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)

Ultraviolet difference absorption spectra produced by ethylene glycol were measured for hen lysozyme [EC 3.2.1.17] and bovine chymotrypsinogen. N-Acetyl-L-tryptophanamide and N-acetyl-L-tyrosinamide were employed as model compounds for tryptophyl and tyrosyl residues, respectively, and their ultraviolet difference spectra were also measured as a function of ethylene glycol concentration. By comparison of the slopes of plots of molar difference extinction coefficients (delta epsilon) versus ethylene glycol concentration for the proteins with those of the model compounds at peak positions (291-293 and 284-287 nm) in the difference spectra, the average number of tyrosyl as well as tryptophyl residues in exposed states could be estimated. The results gave 2.7 tryptophyl and 1.9 tyrosyl residues exposed for lysozyme at pH 2.1 and 2.6 tryptophyl and 3.4 tyrosyl residues exposed for chymotrypsinogen at pH 5.4. The somewhat higher tyrosyl exposure of chymotrypsinogen, compared with the findings from spectrophotometric titration and chemical modification, was not unexpected, because delta epsilon285 was larger than delta epsilon292, and the situation is discussed with reference to preferential interaction of ethylene glycol with the tyrosyl residues and/or side chains in the vicinity of the chromophore in the protein. The procedure employed in the present work seems to be suitable for estimation of the average number of exposed tryptophyl and tyrosyl residues in tryptophan-rich proteins. The effects of ethylene glycol on the circular dichroism spectra of lysozyme at pH 2.1 and chymotrypsinogen at pH 5.4 were also investigated. At high ethylene glycol concentrations, both proteins were found to undergo conformational changes in the direction of more ordered structures, presumably more helical for lysozyme and more beta-structured for chymotrypsinogen.
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PMID:Estimation of tryptophyl and tyrosyl exposure in tryptophan-rich proteins by ultraviolet difference spectrophotometry. Lysozyme and Chymotrypsinogen. 0 42

Staphylococcus epidermidis peptidoglycans solubilized by sonication or lysozyme digestion, and synthetic peptidoglycan analogs such as HSA-carboxymethyl-Gly-L-Ala-L-Ala-D-Ala-D-Ala (HSA-pentapeptide) or L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala (pentapeptide) have been labeled with 125I and tested for their applicability in the radioactive antigen binding assay. Use of radioiodinated Staph. epidermidis peptidoglycans was found to be considerably impeded by the presence of at least 2 different antigenic sites on such molecules, the pentapeptide and the glycan determinant. Application of labeled HSA-pentapeptide was limited by the necessity to use PEG for precipitation of Ag-Ab-complexes and by short linear potions of binding curves. However, the synthetic pentapeptide hapten, radioiodinated by the active ester method of BOLTON and HUNTER, proved to be a most useful regent for the selective measurement of pentapeptide antibody. Inhibition studies indicated that the immunological specificity of the labeled hapten was retained. Pentapeptide binding curves were linear from 15-500 g/ml of antibody. Generally, there was good agreement between pentapeptide antibody concentrations measured by radioimmunoassay and quantitative precipitation.
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PMID:Measurement of peptidoglycan antibodies by a radioimmunoassay. 5 37

Normal fresh and heat-inactivated (56 degrees C, 30 min) human sera (80 vol%, i.e., 80% [vol/vol] of a 2-ml assay volume) killed Bacillus subtilis ATCC 6633 cell inocula of 1.5 x 10(4) colony-forming units per ml within 1 to 2 h after exposure. The B. subtilis assay strain proved slightly and reversibly susceptible to 5 mug of egg white lysozyme per ml. Seitz filtration of fresh human serum completely removed beta-lysin activity; significant amounts of serum lysozyme were removed as well, as determined with the bioassay strain Micrococcus lysodeikticus ATCC 4698. However, bactericidal activity of human serum via classical or alternative complement pathway activation remained intact. Addition of 0.01 M dithiothreitol to fresh human serum abolished beta-lysin activity, but not that of serum lysozyme. Chelation of fresh and heat-inactivated human serum with 0.01 M MgCl(2) + 0.01 M ethylene glycol tetraacetic acid, but not with 0.01 M ethylenediaminetetraacetic acid, markedly retarded beta-lysin activity; however, lysozyme activity remained unaffected. Chelation of serum with 0.01 M MgCl(2) + 0.01 M ethylene glycol tetraacetic acid + 0.01 M CaCl(2) completely abrogated beta-lysin activity, but not that of lysozyme. Absorption of human serum with 10 mg of bentonite per ml (10 min, 37 degrees C) completely removed beta-lysin and lysozyme activity, but failed to affect serum bactericidal activity against Escherichia coli control strain C. Reconstitution of 50 vol% of bentonite-absorbed serum with 40 vol% of heat-inactivated human serum restored both beta-lysin and lysozyme activity. Addition of either 63 to 500 mug of sodium polyanetholsulfonate per ml or 63 to 500 mug of sodium amylosulfate per ml to 80 vol% of fresh human serum completely neutralized beta-lysin activity for the entire observation period of 22 h.
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PMID:Neutralization of human serum beta-lysin by sodium polyanetholsulfonate and sodium amylosulfate. 22 18

