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)

Autoxidized LA is classified into four groups, LA, LAHPO, SP and FP. Lysozyme is inactivated by these products in the increasing order as follows: FP less than LA less than LAHPO less than SP. The effects of these products on the amino acid composition of lysozyme is examined. All kinds of amino acid residues were not damaged until lysozyme was incubated with LA and LAHPO at 45 degrees C for 100 days. The susceptible amino acid residues attacked by the autoxidized products are tryptophan, lysine and histidine. The specific loss of methionine by SP occurs during acid-hydrolysis. The effect of SP was the strongest among the autoxidized products. FP was almost noneffective. The destructive actions of BP, MA and PA were compared with those of autoxidized products. Effects of these compounds did not resemble those of autoxidized products. It was concluded that tryptophan, lysine and histidine residues were specifically attacked by SP.
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PMID:Lysozyme damage caused by secondary degradation products during the autoxidation process of linoleic acid. 0 40

The chemical modification of lysozyme (I) has been accomplished with alpha, alpha'-dibromo-p-xylenesulfonic acid (DBX) at five different pH values. I was alkylated by DBX at room temperature (28 degrees C) with decrease in enzyme activity. The rate of inactivation depended upon the pH at which alkylation was carried out. The highest rate was seen at alkaline pH values; the lowest at more acidic pH values. Amino acid analyses showed that-two lysines and two tryptophan residues had been modified at pH 9; two lysines, one tryptophan and one methionine had reacted at pH 8. A histidine residue was bound at pH 6.5 together with a tryptophan residue. At the lower pH values (2.7, 4.5, 6.5), alkylation occurred with a single tryptophan residue each. Fluorescence and CD data both ruled out the participation of tryptophans 62 or 108. Labeling experiments showed that two residues of DBX-35S were bound per molecule of I at both pH9 and pH8; one residue of DBX was bound per molecule of I at the other pH values. Sedimentation coefficients were characteristic of native lysozyme. The stoichiometry of binding and residue modification indicated that intra-molecular cross links were established. The pH dependence of the cross-linking provides means to measure several allowed intra-molecular distances. The results presented here are consistent with the existence of side chain motion in lysozyme.
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PMID:The pH dependence of binding of alpha,alpha'-dibromo-p-xylenesulfonic acid to lysozyme. 0 99

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

1. Lysozyme from eggs of the Dipterous Ceratitis capitata (Wiedeman) has been purified by ion-exchange chromatography and gel filtration and its physicochemical properties have been investigated. This is the first insect lysozyme characterized so far and it exhibits some properties different to those described for other animal lysozymes. 2. Lysozyme from the insect eggs has a molecular weight of about 23200 and a sedimentation coefficient of 2.4 S. Molecular weight determination by sodium dedecylsulphate gel electrophoresis indicates that the molecule consists of a single polypeptide chain. 3. This lysozyme preparation shows notable stability at acidic pH values and lability at alkline pH values. It shows a single optimum pH at about 6.5.4. Chitinase/muramidase specific activity ratio is around 350 times higher for the insect lysozyme than for the hen egg-white enzyme. 5. The amino-acid composition shows the presence of one tryptophan residue per molecule of enzyme. This fact differentiates the lysozyme from insect eggs from other animal and plant lysozymes. From the amino acid composition, the absorption coefficient and the partial specific volume are calculated. 6. Glycine is the N-terminal residue.
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PMID:Lysozyme from the insect Ceratitis capitata eggs. 1 78

Chemical studies of selective modification of Trp-108 of lysozyme gave ambiguous results concerning its function on the catalytic activity, since the oxyndole derivative obtained with N-bromosuccinimide is inactive, whereas the kynurenine derivative obtained by oxidation with ozone is fully active. In order to explain this discrepancy, lysozyme has been modified with 2-nitro-4-carboxyphenylsulfenyl chloride (NCPS-Cl). This reagent reacts with the indole ring of tryptophan giving a 2-thioaryl-derivative. By chromatographic fractionation of the reaction mixture, a lysozyme derivative was isolated, that by sequence studies was proved to be modified only at Trp-108 retaining 10% of the lytic activity. Physico-chemical as well as kinetic studies indicate that the large decrease in activity following modification could be related to minor effects in the microenvironment of the active site, with a concomitant modification of the ionization constants of the groups involved in catalysis.
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PMID:Studies on the function of tryptophan-108 on lysozyme. 2 61

The identification and complete assignment of the C-2 and N-1 proton nuclear magnetic resonances (NMR) of the six tryptophan residues of hen lysozyme are reported. Identification of the resonances required a detailed examination of the spectra of the protein in H2O and in 2H2O, and involved the application of spin-echo and Carr-Purcell-Meiboom-Gill pulse sequences. Assignment was achieved by observing the effects on the NMR spectra of performing specific chemical modifications, of binding paramagnetic species (lanthanide ions and spin labels), of binding inhibitors and protons and of carrying out solvent exchange experiments. The problems involved in completion of assignment are fully discussed. In the course of performing experiments to make assignments, several interesting aspects of the behaviour of the tryptophan residues in the protein structure were observed and are discussed.
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PMID:Study of the tryptophan residues of lysozyme using 1H nuclear magnetic resonance. 3 40

The alterations of tryptophan fluorescence parametres with pH may be due to: 1) conformational changes; 2) changes in the ionic state of groups capable of quenching the tryptophan fluorescence. The applications of the model of discrete forms of tryptophan allow one to separate these mechanisms and estimate the middle points of conformational changes and pK's of quenching groups. For chymotrypsin (CT) and chymotrypsinogen (CTG) conformational changes were registrated with middle points: CT pH 4.1 and 8.8; CTG -- pH 3.2 and 9.8, and pK's of histidines: CT -- 5.4 and 6.6; CTG -- 5.6 and 7.0. For trypsin conformational changes were shown with middle points: pH 3.2; 5.8; 8.5 and for lysozyme -- pH 5.9.
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PMID:[pH-dependence of fluorescence parameters of chymotrypsin, chymotrypsinogen, trypsin and lysozyme]. 3 49

