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)

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

We have attempted to detect binding of N-acetylglucosamine (NAG) to alpha-lactalbumin, the B protein of lactose synthetase, under conditions in which binding of NAG to lysozyme, a protein to which alpha-lactalbumin has a significant sequence homology, is observed. Using 1H nuclear magnetic resonance spectroscopy, uv difference spectroscopy, competition of NAG with N-methylnicotinamide chloride, and fluorescence spectroscopy, no binding was detected. The synthesis of a NAG analogue, N-diazoacetyl-glucosamine (diazoNAG), was carried out, and the molecule was demonstrated to be an active galactose acceptor in the lactose synthetase reaction. Use of this molecule in photochemical labeling experiments resulted in a large amount of nonspecific labeling of alpha-lactalbumin, lactose synthetase A protein, ribonuclease, and lysozyme, but competition experiments in the presence of an excess of NAG revealed some specific labeling in the case of A protein and lysozyme, but not with alpha-lactalbumin or a ribonuclease control. Thus, it is highly questionable that a NAG binding site is retained in alpha-lactalbumin; furthermore, it appears that the galacyosyl acceptor makes significant contacts with the A protein rather than alpha-lactalbumin in the lactose synthetase complex.
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PMID:The interaction of N-acetylglucosamine and an affinity-label analogue with alpha-lactalbumin and lactose synthetase. 81 Dec 54

A series of bacterial cell wall glycopeptides of low molecular weight and cell wall nucleotide precursors have been tested for their inhibitory action on the digestion by T4 lysozyme of a radioactively labeled linear uncrosslinked peptidoglycan. The disaccharide-peptides GlcNAc-MurNAc-l-Ala-D-Glu(A2pm) (C5) and GlcNAc-MurNAc-L-Ala-D-Glu(A2pm-D-Ala) (C6) as well as the monosaccharide-peptide MurNAc-L-Ala-D-Glu(A2pm) were found to be good competitive inhibitors (with similar Ki values) whereas the disaccharide-pentapeptide GlcNAcMurNAc-L-Ala-DGlu-Gly-L-Lys-D-Ala was a poor inhibitor. T4 lysozyme did not catalyse transglycosylation reactions from Escherichia coli B peptidoglycan to the disaccharide-peptide C6. No changes were seen in the circular dichroism spectra (200-250 nm) or fluorescence emmission spectra upon binding of the good inhibitors. The results obtained indicate that T4 lysozyme has a small active site capable of recognizing a unit consisting of MurNAc-L-Ala-D-Glu(A2pm).
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PMID:The specificity requirements of bacteriophage T4 lysozyme. 94 53

Conformational energy calculations were used to predict the three-dimensional structures of enzyme-substrate and enzyme-inhibitor complexes of lysozyme. A global search method, involving the use of a disaccharide fragment molecule, was used initially to determine all favorable binding regions at the active site. It is shown that the binding of a series of (nonfragmented) oligomers of N-acetylglucosamine is highly specific. The results show further that (a) the enzyme recognizes only one backbone conformation of the oligomer, corresponding to a left-handed helix, and (b) for saccharides containing two or more N-acetylglucosamine residues, two residues bind preferentially to the C and D sites. The calculations also suggest that the chair form of N-acetylglucosamine can bind to the D region. The saccharide residues of tetra-N-acetylglucosamine bind to the A-B-C-D sites, with the residues at the A-B-C sites having essentially the same conformation and orientation as those in the x-ray structure of tetra-N-acetylglucosamine-delta-lactone bound to lysozyme.
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PMID:Prediction of three-dimensional structures of enzyme-substrate and enzyme-inhibitor complexes of lysozyme. 106 81

The binding of 4-(N-acetylaminoglucosyl)-N-acetylglucosamine to lysozyme was studied by both nuclear magnetic resonance (NMR) and temperature-jump methods under comparable conditions. The NMR measurements on the inhibitor spectrum were carried out over a range of inhibitor concentrations including levels at which most of the inhibitor was bound to the enzyme. Data in this region were obtained by a novel difference method in conjunction with correlation spectroscopy. The results from the combination of both experimental techniques demonstrated the existence of a two-step binding mechanism and produced both values for all of the individual rate constants and also the NMR spectral data for the inhibitor in the two enzyme-inhibitor complexes. The later data characterize the environment experienced by the inhibitor at each stage in the binding process and thus provides both a three-dimensional and a dynamic picture of the interaction.
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PMID:The stepwise binding of small molecules to proteins. Nuclear magnetic resonance and temperature jump studies of the binding of 4-(N-acetylaminoglucosyl)-N-acetylglucosamine to lysozyme. 116 93

In order to clarify the state of Trp 62 in hen egg-white lysozyme [EC 3.2.1.17] bound with N-acetylchitooligosaccharides in relation to the ionization states of side chains present in the substrate binding site, the binding of alpha- and beta-N-acetylglucosamine GlcNAc), alpha- and beta-methyl-GlcNAc, (GlcNAc)2, and (GlcNAc)3 was studied by use of the change in the tryptophyl circular dichroic (CD) band at 295 nm at various pH values. The effects of these saccharides on the charge-transfer binding of N-1-methylnicotinamide to Trp 62 were also examined. The binding constants, estimated by use of N-1-methylnicotinamide by assuming noncompetitive binding between the saccharides and N-1-methylnicotinamide, were in good agreement with those determined from the CD change at 295 nm. The state of Trp 62 in saccharide-bound lysozyme was found to depend on the chemical structures of the saccharides and their binding orientations. The relation between the state of Trp 62 and the ionization of the catalytic Glu 35, which is far distant from Trp 62, was also confirmed for lysozyme complexes with various saccharides as well as for free lysozyme.
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PMID:State of Trp 62 in hen egg-white lysozyme bound with N-acetylchitooligosaccharides. 116 35