The chemical modification of tryptophan residues of hen egg-white lysozyme by N-bromosuccinimide (NBS) was studied kinetically by the stopped-flow method, monitoring changes in absorbance and fluorescence. One most rapidly reacting tryptophan residue, probably Trp 62, was clearly distinguished from four other residues in terms of rate of modification. This residue was protected by ethylene glycol chitin, N-acetyl glucosamine (NAG), and tri-NAG, but not by gluconolactone. The dissociation constant Kd of the enzyme-ligand complex was obtained from the protection effects. These results are in good agreement with results previously obtained.
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PMID:Kinetic studies on the chemical modification of lysozyme by N-bromosuccinimide and its protection by substrates and analogs. 89 64

In vitro deoxyribonucleic acid (DNA) synthesis systems based on an earlier system using pencillin have been developed which use osmotic lysis of lysozyme-formed spheroplasts of Escherichia coli cells embedded in an agarose matrix. An adenosine 5'-triphosphate (ATP)-dependent semiconservative mode, or replicative mode, of in vitro DNA synthesis is exhibited which is sensitivie to nalidixic acid. These systems require growth of the agar-embedded cells in a preincubation medium before spheroplast formation and osmotic lysis. Inhibitor studies suggest that one or more required macromolecular species are synthesized during this preincubation growth period. Osmotic shock fluid from E. coli contains macromolecular factors which preferentially stimulate the ATP- dependent semiconservative mode of in vitro DNA synthesis. In some cases, the ATP independent mode of synthesis is inhibited by shock fluid. Evidence is presented that the stimulating factors found in the osmotic shock fluid come from the E. coli periplasmic space. This stimulation is observed using either toluene-treated cells or lysed agar-embedded ethylene glycol-bis-(beta-aminoethyl ether) N,N'-tetraacetate-lysozyme spheroplasts, and is thus independent of the in vitro DNA synthesis system used. Shock fluid obtained from a given E. coli dna mutant does not stimulate in vitro DNA synthesis by that mutant. However, in some cases, shock fluid from one class of dna mutants does stimulate ATP dependent in vitro DNA synthesis by another class of dna mutants, in a thermosensitive reacaction. Gently prepared cell extracts also stimulate ATP-dependent in vitro DNA synthesis, whereas cell extracts prepared by more severe procedures inhibit this in vitro synthesis. Severl stimulating DNA replication factors may be present in the osmotic shock fluid, including products of E. coli dna genes.
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PMID:Stimulation of adenosine 5'-triphosphate-dependent in vitro deoxyribonucleic acid replication by factors from the periplasmic space of Escherichia coli. 109 20

A quick, simple protocol is described for the preparation of tissue for electron immunocytochemistry without the use of fixatives or deleterious solvents. Fresh, normal human colon was rapidly dehydrated in ethanediol (ethylene glycol) then embedded directly in low-acid glycol methacrylate. Using both mono- and polyclonal antibodies, in conjunction with colloidal gold probes, a range of intra- and extracellular epitopes were localized; these epitopes included lysozyme, chromogranin, desmin and collagen IV. Overall, the tissue compared well with material fixed in glutaraldehyde, partially dehydrated and embedded in LR White acrylic resin. Ultrastructural detail was good and was further enhanced, without affecting probe density and epitope localization, by the addition of 1% tannic acid or 1% uranyl acetate to the dehydrant. The technique is applicable to a wide range of tissues, allowing excellent antigen retention which might prove useful for the immunolocalization of sensitive epitopes.
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PMID:Unfixed tissue for electron immunocytochemistry: a simple preparation method for colloidal gold localization of sensitive epitopes using ethanediol dehydration. 137 8

