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)

A lysozyme-catalyzed reaction is initiated by a cleavage of the beta-1, 4-glucosaminide linkage, followed by hydration and transglycosylation. Since all glycosides produced by transglycosylation have beta-glycosidic linkages between the sugar and the acceptor moieties, the lysozyme-catalyzed reaction has been classified as an anomer-retention reaction. However, there is no experimental evidence on the anomer retention of the new reducing residue produced by the hydrolysis of the substrate. In the present study, an attempt was made to determine the anomeric form of the GlcNAc residue at the reducing end in nascent hydrolytic products. The anomeric forms of the enzymatic products were separated and quantitatively analyzed by high-performance liquid chromatography. The amounts of alpha- and beta-anomers in the product were plotted against the reaction time. Computer analysis of the experimental data indicated that the nascent hydrolytic product takes only the beta-anomeric form and that the alpha-anomer is formed from beta-anomer by mutarotation.
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PMID:Retention of anomeric form in lysozyme-catalyzed reaction. 381 61

The structure of the linkage unit between ribitol teichoic acid and peptidoglycan in the cell walls of Listeria monocytogenes EGD was studied. A teichoic-acid--glycopeptide preparation isolated from lysozyme digests of the cell walls of this strain contained mannosamine, glycerol, glucose and muramic acid 6-phosphate in an approximate molar ratio of 1:1:2:1, together with large amounts of glucosamine and other components of teichoic acid and glycopeptides. A teichoic-acid-linked sugar preparation, obtained by heating the cell walls at pH 2.5, also contained glucosamine, mannosamine, glycerol and glucose in an approximate molar ratio of 25:1:1:2. Part of the glucosamine residues were shown to be involved in the linkage unit. Thus, on mild alkaline hydrolysis, the teichoic-acid-linked sugar preparation gave a disaccharide characterized as N-acetylmannosaminyl(beta 1----4)-N-acetylglucosamine [ManNAc(beta 1----4)GlcNAc] in addition to the ribitol teichoic acid moiety, whereas the teichoic-acid - glycopeptide was separated into disaccharide-linked glycopeptide and the ribitol teichoic acid moiety by the same procedure. Furthermore, Smith degradation of the cell walls gave a characteristic fragment, EtO2-P-Glc(beta 1----3)Glc(beta 1----1/3)Gro-P-ManNAc(beta 1----4)GlcNAc (where EtO2 = 1,2-ethylenediol and Gro = glycerol). The results lead to the conclusion that in the cell walls of this organism, the ribitol teichoic acid chain is linked to peptidoglycan through a novel linkage unit, Glc(beta 1----3)Glc(beta 1----1/3)Gro-P-(3/4)ManNAc-(beta 1----4)GlcNAc.
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PMID:Characterization of a novel linkage unit between ribitol teichoic acid and peptidoglycan in Listeria monocytogenes cell walls. 391 62

The effect of O-(carboxymethyl)chitins (CM-chitins) on the activation of mouse-peritoneal macrophages in vivo and their mitogenic activity on mouse spleen-cells were investigated. The induction of cytotoxic macrophages is enhanced by an increase of negative charge at O-6 and decreased by further modification at O-3 of the GlcNAc residue. CM-Chitins had a minor effect on mitogenic activity that was independent of the site of modification; partially N-deacetylated chitins had little activity. Although there was remarkable enhancement of accessibility to lysozyme upon modification at O-6 of the GlcNAc residue, the accessibility was decreased by further substitution at O-3.
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PMID:Bioactive chitin derivatives. Activation of mouse-peritoneal macrophages by O-(carboxymethyl)chitins. 395 76

The trifluoroethanol-induced unfolding of hen egg-white lysozyme was studied by circular dichroism. It was shown that if the H2O/trifluoroethanol ratio is above 10:1 (v/v), the unique three-dimensional structure of the protein is not affected, whereas within the ration 10:1-2.8:1 (v/v), this structure is partially unfolded. At the ratio 2.4:1 (v/v), the native conformation of lysozyme is completely disrupted and the conformational transition fits a two-state model. A similar effect was observed for the trifluoroethanol-induced unfolding of the lysozyme-(GlcNAc)3 complex. Within the H2O2 trifluoroethanol ratio 15:1-5.5:1 (v/v), the characteristic intensities of the Cotton effects which arise from the association of (GlcNAc)3 with the active site of lysozyme, diminished and approached those exhibited by lysozyme itself at the same H2O trifluoroethanol ratios. This shows that (GlcNAc)3 is released from the protein surface in early stages of the unfolding process. At the ratio 2.4:1 (v/v), the lysozyme-(GlcNAc)3 complex was completely disrupted and the protein unfolded. It is suggested that a considerable alteration in hydration of the lysozyme molecule caused by trifluoroethanol increases protein surface fluctuations, causing the release of (GlcNAc)3 from the active site of lysozyme.
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PMID:Early stages in the trifluoroethanol-induced unfolding of hen egg-white lysozyme and its complex with (GlcNAc)3. 397 Sep 38

