystallins and non-lenticular proteins to copper and H2O2-mediated peptide bond cleavage. 175 88

We have developed a technique which utilizes matrix-assisted laser desorption mass spectrometry to study the subunit association of proteins. Aqueous protein samples are treated with a dilute solution of glutaraldehyde, a cross-linking agent which reacts with free amino groups on proteins. This agent effectively traps the multimeric form, preventing it from dissociating in the sample preparation and desorption process. Proteins measured include lysozyme, carbonic anhydrase, apomyoglobin, glucose 6-phosphate dehydrogenase, ovine lutropin, yeast alcohol dehydrogenase, avidin and pyruvate kinase. Dimeric and tetrameric complexes up to 250,000 Da have been measured in this manner.
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PMID:Assessing the multimeric states of proteins: studies using laser desorption mass spectrometry. 181 90

It has been shown that in the course of equilibrium peptide synthesis pepsin gradually disappeared from the liquid phase due to its entrapment within a gel formed by the hexapeptide product, while retaining its activity. The inclusion into the precipitate was not specific for pepsin so far as inert proteins-lysozyme, ribonuclease A and carbonic anhydrase, when added to the reaction mixture, became also co-precipitated with the hexapeptide formed. It appears that co-precipitation of pepsin-an important factor limiting the enzyme efficiency, might be operative as well for other proteinases used to catalyze peptide synthesis.
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PMID:Pepsin behavior as a catalyst in equilibrium-controlled peptide synthesis. 182 70

A method for determination of amino acid composition of proteins separated by SDS-polyacrylamide gel electrophoresis and transferred to polyvinylidene difluoride (PVDF) membranes is described. A single blotted band containing 50 to 200 pmoles of protein was cut out and submitted to acid hydrolysis with HCl followed by derivatization with phenylisothiocyanate. The amino acid derivatives were separated by reverse phase high-performance liquid chromatography. Bovine serum albumin, lysozyme, myoglobin, ovalbumin, soybean trypsin inhibitor and carbonic anhydrase were analyzed; the results revealed a good correspondence with reported values. This can be considered an analytical method to determine the amino acid composition of samples from microquantities of protein mixtures, particularly in those cases in which SDS-polyacrylamide gel electrophoresis is the most suitable separation system.
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PMID:Micro-determination of amino acid composition of proteins electroblotted onto polyvinylidene difluoride membranes. 263 61

To examine the effects on protein and electrolyte reabsorption of reducing the energy supply to the proximal tubules, an inhibitor of the citric acid cycle, maleate (600 mg.kg-1), was administered to anesthetized dogs during continuous ethacrynic acid infusion. One hour after infusion, maleate reduced renal oxygen consumption from 128 +/- 3 to 48 +/- 6 mumol.min-1. Comparisons at similar GFR showed that maleate reduced bicarbonate reabsorption by 65%, chloride reabsorption by 60% and phosphate reabsorption by 90%. Tubular reabsorption of lysozyme, determined by the 'trapped-label' method, was reduced by 97%. Total protein excretion in urine increased from 0.12 to 1.0 mg.min-1 and was not associated with a significant increase in brush border and lysosome marker enzymes. However, by superimposing a carbonic anhydrase inhibitor, acetazolamide (100 mg.kg-1), electrolyte reabsorption was slightly further reduced but protein excretion increased to 2.7 mg.min-1, coincidentally with a dramatic increase in enzyme excretion: approximately 20-fold in the brush border enzymes, alanine aminopeptidase and alkaline phosphatase, and 10-fold in the lysosomal enzymes, acid phosphatase and N-acetyl-beta-glucosaminidase. Our data indicate that maleate stops protein reabsorption without signs of acute tubular damage, whereas subsequent administration of acetazolamide results in tubular desquamation and albumin leakage.
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PMID:Effect of maleate on tubular protein reabsorption in dog kidneys. 323 92

Earlier studies have indicated the marked resistance of two pronase endopeptidases to denaturation in high concentrations of urea or guanidine hydrochloride (Siegel, S., and Awad, W. M., Jr. (1973) J. Biol. Chem. 248, 3233--3240). One component has only a single residue of lysine and the other has none. The consideration arose that lysine-containing peptide segments may be less stable than those containing arginine because of the fluctuations of the side groups of the former residue. The small epsilon amino groups may not be able to sustain solvation of the hydrophobic arm in an aqueous medium. Arginine residues have shorter hydrophobic arms, larger hydrophilic groups, and higher pKa values and, thus may be less motile than lysine. The hypothesis was tested by guanidination of seven globular proteins (bovine carbonic anhydrase, chymotrypsinogen, alpha-lactalbumin, serum albumin, ribonuclease, hen egg lysozyme, and horse heart cytochrome c). Conversion of lysine residues to homoarginine was between 90 and 99%. Tritium-hydrogen isotope exchange revealed that all proteins except lysozyme demonstrated reduced out-exchange after guanidination. The results with lysozyme were not unexpected since only this protein has a high arginine to lysine ratio. These findings suggest that high arginine to lysine ratios contribute to protein stability.
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PMID:Stabilization of proteins by guanidination. 625 87

Salmo gairdneri specimens were exposed for 4 months to 1-10 micrograms/liter of Cd and 30-100 micrograms/liter of Cu. At different times from the beginning of the experiment the activity of some metal-sensitive enzymes was assayed (blood catalase and carbonic anhydrase; liver aminolevulinate dehydrase and total leucylaminopeptidase ). Biochemical indices of mitochondrial (respiratory control ratio; O2 consumption) and lysosomal function (percentage free leucylaminopeptidase activity), gill sialic acid content, and mucus lysozyme concentration were also detected. Cu (at both the levels tested) and Cd (only at the highest concentration) cause a remarkable alteration in various biochemical/physiological parameters under study. Considerations about the water quality criteria levels proposed by EIFAC /FAO for the two metals are reported.
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PMID:Biochemical effects of long-term exposure to cadmium and copper on rainbow trout (Salmo gairdneri): validation of water quality criteria. 642 36

Sodium oleate cosolubilized with lysozyme in reverse micellar solutions is shown to inhibit the ozone-mediated oxidation of tryptophan residues in the protein. The magnitude of inhibition by oleate, which is an indirect measure of the fraction of ozone that reacts with oleate instead of the protein, is predictable using a kinetic model that is based on the concentrations and the reactivities toward ozone of the amino acid residues in lysozyme and the double bond in oleate. Oleate (2 mM), linoleate (1 mM), linolenate (0.67 mM), and gamma-linolenate (0.67 mM) all inhibit the ozonation of lysozyme similarly; this indicates that ozone reacts with double bonds in mono-, di-, or polyunsaturated fatty acids at approximately the same rate. All these fatty acids reside at the micellar interface with their head groups facing inward toward the dispersed water pools and the hydrocarbon tails projecting into the bulk, continuous organic phase. Various short-chain 2-, 3-, and 4-alkenoic acids that reside predominantly in the water pools, and long-chain alkenes that reside in the bulk organic solvent, have a similar inhibitory effect on the ozone-mediated oxidation of tryptophan residues in lysozyme. Thus, the location of olefinic compounds in the micelles or bulk organic phase per se does not influence the rate of reaction in this reverse micellar system. A number of proteins that reside in the water pools of reverse micelles are found to behave similarly to lysozyme, including albumin, carbonic anhydrase, beta-casein, alpha-chymotrypsin, alpha-lactalbumin, beta-lactoglobulin, papain, apotransferrin, trypsin, and trypsin inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The reactions of ozone with proteins and unsaturated fatty acids in reverse micelles. 815 24


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