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)

Chitin dissolved in N,N-dimethylacetamide, N-methyl-2-pyrrolidone and their mixed solvents in the presence of 5% LiCl was treated with acetic anhydride-pyridine, and the mixture solution was heated at 100 degrees C for 6 h to give a partially O-acetylated chitin gel. Chitin dissolved in these solvents in the presence of 5% LiCl was mixed with pyridine, and the mixture solution was heated at 60 degrees C for 5 h to give a chitin gel. Both the gels were rigid and transparent, and their properties and the rate of the hydrolysis of the chitin xerogel by hen-egg white lysozyme were essentially similar to those of N-acetylchitosan gel prepared by chemical N-acetylation of chitosan.
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PMID:Chitin gels. 256 47

Cisplatin (CDDP) containing albumin microspheres and microcapsules incorporating biodegradable macromolecules, chitin and chitosan, were prepared, and their CDDP content and releasing ability and susceptibility to various enzymes were examined. Chitin was incorporated during preparation of the microspheres, while chitosan was used to treat preformed microspheres. CDDP content was remarkably increased by chitin; when chitin was incorporated at a concentration of 1.5%, the CDDP content of the microspheres was found to be 16.2% (1.8 times that with no addition of chitin). CDDP release was suppressed by chitin and chitosan. The 50% CDDP release time was about 1.5 h when no chitin was added, but about 16 h was required when chitin was incorporated into the microspheres at a concentration of 1.5%. Chitin and chitosan suppressed the decomposition by protease. The microspheres treated with 70% deacetylated chitosan showed the greatest susceptibility to lysozyme. In conclusion, CDDP release can be controlled by the use of chitin or chitosan, and the microspheres should show no immunogenicity in vivo because of their susceptibility to lysozyme.
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PMID:Preparation and release characteristics of cisplatin albumin microspheres containing chitin and treated with chitosan. 263 57

Pathogenic mechanisms in infectious diseases often involve specific receptor-ligand interactions of cells and soluble molecules. To further elucidate structure-function relations for shigella toxin receptors, we studied binding of purified 125I-labeled toxin and biologic response under various conditions in an experimental model using HeLa cells. Response to toxin was reversibly inhibited by treatment of cells with trypsin or tunicamycin, an inhibitor of glycoprotein synthesis that also significantly inhibited toxin binding, a result indicating that the receptor is an N-linked glycoprotein. Removal of terminal beta-linked galactose from the HeLa cell surface with beta-galactosidase increased toxin binding and activity, and it also potentiated the effects of lysozyme and wheat-germ agglutinin, which recognize oligomeric beta 1----4-linked N-acetyl-D-glucosamine and inhibit toxin activity as well. Incubation of cells with beta-N-acetylglucosaminidase, which cleaves terminal beta-linked N-acetyl-D-glucosamine, inhibited toxin activity. Effects of beta-galactosidase were reversed by readdition of galactose to cell-surface oligosaccharide acceptors. The data demonstrate that alterations of a single sugar on cell-surface glycoproteins may have a dramatic effect on receptor activity and indicate that shigella toxin is a sugar-binding protein with specificity for beta 1----4-linked N-acetyl-D-glucosamine.
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PMID:Pathogenesis of shigella diarrhea: evidence for an N-linked glycoprotein shigella toxin receptor and receptor modulation by beta-galactosidase. 300 5

A method to determine intrinsic binding constants of lysozyme with substrate analogues such as N-acetyl-D-glucosamine dimer and trimer is proposed. The method is based on the competitive interaction of an anionic azo dye with substrate analogues for lysozyme. There are two binding sites for substrate analogues and dyes, respectively, on lysozyme. One binding mode of the substrate analogues to subsites D-F on lysozyme was non-competitive, and another binding mode to subsites A-C was competitive with the dye. From the binding constants obtained it is suggested that the binding of the substrate analogues to subsite D on lysozyme is weaker than the binding to the other subsites.
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PMID:Determination of binding constants for N-acetyl-D-glucosamine oligomers with lysozyme. 343 26

In the cross-linking reaction of lysozyme between Leu129 (alpha-COO-) and Lys13 (epsilon-NH3+) using imidazole and 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC), a side reaction of the peptide bond inversion from alpha to beta between Asp101 and Gly102 was greatly reduced by addition of beta-(1,4)-linked trimer of N-acetyl-D-glucosamine [(NAG)3]. When methylamine or 2-hydroxyethylamine was further added, the extent of the cross-link formation was decreased and the derivative where the alpha-carboxyl group of Leu129 was modified with the amine was newly obtained. On the other hand, when ammonia was added, the beta-carboxyl group of Asp119 instead of the alpha-carboxyl group was mainly amidated. From these results, the presence of a salt bridge between Asp119 and Arg125 besides that between Lys13 and Leu129, is proposed. Enzymatic activities of the derivatives prepared here indicated that the modification of the alpha-carboxyl group reduced the activity to approximately 90% of that of native lysozyme. Des-Leu129 lysozyme, which lacks Leu129, also showed approximately 90% of the activity of native lysozyme. Therefore, the salt bridge between Lys13 and Leu129 may play some role in maintaining the active conformation of lysozyme.
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PMID:Highly controlled carbodiimide reaction for the modification of lysozyme. Modification of Leu129 or Asp119. 350 4