Structural studies were carried out on the linkage units in the teichoic-acid--glycopeptide complexes isolated from lysozyme digests of the cell walls of Bacillus coagulans AHU 1366. On treatment with 47% hydrogen fluoride, the complexes gave a disaccharide characterized as glucosyl(beta 1----4)N-acetylglucosamine together with major fragments, galactosyl(alpha 1----2)glycerol. By means of Smith degradation and partial acid hydrolysis, the teichoic acid chain was shown to be composed of the repeating units, galactosyl(alpha 1----2)glycerol-3(1)-phosphate, which were joined by phosphodiester bonds at C-6 of the galactose residues. The mild alkaline hydrolysis of teichoic-acid-linked glycan fragments yielded teichoic acid chains and disaccharide-linked glycan fragments, from which the disaccharide, glucosyl(beta 1----4)N-acetylglucosamine, was liberated by mild acid hydrolysis, whereas the same disaccharide linked to the teichoic acid chain was obtained by direct heating of the cell walls at pH 2.5. In addition, the presence of specialized glycerol phosphate units in the linkage region was shown by the isolation of tris(glycerol phosphate)3-glucosyl(beta 1----4)N-acetylglucosamine from the products of the Smith degradation of the teichoic-acid--glycopeptide complexes. Thus, it is concluded that the poly(galactosylglycerol phosphate) chain in the cell walls of B. coagulans AHU 1366 is linked to peptidoglycan through a novel linkage unit, bis(glycerol phosphate)-3-glucosyl(beta 1----4)N-acetylglucosamine.
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PMID:Structural studies on the linkage unit between poly(galactosylglycerol phosphate) and peptidoglycan in cell walls of Bacillus coagulans. 397 75

Structural studies were carried out on the polymer chains and their linkage regions in two kinds of teichoic acids, poly(N-acetylglucosamine 1-phosphate) [poly(GlcNAc-1-P)] and glycerol teichoic acid, bound to peptidoglycan in the cell walls of Bacillus pumilus AHU 1650. The poly(GlcNAc-1-P)-glycan complex isolated from lysozyme digests of the cell walls contained mannosamine and glycerol as minor components. On the basis of proton NMR spectroscopic data and isolation of N-acetylglucosamine 4-phosphate from acid hydrolysates, the poly(GlcNAc-1-P) was shown to be a polymer in which N-acetylglucosamine 1-phosphate units are joined at C-4 of the glucosamine residues. Mild alkaline hydrolysis of the poly(GlcNAc-1-P)-glycan complex gave a mannosamine-linked glycan fragment and the acidic polymer fraction that contained glycerol residues. Mild acid treatment of the mannosamine-linked glycan fragment gave the linkage disaccharide, ManNAc(beta 1----4)GlcNAc, whereas the acidic polymer fraction was degraded by this treatment into N-acetylglucosamine 4-phosphate and a glycerol-containing fragment characterized as P-(Gro-P)7 (Gro = glycerol). On the other hand, direct mild acid hydrolysis of the complex gave a fragment characterized as P-(Gro-P)7-ManNAc(beta 1----4)GlcNAc. These results lead to a conclusion that in the cell walls the poly(GlcNAc-1-P) chain is attached to peptidoglycan through a linkage unit, (Gro-P)7-ManNAc(beta 1----4)GlcNAc. By means of similar procedures, it was shown that the other cell wall polymer, glycerol teichoic acid, is also attached to peptidoglycan through the same disaccharide, ManNAc(beta 1----4)GlcNAc.
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PMID:Structural studies on the linkage unit between poly(N-acetylglucosamine 1-phosphate) and peptidoglycan in cell walls of Bacillus pumilus AHU 1650. 399 10

Teichoic acid-glycopeptide complexes were isolated from lysozyme digests of the cell walls of Bacillus coagulans AHU 1631, AHU 1634, and AHU 1638, and the structure of the teichoic acid moieties and their linkage regions was studied. On treatment with hydrogen fluoride, each of the complexes gave a hexosamine-containing disaccharide, which was identified to be glucosyl(beta 1----4)N-acetylglucosamine, in addition to dephosphorylated repeating units of the teichoic acids, namely, galactosyl(alpha 1----2)glycerol and either galactosyl(alpha 1----2)[glucosyl(alpha 1----1/3)]glycerol (AHU 1638) or galactosyl(alpha 1----2)[glucosyl(beta 1----1/3)]glycerol (AHU 1631 and AHU 1634). From the results of Smith degradation, methylation analysis, and partial acid hydrolysis, the teichoic acids from these strains seem to have the same backbone chains composed of galactosyl(alpha 1----2)glycerol phosphate units joined by phosphodiester bonds at C-6 of the galactose residues. The presence of the disaccharide, glucosyl(beta 1----4)N-acetylglucosamine, in the linkage regions between teichoic acids and peptidoglycan was confirmed by the isolation of a disaccharide-linked glycopeptide fragment from each complex after treatment with mild alkali and of a teichoic acid-linked saccharide from each cell wall preparation after treatment with mild acid. Thus, it is concluded that despite structural differences in the glycosidic branches, the teichoic acids in the cell walls of the three strains are linked to peptidoglycan through a common linkage saccharide, glucosyl (beta 1----4) N-acetylglucosamine.
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PMID:A common linkage saccharide unit between teichoic acids and peptidoglycan in cell walls of Bacillus coagulans. 403 Jul 16