A novel method for the preparation of Kyn 62-lysozyme, in which tryptophan 62 is replaced by kynurenine, is reported. Hen egg-white lysozyme was ozonized in aqueous solution to yield one N'-formylkynurenine residue and deformylated with hydrochloric acid in frozen solution at -10 degrees C. Crude Kyn 62-lysozyme was purified by affinity and Bio Rex 70 chromatography successively. Kyn 62-lysozyme retains affinity for chitin and is essentially an active enzyme with a slightly weakened but distinct catalytic activity. After this modification, the enzyme activity was changed differently depending on the kind of substrate. At the individual optimum pH's, lytic activity was largely retained (80% active), but the catalytic efficiency for hydrolyzing glycol chitin was relatively low (30% active). Lysis of M. lysodeikticus cell suspensions was optimally catalyzed by Kyn 62-lysozyme at pH 6.2 and at 0.088 ionic strength. These values are lower by 1.3 pH unit and 0.04 ionic strength, respectively, than those of intact lysozyme. The optimum pH and ionic strength for the hydrolysis of neutral substrates were scarcely affected. These results suggest the significance of electrostatic interaction in the lysis of lysozyme. Relatively limited loss of activity induced by modification of the 62nd residue, which is thought to participate directly in the binding of the substrate at subsite C, is discussed on the basis of the similarity of side chain structure in tryptophan and kynurenine.
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PMID:Preparation and characterization of an active lysozyme derivative: Kyn 62-lysozyme. 4 44

Previous studies from this laboratory on the immunochemistry of specific chemical derivatives of native lysozyme and of the two disulfide peptide 62-68 (Cys 64-Cys 80) 74-97 (Cys 76-Cys 94) (i.e. (SS)2-peptide), have established an antigenic reactive site to comprise the spatially contiguous surface residues: Trp 72, Lys 97, Lys 96, Asn 93, Thr 89 and Asp 87. In the present work, the identity of the site was verified by an entirely different and novel approach. The aforementioned amino acids were linked directly into a single linear peptide with an intervening spacer where appropriate and substituting phenylalanine for tryptophan (i.e. Phe-Gly-Lys-Asn-Thr-Asp). This peptide (which does not exist in native lysozyme but simulates a surface region of the protein) possessed a remarkable inhibitory activity towards the reaction of lysozyme with its antisera. The immunochemical reactivity of the peptide was equal to the maximum expected reactivity of the site (i.e. a third of the total antigenic reactivity of lysozyme). These findings define quite conclusively and accurately the reactive site which is clearly composed of spatially adjacent residues that are distant in sequence reacting as if in direct linear linkage. The unequivocal establishment of this concept indicates that antigenic sites need not always be composed of residues in direct peptide linkage in the sequence. The nature of the site may depend on the protein. This unorthodox attack at the problem provides a novel and powerful approach for final delineation of the antigenic reactive sites (and perhaps other types of binding sites) in native proteins, following the completion of accurate narrowing down by chemical methods.
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PMID:Enzymic and immunochemical properties of lysozyme. XVI. A novel synthetic approach to an antigenic reactive site by direct linkage of the relevant conformationally adjacent residues constituting the site. 5 5

In order to probe the cause and nature of conformational changes induced by the chemical modification of amino groups in proteins, five acylated derivatives of ovalbumin namely 21% acetylated, 32% succinylated, 90% butyrated 92% succinylated, and 95% acetylated ovalbumins were prepared and their molecular and immunological properties were systematically investigated. As evidenced by the ultraviolet difference spectral, solvent perturbation, gel filtration, and viscosity data, acylation of the amino groups produced a definite conformational change in native ovalbumin whose extent was higher for higher degrees of chemical modification. The solvent pertubation data showed an exposure of 0.5 tryptophan and 3 tyrosine residues in native ovalbumin; the exposure increased to 1 tryptophan and about 5 tyrosine residues in the maximally modified proteins (i.e. 90% butyrated, 92% succinylated, and 95% acetylated ovalbumins). The Stokes radius (2.7 nm) and intrinsic viscosity (3.9 ml/g) of ovalbumin increased, respectively, to about 3.4 nm and 7.7 ml/g upon acylation of its 18 lysine residues; the intrinsic viscosity of 95% acetylated ovalbumin was 7.2 ml/g. The reduced viscosity of ovalbumin (4.2 ml/g) which remained unaltered on raising the pH to pH 11.2, increased to 7.9 ml/g on succinylation of 18 lysine residues. On raising the ionic strength from 0.15 to 1.0, the value decreased from 7.9 to 6.2 ml/g. These observations taken together with the fact that the intrinsic viscosities of 92% succinylated and 90% butyrated ovalbumins are identical, argue against the presently prevalent proposal that electrostatic effects alone are responsible for the disruption of native protein conformation during chemical modification. The immunological activity of ovalbumin towards rabbit anti-ovalbumin expectedly decreased with acylation of its amino groups but the three maximally modified ovalbumins retained 40% immunological activity. This taken along with the spectral and viscosity data showed substantial native structure (format) in the three maximally acylated derivatives. The rabbit antiserum against 95% acetylated ovalbumin did not cross-react with acetylated lysozyme and reacted poorly with the native and 92% succinylated ovalbumins suggesting that the antigenic make-up of the three maximally modified ovalbumins is different.
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PMID:Changes in conformation and immunological activity of ovalbumin during its modification with different acid anhydrides. 10 Dec 49


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