Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carbon-13 NMR spectroscopy has been used to further document the interaction, at low and high temperatures, of N-acetylglucosamine and its short polymers with hen egg-white lysozyme. The results have been compared with the corresponding X-ray crystallographic data. Two domains, the active site and the hydrophobic box, have been found by NMR to undergo conformational rearrangement while X-ray crystallography only detected changes located in the active site. The extent of the modifications induced by inhibitor binding was proportional to the inhibitor size. The two techniques concurred to show that even in the presence of monosaccharide (N-acetylglucosamine), more than one subsite of the enzyme was occupied at high temperature, the binding at the C-site being the best defined. The thermal transition of lysozyme still occurred in solution when inhibitors were bound. However, in the solid state, crystallographic data showed that the transition was hindered.
 ...
PMID:Effect of inhibitors on conformational changes in hen lysozyme around thermal transition point in solution and solid state. 216 67

Using a technique based on specific enzyme sorption by chitin (beta-1-4-N-acetylglucosamine), lysozyme with a molecular mass of 15,000 has been isolated from homogenates of the Ix. persulcatus ticks. Micrococci and staphylococci proved to be most sensitive to lysozyme from the Ix. persulcatus ticks, while E. coli and Salmonella were less sensitive. The minimum inhibitory concentration of lysozyme from Ix. persulcatus was 2-4 times lower than that of egg lysozyme. Lysozyme from the Ix. persulcatus ticks is resistant to heating in acid medium and loses some of its activity in alkaline medium. The loss of the activity in the both media is somewhat lower than that of egg lysozyme in analogous conditions.
 ...
PMID:[The lysozyme of Ixodes persulcatus ticks]. 221 66

The length distribution of the glycan strands in the murein (peptidoglycan) sacculus of Escherichia coli has been analyzed after solubilization of the murein by complete digestion with human serum amidase. The glycan strands released were separated according to length by reversed-phase HPLC on wide-pore Nucleosil 300 C18 material at 50 degrees C, employing a convex gradient from 5 to 11% acetonitrile. The length of the fractionated glycan strands, which carry a nonreducing 1,6-anhydromuramic acid as a natural end group, was calculated from the ratio of total to nonreducing terminal muramic acid residues. This was possible after complete hydrolysis of the isolated glycan strands by muramidase followed by separation of the released nonreducing and reducing di- and tetrasaccharides by reversed-phase HPLC on Hypersil C18. The method established allows the separation of the glycan strands of murein, a poly-GlcNAc(beta 1-4)MurNAc-polysaccharide, up to a degree of polymerization of approximately 60. The predominant lengths of the glycan strands were 5 to 10 GlcNAc(beta 1-4)MurNAc disaccharide units.
 ...
PMID:Isolation and separation of the glycan strands from murein of Escherichia coli by reversed-phase high-performance liquid chromatography. 228 38

Teichuronic acid-peptidoglycan complex isolated from Micrococcus luteus cells by lysozyme digestion in osmotically stabilized medium was treated with mild acid to cleave the linkage joining teichuronic acid to peptidoglycan. This labile linkage was shown to be the phosphodiester which joins N-acetylglucosamine, the residue located at the reducing end of the teichuronic acid, through its anomeric hydroxyl group to a 6-phosphomuramic acid, a residue of the glycan strand of peptidoglycan. 31P nuclear magnetic resonance spectroscopy of the lysozyme digest of cell walls demonstrated the presence of a phosphodiester which was converted to a phosphomonoester by the conditions which released teichuronic acid from cell walls. Reduction of acid-liberated reducing end groups by NaB3H4 followed by complete acid hydrolysis yielded [3H] glucosaminitol from the true reducing end residue of teichuronic acid and [3H]glucitol from the sites of fragmentation of teichuronic acid. The amount of N-acetylglucosamine detected was approximately stoichiometric with the amount of phosphate in the complex. Partial fragmentation of teichuronic acid provides an explanation of the previous erroneous identification of the reducing end residue.
 ...
PMID:Teichuronic acid reducing terminal N-acetylglucosamine residue linked by phosphodiester to peptidoglycan of Micrococcus luteus. 233 1