Hen egg-white lysozyme (EC 3.2.1.17) was specifically esterified at aspartic acid 52 by the affinity labeling reagent 2',3'-epoxypropyl beta-glycoside of di-(N-acetyl-D-glucosamine) [Eshdat et al. (1973) J. Biol. Chem.248, 5892]. The disulfide bonds of the affinity-labeled enzyme and the aspartic acid 52-ester bond were reduced with dithiothreitol and sodium borohydride, respectively, resulting in the removal of the affinity label. The reduced protein contained 0.9 mole of homoserine and 1 mole less of aspartic acid per mole of protein, as compared to the native enzyme. It was reoxidized by a mixture of reduced and oxidized glutathione to yield a modified protein that possessed one-tenth of the activity of native lysozyme (presumably due to a contamination by regenerated lysozyme formed as a result of hydrolysis of the aspartic acid 52-ester bond during the chemical treatment). The native enzyme, after reduction and reoxidation in the same manner, retained its amino-acid composition, full enzymatic activity, and fluorescence properties. The modified lysozyme, containing homoserine 52, showed the same fluorescence spectrum as the native enzyme. With both proteins, the fluorescence maximum shifted to the blue to a similar extent upon the addition of the saccharide inhibitors tri-(N-acetyl-D-glucosamine) and the cell-wall tetrasaccharide (GlcNAc-MurNAc)(2). The modified enzyme bound these two saccharides with nearly the same binding constants as those found for native lysozyme and for lysozyme that was reduced and reoxidized. Since the side chain of homoserine is similar in size to that of aspartic acid, it is concluded that the loss of enzymatic activity is the direct result of the chemical modification of the carboxyl side chain of aspartic acid 52, thus showing that this amino acid is essential for the catalytic action of the enzyme.
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PMID:Chemical conversion of aspartic acid 52, a catalytic residue in hen egg-white lysozyme, to homoserine. 452 56

Spherules of Coccidioides immitis strain Silveira produced in vitro were treated with chitinase and lysozyme. The walls of merthiolate-killed mature endosporulating spherules were degraded by chitinase (500 mug/ml) and by lysozyme (100 and 500 mug/ml). Thus, as was visible through the light microscope, the spherule wall was reduced in thickness from 1 to 2 mum to less than 0.5 mum. The degradation was evident also by release of N-acetylglucosamine, three times as much N-acetylglucosamine being released by chitinase in 12 h as was released by lysozyme in 3 days. However, the effect of lysozyme on living mature spherules was in marked contrast to the effect of chitinase in that treatment with lysozyme led to marked reduction in viability. Exposure to lysozyme (500 mug/ml) for 48 h permitted survival of only 0 to 0.2% of spherules. Thinning of the walls was observed only in the larger spherules (25-35 mum) treated with lysozyme. By contrast, chitinase (500 mug/ml) led to complete dissolution of the walls of living mature spherules but the viability of the liberated endospores was unaffected during contact with chitinase for 48 h. Living non-endosporulating immature spherules and free endospores were also rendered nonviable by lysozyme but not by chitinase.
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PMID:Effects of lysozyme and chitinase on the spherules of Coccidioides immitis in vitro. 476 5

Recent literature on the antibiotics enduracidin, moenomycin, prasinomycin, and 11.837 RP suggested an interaction with murein synthesis. Incubation of sensitive strains from Bacillus cereus and Staphylococcus aureus in a "wall medium" containing labeled l-alanine showed that all four antibiotics inhibited the incorporation of alanine into murein and gave rise to accumulation of radioactive uridine diphosphate-N-acetyl-muramyl (UDP-MurNAc)-pentapeptide. Peptidoglycan was synthesized when the particulate enzyme of B. stearothermophilus was incubated with the murein precursors UDP-N-acetyl-glucosamine (UDP-GlcNAc) and UDP-MurNAc-pentapeptide. The newly formed polymer was less accessible for lysozyme and more strongly bound to the acceptor than the same product from the Escherichia coli particulate enzyme. After incubation in the presence of penicillin, a greater part of the peptidoglycan was lysozyme sensitive and more loosely bound to the acceptor. The antibiotics enduracidin, moenomycin, prasinomycin, and 11.837 RP inhibited peptidoglycan synthesis by the B. stearothermophilus particulate enzyme. The rate of synthesis of GlcNAc-MurNAc(-pentapeptide)-P-P-phospholipid was independent from the addition of these antibiotics, but its utilization was strongly inhibited. With the present results, it is not possible to distinguish the mechanisms of action of enduracidin, moenomycin, prasinomycin, and 11.837 RP from the mechanisms of action of vancomycin and ristocetin.
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PMID:In vivo and in vitro action of new antibiotics interfering with the utilization of N-acetyl-glucosamine-N-acetyl-muramyl-pentapeptide. 500 Nov 98


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