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)

Cell-free hemolymph from silkworm (Bombyx mori) larvae can kill Escherichia coli B/SM. The bactericidal principle can be resolved into at least two factors. One is a lysozyme-like enzyme that can be absorbed on crab shell chitin and on bentonite, and the other (cofactor) is an anionic factor that is of low molecular weight, can pass through the chitin column and a carboxymethyl-cellulose column, and can be eluted from a diethylaminoethyl-cellulose column at mu = 0.15 and pH 7.5. Egg-white lysozyme cannot replace the silkworm lysozyme-like enzyme for restoring the bactericidal activity when it is mixed with the cofactor, although it can enhance the bactericidal activity of the mixture of silkworm enzyme and cofactor. Mg2+ and Ca2+ can inhibit the bactericidal activity.
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PMID:Bactericidal activity of the normal, cell-free hemolymph of silkworms (Bombyx mori). 32 74

The properties of a smooth phage resistant variant of Brucella abortus were studied in an attempt to determine the mechanism of phage resistance. This strain was fully capable of adsorbing phage but penetration, and hence replication, did not occur. No evidence of lysogeny or a phage carrier state could be obtained and gross chemical differences between the resistant strain and its phage susceptible parent were not detected. The phage resistant variant showed increased resistance to lysis from without, either by phage or by lysozyme, in the presence of chelating agents. It was concluded that resistance was the result of a modification in cell wall structure conferring resistance to lysozyme-like enzymes, thus preventing penetration of phage.
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PMID:Studies on a smooth phage resistant variant of Brucella abortus II. Mechanism of phage resistance. 81 43

Observations of the authors of the present work permit to put forward the following suppositions on the biological significance of the lysozyme sign included into the number of sign-of the staphylococcus pathogenicity: 1) the action of the lysozyme-like enzyme (LLE) as a facs for increasing the permeability of the cell wall and thus promoting the exit of the "pathogenicity enzymes"; 2) its participation in the growth and division of staphylococci, pointing to the differences in the rate of the growth of the cultures forming and nonforming the LLE; 3) participation of the LLE in the microbial antagonism processes--crude LLE (in the form of lipoproteid complex) stipulated the antimicrobial effect against a number of nonpathogenic microbes. None of these hypotheses can be accepted without further investigations, particularly with the purified enzyme.
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PMID:[Role of the lysozyme-like enzyme of staphylococci in their pathogenicity]. 102 42

On the basis of studying 855 strains of various staphylococci it was shown that production of a lysozyme-like enzyme (LLE) failed to serve as a characteristic sign for all the representatives of Staphylococcus genus. It was mostly observed in S. aureus (in 85% of the strains). In nonpathogenic strains of S. epidermidis LLE could not be revealed either by the dish or by affine chromatography on chitin; among S. epidermidis, isolated from the patients there were cultures which did or did not form the LLE. Cultures occupying an intermediate position (coagulase-negative or mannite-negative) formed the LLE in 66.9% of cases. It was shown that the virulence and the general biological activity of the lysozyme-positive intermediate strains were higher than in the lysozyme-negative ones.
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PMID:[Production of a lysozyme-like enzyme by various representatives of the genus Staphylococcus]. 112 15

Site-directed mutagenesis experiments designed to identify the active site of Bacillus licheniformis endo-beta-1,3-1,4-D-glucan 4-glucanohydrolase (beta-glucanase) have been performed. Putative catalytic residues were chosen on the basis of sequence similarity analysis to viral and eukaryotic lysozymes. Four mutant enzymes were expressed and purified from recombinant E. coli and their kinetics analysed with barley beta-glucan. Replacement of Glu134 by Gln produced a mutant (E134Q) that retains less than 0.3% of the wild-type activity. The other mutants, D133N, E160Q and D179N, are active but show different kinetic parameters relative to wild-type indicative of their participation in substrate binding and transition-state complex stabilization. Glu134 is essential for activity; it is comprised in a region of high sequence similarity to the active site of T4 lysozyme and matches the position of the general acid catalyst. These results strongly support a lysozyme-like mechanism for this family of Bacillus beta-glucan hydrolases with Glu134 being the essential acid catalyst.
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PMID:Essential catalytic role of Glu134 in endo-beta-1,3-1,4-D-glucan 4-glucanohydrolase from B. licheniformis as determined by site-directed mutagenesis. 135 72

The level of the antilysozyme activity of S. flexneri in ensuring the high level of their phage resistance has been studied. The realization of the phage protective effect of antilysozyme activity has been noted to occur due to disturbances in the lysis of infected bacteria by phage-synthetized lysozyme-like enzyme. The direct relationship between the level of the lysozyme production of bacteriophages and their capacity for overcoming the antilysozyme protection of the host bacterium has been shown.
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PMID:[The role of the antilysozyme activity of Shigella flexneri as a factor controlling the degree of its resistance to the lytic action of bacteriophages]. 269 89