Arginine 115 in the subsite F of human lysozyme (peptidoglycan N-acetylmuramoylhydrolase, EC 3.2.1.17) was replaced with lysine, histidine, glutamine or glutamine acid by site-directed mutagenesis. The conversions which conserve positive charge, Arg115 to Lys or His (at acidic pH), have little affected on either the kinetic parameters for Micrococcus lysodeikticus cells or the activity against glycol chitin, nor on the cleavage patterns of hexa(N-acetylglucosamine) [(GlcNAc)6] and penta(N-acetylglucosamine) [(GlcNAc)5]. On the other hand, the conversions which cause loss of the positive charge, Arg115 to His (neutral and alkaline pH), Gln or Glu, not only reduced the activity against glycol chitin but also changed the cleavage patterns for (GlcNAc)6 and (GlcNAc)5. These results suggest that Arg115 is structurally required not for the specific hydrogen bonding interaction with a sugar residue but for the positively charged character in the construction of subsite F in human lysozyme.
 ...
PMID:A structural requirement in the subsite F of lysozyme. The role of arginine 115 in human lysozyme revealed by site-directed mutagenesis. 249 74

An endochitinase from centrifuged autolyzed cultures of Aspergillus nidulans has been purified 100 times. The enzyme has Mw 27,000, pI of 4.8 units, pH optimum around 5 pH units. It is unstable at temperature greater than 70 degrees C and does not have a cation requirement. It is inhibited by Hg2+, Cu2+, Ca2+ and Ag+ and it does not have muramidase activity. The enzyme depolymerizes chitin rapidly with production of high molecular weight polysaccharides, and then slowly degrades these with production of N,N'-diacetylchitobiose. The enzyme hydrolyzes N,N',N''-triacetylchitotriose with production of N,N'-diacetylchitobiose and N-acetylglucosamine and this hydrolysis is inhibited by other chitin oligomers and N-acetylglucosamine. This enzyme hydrolyzes in the same way the chitin obtained from the cell wall of Aspergillus nidulans.
 ...
PMID:Endochitinase from Aspergillus nidulans implicated in the autolysis of its cell wall. 267 5

Bordetella pertussis Tohama phases I and III were grown to the late-exponential phase in liquid medium containing [3H]diaminopimelic acid and treated by a hot (96 degrees C) sodium dodecyl sulfate extraction procedure. Washed sodium dodecyl sulfate-insoluble residue from phases I and III consisted of complexes containing protein (ca. 40%) and peptidoglycan (60%). Subsequent treatment with proteinase K yielded purified peptidoglycan which contained N-acetylglucosamine, N-acetylmuramic acid, alanine, glutamic acid, and diaminopimelic acid in molar ratios of 1:1:2:1:1 and less than 2% protein. Radiochemical analyses indicated that 3H added in diaminopimelic acid was present in peptidoglycan-protein complexes and purified peptidoglycan as diaminopimelic acid exclusively and that pertussis peptidoglycan was not O acetylated, consistent with it being degraded completely by hen egg white lysozyme. Muramidase-derived disaccharide peptide monomers and peptide-cross-linked dimers and higher oligomers were isolated by molecular-sieve chromatography; from the distribution of these peptidoglycan fragments, the extent of peptide cross-linking of both phase I and III peptidoglycan was calculated to be ca. 48%. Unambiguous determination of the structure of muramidase-derived peptidoglycan fragments by fast atom bombardment-mass spectrometry and tandem mass spectrometry indicated that the pertussis peptidoglycan monomer fraction was surprisingly homogeneous, consisting of greater than 95% N-acetylglucosaminyl-N-acetylmuramyl-alanyl-glutamyl-diaminopimelyl++ +-alanine.
 ...
PMID:Structure of Bordetella pertussis peptidoglycan. 288 47

p-Nitrophenyl beta-glycosides of N-acetylchitooligosaccharides (PNP-(GlcNAc)n n = 3-5) were examined as substrates for lysozyme [EC 3.2.1.17]. The enzyme released predominantly p-nitrophenyl N-acetyl-beta-D-glucosaminide (PNP-GlcNAc) from each substrate. Furthermore, the initial rate of PNP-GlcNAc formation in lysozyme-catalyzed hydrolysis of p-nitrophenyl penta-N-acetyl-beta-chitopentaoside (PNP-(GlcNAc)5) was about 350 and 25 times faster than those of p-nitrophenyl tri-N-acetyl-beta-chitotrioside (PNP-(GlcNAc)3) and p-nitrophenyl tetra-N-acetyl-beta-chitotetraoside (PNP-(GlcNAc)4), respectively. From these results, a new colorimetric assay method of lysozyme using PNP-(GlcNAc)5 as a substrate was developed on the basis of the determination of p-nitrophenol liberated from the substrate by lysozyme through a coupled reaction involving beta-N-acetylhexosaminidase (NAHase). The assay system gave a linear dose-response curve in the range of 2-120 micrograms of lysozyme in a 15-60 min incubation. The present assay was not significantly influenced by the ionic strength of the medium and was reproducible. This method using PNP-(GlcNAc)5 as a substrate was shown to be useful for lysozyme assay.
 ...
PMID:p-nitrophenyl penta-N-acetyl-beta-chitopentaoside as a novel synthetic substrate for the colorimetric assay of lysozyme. 297 99