The amino groups of hen egg white lysozyme were reductively alkylated by the reaction with aliphatic aldehydes of various chain lengths and with two aldehydes of different steric hindrance at pH 7.5 and 4 degrees for 3 h. About four of the original six lysine residues were modified by the reaction with acetaldehyde, n-butylaldehyde or n-hexylaldehyde. About three lysine residues were 2,2-dimethylpropylated with trimethylacetaldehyde while a single residue was modified with benzaldehyde. The thermal stabilities of these alkylated lysozymes were investigated by differential scanning calorimetry (DSC) at different acidic pH values. Alkylation thermally destabilized the proteins, depending not only on the extent of modification but also on the size of the substituent. The alkylated derivatives were 8-19 kJ/mol less stable than native lysozyme at 25 degrees and pH 3.0. The temperature dependences of the activities of the alkylated lysozymes against ethylene glycol chitin indicated that the orders of the optimum temperatures and the maximum activities were exactly the same as the order of the thermal stabilities.
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PMID:Effect of alkylation with different sized substituents on thermal stability of lysozyme. 144 66

Chitinase has been purified from the extract of cabbage through successive steps of ammonium sulfate fractionation, chromatofocusing and Sephadex G-75 gel filtration. By these steps, the purity of the enzyme increased by 93.3 fold and the recovery of the enzyme activity was 20%. The purified enzyme had an optimal pH of 5.0, an optimal temperature between 40 to 50 degrees C and a Km of 76 microM for hydrolysis of ethylene glycol chitin. The molecular weight of the enzyme determined from filtration through Sephadex G-75 was 30,000 daltons. Heavy metal ions, Hg2+ (0.5 mM) and Ag+(2.5 mM) significantly inhibited the activity of the enzyme. NBSI1 (1.0 mM), DNFB (0.5 mM) and PMSF (0.5 mM) completely inhibited the activity of the enzyme. The enzyme also showed muramidase activity for hydrolysis of Micrococcus lysodeikticus cell wall. The presence of chitinase in cabbage may function as a defense enzyme against potential pathogens.
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PMID:Purification and properties of chitinase from cabbage. 148 7

A nonionic, high-water-content, high-strength hydrogel based on N-vinyl pyrrolidinone (NVP) and a novel hydrophilic-bulky monomer, 4-t-butyl-2-hydroxycyclohexylmethacrylate (TBCM), was developed. The TBCM was prepared in three relatively simple, high-yield steps. The copolymerization of NVP with varying concentrations of TBCM resulted in transparent hydrogel films possessing a wide range in mechanical and physical properties. A copolymer composition of 91.7 parts NVP, 8.0 parts TBCM, and 0.3 parts ethylene glycol dimethacrylate (EGDMA) gave a transparent, flexible film possessing a water content of 86%, a modulus of 130 g/mm2, and a tear strength of 3.4 g/mm. In contrast, a copolymer composition of 49.7 parts NVP, 50 parts TBCM, and 0.3 parts EGDMA gave a transparent, hard hydrogel film possessing a water content of 26% and a modulus of 86,000 g/mm2. All of the high-water copolymer compositions developed resulted in lysozyme uptake typical of nonionic high-water-content hydrogels and oxygen permeability levels greater than 50 (cm3-O2(STP).cm)/(s.cm2.mm Hg) x 10(-11).
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PMID:High-strength hydrogels based on N-vinyl pyrrolidinone and 4-t-butyl-2-hydroxycyclohexylmethacrylate. 157 35

When reactions take place with one of the reactants tied to protein matrix, movements along the reaction coordinate towards the transition state can become coupled to structural fluctuations of the protein matrix. This investigation aims to test the assumptions underlying the arguments supporting such a coupling. A coupling is allowed only if the activation barrier is high and broad enough as shown to be the case for the proton catalyzed isotope exchange at Trp-63 of lysozyme. In the present investigation the activation barrier for the same reaction has been lowered radically in an effort to show that the coupling, as measured by the dependence of rate on solution viscosity, will diminish and ideally vanish, despite the unchanged effects of cosolvents on the chemical activities of all the reactants. The isotope exchange rate at the indole nitrogen of the single tryptophan residue of human serum albumin was measured with UV. This residue is rigidly held to the protein surface and the solvent access, although restricted, corresponds to a partially exposed residue. As a consequence, the isotope exchange rates and the bimolecular quenching rate of fluorescence by acrylamide, also measured, are high. The experiments were carried out at pH 5.2 where the molecule is in the N-form and the exchange is catalyzed by OH- ions. The activation energy of the hydroxyl catalyzed reaction is 22 kJ lower than for the proton catalyzed process. Under these conditions the exchange rate is viscosity independent both in the case of glycerol and in ethylene glycol.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The effect of viscosity on the accessibility of the single tryptophan in human serum albumin. 158 18


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