The influence of urea and of guanidine chloride on the binding of the bacterial substrate and of inhibitors such as N-acetylglucosamine or chitotetraose to hen lysozyme were studied at 20 degrees and at 40 degrees C (physiological temperature). The action of urea did not prevent a certain degree of organization of the enzyme compatible with its usual behaviour in the presence of some inhibitors and with its crystallization ; guanidine chloride, already at low concentrations, seemed to have a more severe effect on lysozyme.
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PMID:The influence of urea and guanidine chloride on the binding of the binding of the bacterial substrate and inhibitors to hen lysozyme at physiological temperature (40 degrees) (*). 124 Dec 84

The functional role of tyrosine-63 in the catalytic action of human lysozyme (EC 3.2.1.17) has been probed by site-directed mutagenesis. In order to identify the role of Tyr63 in the interaction with substrate, both the three-dimensional structures and the enzymatic functions of the mutants, in which Tyr63 was converted to phenylalanine, tryptophan, leucine, or alanine, have been characterized in comparison with those of the wild-type enzyme. X-ray crystallographical analysis of the mutant enzyme at not less than 1.77-A resolution indicated no remarkable change in tertiary structure except the side chain of 63rd residue. The conversion of Tyr63 to Phe or Trp did not change the enzymatic properties against the noncharged substrate (or substrate analogs) largely, while the conversion to Leu or Ala markedly reduced the catalytic activity to a few percent of wild-type enzyme. Kinetic analysis using p-nitrophenyl penta-N-acetyl-beta-(1----4)-chitopentaoside (PNP-(GlcNAc)5) as a substrate revealed that the reduction of activity should mainly be attributed to the reduction of affinity between enzyme and substrate. The apparent contribution of the phenolic hydroxyl group and the phenol group in the side chain of Tyr63 was estimated to 0.4 +/- 0.4 and 2.5 +/- 0.8 kcal mol-1, respectively. The result suggested that the direct contact between the planar side-chain group of Tyr63 and the sugar residue at subsite B is a major determinant of binding specificity toward a electrostatically neutral substrate in the catalytic action of human lysozyme.
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PMID:Dissection of the functional role of structural elements of tyrosine-63 in the catalytic action of human lysozyme. 139 Jul 8

Detailed characterization of enzyme susceptibility of bacterial cellulose containing N-acetylglucosamine (GlcNAc) residues (N-AcGBC) which possess high susceptibility for cellulase and lysozyme and slight susceptibility for chitinase was studied. Turbidimetric lysozyme assay of N-AcGBC showed that (i) the susceptibilities of various N-AcGBCs for lysozyme were proportional to GlcNAc content, and (ii) N-AcGBC homogenates were divided into two groups based on the rate of turbidity reduction (not dependent on GlcNAc content). High reactivity of N-AcGBC for lysozyme would arise from fine microfibrils characteristic of bacterial cellulose (BC) and random distribution of GlcNAc residues in N-AcGBC because water soluble oligomers of N-AcGBC produced by lysozymic hydrolysis did not inhibit lysozyme activity; however, the random distribution of GlcNAc seemed to result in the slight susceptibility of N-AcGBC for chitinase. The rate of cellulolytic turbidity reduction of N-AcGBC was slower than that of BC, which arose from the inhibition for binding of cellulase by GlcNAc residues.
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PMID:Susceptibilities of bacterial cellulose containing N-acetylglucosamine residues for cellulolytic and chitinolytic enzymes. 147 90

The pressure-induced reversible unfolding of lysozyme was investigated by high-resolution proton magnetic resonance spectroscopy by following the proton spectra of the following residues: His-15 epsilon 1, Trp-28 epsilon 3, Leu-17 delta 2, Cys-64 alpha, and Trp-108 epsilon 3. The experiments were performed at pH 3.9 and 68.5 degrees C in the pressure range from 1 bar to 5 kbar both in the absence and presence of tri-N-acetylglucosamine (tri-NAG). From the pressure-induced changes of the equilibrium between the native and denatured forms of lysozyme, the reaction volumes (delta V) were calculated for each residue. Small but statistically significant differences in delta V were found for residues located in different regions of the protein. For example, delta V for the disulfide bonded Cys-64 alpha is smaller than the delta V's found for the other residues. In particular, the effect of tri-NAG binding to lysozyme was a change of delta V from -10.3 +/- 0.6 cm3/mol to -18.1 +/- 1.7 cm3/mol for the Trp-108 epsilon 3 residue which is located close to the active site. It is important to note that the Cys-64 alpha residue also senses the binding of the substrate analog. The ability to detect statistically significant differences for delta V of individual residues located in different regions of lysozyme represents the main result of these experiments.
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PMID:High-resolution NMR study of the pressure-induced unfolding of lysozyme. 151 Sep 63


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