The adherence of Streptococcus faecium 9790 to hydroxyapatite (HA) coated with whole saliva supernatant proteins (S-HA) or parotid fluid proteins was studied. The organism was labeled with [3H]thymidine, and adherence was estimated as the radioactivity remaining associated with the variously coated HA preparations after incubation and removal of unbound microbes by washing the adherence substratum. Adherence was time dependent and saturable, characteristics typical of oral streptococci in this in vitro adherence model system. However, adherence to S-HA, but not bare HA, was decreased 20-fold at 4 degrees C compared with room temperature. Furthermore, adherence at 4 degrees C to S-HA was decreased 20-fold relative to bare HA at 4 degrees C. Adherence to HA coated with parotid fluid proteins also was reduced at 4 degrees C. The magnitude of the temperature dependence and the inhibitory effect at 4 degrees C of whole saliva or parotid fluid pellicles on HA was unexpected. Of several sugars and amino sugars tested, the chitin saccharides, chitotriose, chitobiose, and N-acetylglucosamine caused greater than 90% inhibition of adherence to S-HA. These same saccharides were previously shown to inhibit lysozyme, polylysine, or autolytic lysis of the organism (N. J. Laible and G. R. Germaine, Infect. Immun. 48:720-728, 1985). Examination of unbound and adherent microbes revealed that lysis of the organism occurred during the adherence assays. A strong association (r = 0.83) between the extent of lysis and the extent of adherence was found under a variety of conditions. Depletion of lysozyme from saliva specimens used to coat HA resulted in a greater than 90% decrease in both cell lysis and adherence. Lysis of the microbe appeared dependent upon the presence of the saliva pellicle (coating) on HA, since solutions containing proteins desorbed from HA during mock-adherence incubations possessed lytic activity that was 2- to 10-fold too low to account for the extents of lysis observed with greater than or equal to 10(8) input cells. These results demonstrate the potential antibacterial activity of acquired salivary pellicle on enamel in vivo and the likely role of lysozyme in this activity. The data also serve to caution that this widely used in vitro adherence model will not distinguish whole-cell adherence from the adsorption of radiolabeled DNA released from lysing cells. Several additional controls are suggested that will indicate whether test microbes remain intact or lyse during adherence trials.
 ...
PMID:Potential role of lysozyme in bactericidal activity of in vitro-acquired salivary pellicle against Streptococcus faecium 9790. 302 39

Migrating embryonic cells have high levels of cell surface galactosyltransferase (GalTase) activity. It has been proposed that GalTase participates during migration by recognizing and binding to terminal N-acetylglucosamine (GlcNAc) residues on glycoconjugates within the extracellular matrix (Shur, B. D., 1982, Dev. Biol. 91:149-162). We tested this hypothesis using migrating neural crest cells as an in vitro model system. Cell surface GalTase activity was perturbed using three independent sets of reagents, and the effects on cell migration were analyzed by time-lapse microphotography. The GalTase modifier protein, alpha-lactalbumin (alpha-LA), was used to inhibit surface GalTase binding to terminal GlcNAc residues in the underlying substrate. alpha-LA inhibited neural crest cell migration on basal lamina-like matrices in a dose-dependent manner, while under identical conditions, alpha-LA had no effect on cell migration on fibronectin. Control proteins, such as lysozyme (structurally homologous to alpha-LA) and bovine serum albumin, did not effect migration on either matrix. Second, the addition of competitive GalTase substrates significantly inhibited neural crest cell migration on basal lamina-like matrices, but as above, had no effect on migration on fibronectin. Comparable concentrations of inappropriate sugars also had no effect on cell migration. Third, addition of the GalTase catalytic substrate, UDPgalactose, produced a dose-dependent increase in the rate of cell migration. Under identical conditions, the inappropriate sugar nucleotide, UDPglucose, had no effect. Quantitative enzyme assays confirmed the presence of GalTase substrates in basal lamina matrices, their absence in fibronectin matrices, and the ability of alpha-LA to inhibit GalTase activity towards basal lamina substrates. Laminin was found to be a principle GalTase substrate in the basal lamina, and when tested in vitro, alpha-LA inhibited cell migration on laminin. Together, these experiments show that neural crest cells have at least two distinct mechanisms for interacting with the substrate during migration, one that is fibronectin-dependent and one that uses GalTase recognition of basal lamina glycoconjugates.
 ...
PMID:Evidence for a novel enzymatic mechanism of neural crest cell migration on extracellular glycoconjugate matrices. 308 Apr 36


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>