A mechanism for the selective modification of Asp-101 in hen egg-white lysozyme with an amine nucleophile catalyzed by 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC) was investigated using ethanolamine as a nucleophile at pH 5.0 and room temperature. In the presence of N-acetyl-D-glucosamine (NAG) and its oligomers [(NAG)n, n = 2 and 3] under the conditions with which about 90% of lysozyme was calculated to form complexes, the formation of Asp-101 modified lysozyme decreased markedly but to different degrees, that is (NAG)3 was the most and NAG the least effective. When the lysozyme derivative, in which Trp-62 in the active site cleft was oxidized to oxindolealanine (Ox-62 lysozyme), was used in place of native lysozyme, the formation of Asp-101 modified derivative decreased to about half, which was similar to the decrease in the presence of (NAG)2. In the presence of 0.5 M NaCl, on the other hand, the formation of Asp-101 modified lysozyme was considerably enhanced. From these observations, it is concluded that EDC binds to the active site cleft of lysozyme to specifically activate Asp-101. The affinity of EDC to the active site of lysozyme is partly due to the hydrophobic interaction of EDC with the Trp-62 residue at sub-site B of lysozyme. EDC is an activating reagent for carboxyl groups unlike most active site-directed reagents which produce final products directly. Therefore, the active site-directed nature of EDC was very useful because it made it possible to selectively introduce various amines as needed at a particular carboxyl group of lysozyme.
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PMID:Specific carbodiimide-binding mechanism for the selective modification of the aspartic acid-101 residue of lysozyme in the carbodiimide-amine reaction. 371 Oct 72

Dinitrophenylation of hen egg white lysozyme with 2,4-dinitrofluorobenzene (DNFB) was carried out at pH 7-11 and room temperature in order to examine whether dinitrophenylation could be applied to determine the environments of individual amino groups in lysozyme or not. Lightly dinitrophenylated lysozyme was reduced, S-carboxymethylated and then subjected to reversed-phase high-performance liquid chromatography (RP-HPLC). All tryptic peptides, which contained dinitrophenylated amino groups (one alpha-amino group, Lys 1(alpha), and six epsilon-amino groups, Lys 1(epsilon), Lys 13, Lys 33, Lys 96, Lys 97, and Lys 116), could be separated and monitored by absorbance measurement at 360 nm on RP-HPLC. The relative reactivities of individual amino groups, determined from the relative peak areas of dinitrophenylated tryptic peptides at 360 nm, were found to be sensitive to the reaction pH and to the presence of the trimer of N-acetyl-D-glucosamine or NaCl. It was concluded that dinitrophenylation of a protein with DNFB followed by peptide analysis by RP-HPLC with detection at 360 nm is a good method for probing the environments of individual amino groups in the protein.
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PMID:Dinitrophenylation as a probe for the determination of environments of amino groups in protein. Reactivities of individual amino groups in lysozyme. 375 34

In a two-step process, esterification and ammonolysis, Glu-35 and Asp-52 in lysozyme were amidated to glutamine and asparagine residues. Since the side chains of glutamine and asparagine are almost equal in size to those of glutamic acid and aspartic acid, these conversions would provide appropriate derivatives to elucidate the catalytic participations of these residues. The enzymatic activities of the resulting [Gln35]lysozyme and [Asn52]lysozyme were found to be less than 4% of that of native lysozyme in a pH range of 3.4-8.0. As these derivatives were inactive, we could determine the dissociation constants (Ks values) for the binding of beta-1,4-linked n-mer, a hexasaccharide of N-acetyl-D-glucosamine, to [Gln35]lysozyme and [Asn52] lysozyme. The values of Ks at pH 5.5 and 40 degrees C were 1.6 X 10(-5) M for [Gln35]lysozyme and 2.7 X 10(-5) M for [Asn52]lysozyme. These values are similar to that for native lysozyme. The results are direct proof for the involvements of Glu35 and Asp52 in the catalytic action of lysozyme. A method for ammonolysis of ester groups in proteins in liquid ammonia is described and will be useful for amidation of carboxyl groups of proteins.
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PMID:Chemical mutations of the catalytic carboxyl groups in lysozyme to the corresponding amides. 375 81

The ability of lysozyme to aggregate and lyse the gram-negative capnophilic periodontal microorganism Capnocytophaga gingivalis 2010 was monitored optically at 540 nm. Both hen egg white and chromatographically purified human lysozymes had significant but similar aggregation potentials for both logarithmic- and stationary-phase bacteria. In general, an increase in enzyme concentration resulted in a graded increase in both the initial and maximum changes in turbidity which occurred during the reaction period. The greatest change in turbidity occurred within the initial minutes of interaction of lysozyme and the cells, and the extent of aggregation paralleled a rapid depletion of lysozyme by the suspensions during the first minute of its incubation with the bacteria. Interestingly, the muramidase inhibitors N-acetyl-D-glucosamine and histamine did not block aggregation, whereas maleylation of lysozyme completely inhibited its aggregating ability. Demaleylation, however, restored aggregation activity comparable to the native enzyme, indicating that maleylated lysozyme retained its integrity and that aggregation was primarily dependent on charge. The addition of up to physiological concentrations of NaHCO3 and NaCl to cell aggregates resulted in varying degrees of deaggregation and lysis. Surprisingly, ultrastructural analysis of lysozyme-treated cells revealed morphological changes with or without the addition of salt. Damage appeared to occur at the blunted polar end of the cells where there was a large spherical outpouching bordered by a damaged cell envelope. Damaged cells uniformly contained dense granular cytoplasmic debris. In effect, the cationic enzyme lysed C. gingivalis 2010, which was not apparent in the spectrophotometric assay. The paradoxical finding that during bacterial aggregation there was lysis may be of significance to the further elucidation of lysozyme's antibacterial role in the gingival sulcus.
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PMID:Lysozyme-mediated aggregation and lysis of the periodontal microorganism Capnocytophaga gingivalis 2010. 396 24

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


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