Larvae of the cabbage white butterfly, Pieris brassicae, were reared on a semisynthetic diet with or without 20 ppm of the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and using three assays the sera were subsequently tested for natural antibacterial activity against Bacillus cereus, Escherichia coli K12, and Micrococcus luteus. These assays showed that exposure of larvae to 2,4,5-T lowered the antibacterial activity of the serum against E. coli and M. luteus compared with control animals. Spectrophotometric tests for the presence of a lysozyme-like principle in the serum also revealed similar trends with a significant loss of enzyme activity in 2,4,5-T-treated insects. Overall total serum protein levels of control and 2,4,5-T-treated insects were similar, suggesting a specific effect of the herbicide on certain serum components such as lysozyme. The possible mode of action of the herbicide on production of antibacterial factors is discussed.
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PMID:Effect of exposure of Pieris brassicae larvae to 2,4,5-trichlorophenoxyacetic acid on the natural antibacterial activity of serum. 273 19

Class II chitinases (EC 3.2.1.14) are plant defense proteins. They hydrolyze chitin, an insoluble beta-1,4-linked polymer of N-acetylglucosamine (NAG), which is a major cell-wall component of many fungal hyphae. We previously reported the three-dimensional structure of the 26 kDa class II endochitinase from barley seeds at 2.8 A resolution, determined using multiple isomorphous replacement (MIR) methods. Here, we report the crystallographic refinement of this chitinase structure against data to 1.8 A resolution using rounds of hand rebuilding coupled with molecular dynamics (X-PLOR). The final model has an R-value of 18.1% for the 5.0 to 1.8 A data shell and 19.8% for the 10.0 to 1.8 A shell, and root-mean-square deviations from standard bond lengths and angles of 0.017 A and 2.88 degrees, respectively. The 243 residue molecule has one beta-sheet, ten alpha-helices and three disulfide bonds; 129 water molecules are included in the final model. We show structural comparisons confirming that chitinase secondary structure resembles lysozyme at the active site region. Based on substrate binding to lysozyme, we have built a hypothetical model for the binding of a hexasaccharide into the pronounced active site cleft of chitinase. This provides the first view of likely substrate interactions from this family of enzymes; the model is consistent with a lysozyme-like mechanism of action in which Glu67 acts as proton donor and Glu89 is likely to stabilize the transition state oxycarbonium ion. These binding site residues, and many hydrophobic residues are conserved in a range of plant chitinases. This endochitinase structure will serve as a model for other plant chitinases, and that catalytic models based on this structure will be applicable to the entire enzyme family.
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PMID:The refined crystal structure of an endochitinase from Hordeum vulgare L. seeds at 1.8 A resolution. 773 49

The integrity of the bacterial cell wall depends on the balanced action of several peptidoglycan (murein) synthesizing and degrading enzymes. Penicillin inhibits the enzymes responsible for peptide crosslinks in the peptidoglycan polymer. Enzymes that act solely on the glycosidic bonds are insensitive to this antibiotic, thus offering a target for the design of antibiotics distinct from the beta-lactams. Here we report the X-ray structure of the periplasmic soluble lytic transglycosylase (SLT; M(r) 70,000) from Escherichia coli. This unique bacterial exomuramidase cleaves the beta-1,4-glycosidic bonds of peptidoglycan to produce small 1,6-anhydromuropeptides. The structure of SLT reveals a 'superhelical' ring of alpha-helices with a separate domain on top which resembles the fold of lysozyme. Site-directed mutagenesis and a crystallographic inhibitor-binding study confirmed that the lysozyme-like domain contains the active site of SLT.
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PMID:Doughnut-shaped structure of a bacterial muramidase revealed by X-ray crystallography. 810 71

The principal role of lysozyme is to prevent bacterial invasion at body surfaces. We are interested in how lysozyme is regulated at the surface of the respiratory tract, where the serous gland cell is regarded as the primary cellular source of this enzyme. Since the cow genome contains at least 10 lysozyme-like genes, our objective was to determine which of them are expressed in the cow tracheal gland serous cell. By screening tracheal cDNA libraries with a probe constructed from the cDNA encoding stomach lysozyme 2, we obtained 3 lysozyme cDNAs: 5a (1023 base pairs (bp)), 7a (1060 bp), and 14d (1249 bp). cDNA 7a corresponds to a previously reported gene (showing sequence identity to the stomach 2 lysozyme gene), whereas cDNAs 5a and 14d correspond to lysozyme genes not previously reported. Northern blot analysis of cow tracheal RNA showed lysozyme mRNAs of three distinct lengths. Based on hybridization with probes specific for each cDNA, we determined that the longest transcript corresponded to cDNA 5a, the shortest to 7a, and the intermediate-length transcript to 14d. Cultured cow tracheal gland serous cell RNA, reverse transcribed and amplified by the polymerase chain reaction with primers common to all three cDNAs, yielded a product that hybridized to oligonucleotide probes specific for all three cDNAs but most strongly to that for 5a. These results indicate that multiple lysozyme mRNAs are expressed in the cow trachea and that the lysozyme encoded by cDNA 5a is the major form expressed in the tracheal gland serous cell. This serous cell lysozyme is predicted to differ importantly in structure from both 7a and 14d lysozymes, with an arginine:lysine ratio almost 10-fold higher. The sequence differences may underlie functional differences, including variable resistance to proteolysis and variable affinity for large polyanions (e.g. mucins) found in the respiratory tract lumen.
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PMID:Multiple cDNA sequences of bovine tracheal lysozyme. 826 86


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