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)

Main points given in the above reports can be summarized as follows. Multiple unfolded forms exist for lysozyme as well as for RNase. The existence of fast- and slow-folding forms appears to be a general phenomenon; it has been confirmed for a number of globular proteins, which contain proline residues. The major slow refolding reaction of RNase A is a sequential process via structural intermediates. A rapidly formed intermediate has also been detected on the direct UF----N refolding pathway of lysozyme. The activated state for folding of lysozyme shows a conformation similar to the native protein in terms of packing of hydrophobic groups. This suggests that, in terms of compactness, the rate-limiting step occurs at a late stage of the refolding process. A protein homologous to lysozyme, alpha-lactalbumin, shows similar kinetics although alpha-lactalbumin shows an apparent equilibrium unfolding intermediate. The location of the rate-limiting step close to the native state has also been suggested for other proteins. It still remains open whether this is a general property of protein folding reactions. As shown for the unfolding of Mb, the multi-probe kinetic measurements will be a powerful tool for investigating the mechanism of folding, in particular for characterizing structural kinetic intermediates. The dynamics of local fluctuations of a well-defined part of RNase S can be monitored by NMR measurements of NH proton exchange. An increasing number of experimental and theoretical studies are focussing on the problem of protein dynamics. Application of NMR methods to protein folding should give extensive information about the structure of intermediates, which cannot be given by other techniques.
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PMID:Experimental studies of folding kinetics and structural dynamics of small proteins. 639 21

The complete sequence of 129 amino acids has been determined for one of three closely related lysozymes c purified from cow stomach mucosa. The sequence differs from those known for 17 other lysozymes c at 39-60 positions, at one of which there has been a deletion of 1 amino acid. The glutamate replacement at position 101 and the deletion of proline at position 102 eliminate the aspartyl-prolyl bond that is present between these positions in all other mammalian lysozymes c tested. This bond appears to be the most acid-sensitive one in such lysozymes at physiological temperature. Of the 40 positions previously found to be invariant among lysozymes c, only one has undergone substitution in the cow lineage. This modest number of changes at novel positions is consistent with the inference, based on tree analysis and antigenic comparisons, that the tempo of evolutionary change in the cow lysozyme lineage has not been radically different from that in other lysozyme c lineages. The mutations responsible for the distinctive catalytic properties and stability of cow lysozyme c could be a minor fraction of the total that have been fixed in the cow lineage.
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PMID:Stomach lysozymes of ruminants. II. Amino acid sequence of cow lysozyme 2 and immunological comparisons with other lysozymes. 647 12

Analyses of whole and parotid saliva were performed in ten patients with subjective symptoms resembling galvanic pain and in their eight asymptomatic counterparts. Salivary flow rates, protein, IgA, lysozyme, sodium, potassium, chloride, calcium phosphate, copper, and magnesium contents were measured. The concentrations of protein, sodium, chloride, and phosphate in the whole saliva of the patients with symptoms were significantly higher, but concentrations of calcium, magnesium, and IgA were lower than in the asymptomatic controls. In parotid saliva, too, protein, lysozyme, and calcium concentrations were significantly altered in patients with oral symptoms. The analysis of free amino acids serine, proline, glutamic acid + glutamine, and glycine in the whole saliva did not show any significant differences between the two groups studied. The results suggest the importance of salivary contents in the development of oral soreness. Such changes in the salivary constituents could modulate the amount and character of the salivary macromolecules absorbed onto the teeth. This could lead to passivation or activation of the surfaces in metallic restorations and consequently to the onset of the intraoral electric currents.
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PMID:Salivary content of patients with subjective symptoms resembling galvanic pain. 659 63

A strong lytic activity against Micrococcus luteus was demonstrated in abomasal secretions from calf, adult cattle, goat and sheep. This bacteriolytic activity was undetectable in other secretions. Bacteriolysis was caused by a glycosidase displaying endo-N-acetylmuramoylhydrolase specificity (EC 3.2.1.17) and was further characterized in the calf. This lysozyme also displayed significant chitinase activity. Immunofluorescence microscopy confirmed the secretion of lysozyme by abomasal gastric glands exclusively. Electrofocusing revealed multiple molecular forms, the predominant one (more than 80%) being characterized by Mr approx. 15,000, pH optimum 5.0, pl 7.5 and remarkable conformational stability. The lytic activity of lysozyme was ionic strength dependent and competitive inhibition was observed with both N-acetyl glucosamine and N-acetyl-muramic acid. Amino-acid analysis demonstrated common characteristics with known lysozymes, i.e. four disulphide bridges, two proline and N-terminal lysine. Structural homology between the three ruminant lysozymes was established by immunological cross-reactivity.
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PMID:Lysozyme, an abomasal enzyme in the ruminants. 667 86

We have investigated the effect of 12 solvents and several amino acids on the fluorescence of O-(4-methylumbelliferyl)-glycosides. We showed that: i) the fluorescence quenching is not related to the dielectric constant of the solvents: the fluorescence intensity was maximal in water (d = 80) and in acetic acid (d = 6.2) and was at least ten times lower in acetone (d = 21) and in dioxane (d = 2.2); ii) the fluorescence of O-(4-methylumbelliferyl)-N-acetyl-beta-glucosaminide is not quenched in the presence of various amino acids including arginine, asparagine, aspartate, histidine, leucine, phenylalanine and proline; iii) the fluorescence of O-(4-methylumbelliferyl)-glycoside is quenched by sulfur, phenol and indole amino acids or derivatives containing sulfur, phenol or indole groups. The changes in fluorescence intensities of O-(4-methylumbelliferyl)-glycosides upon binding to concanavalin A, wheat germ agglutinin and lysozyme are discussed with regard to the amino acid content of their binding sites.
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PMID:Protein-sugar interactions: environmental effect on the fluorescence of O-(4-methylumbelliferyl)-glycosides. 668 82

The effect of four osmotic stabilizers on the radiometric detection of osmotically sensitive populations of E. coli, S. typhimurium, and E. cloacae was studied. The addition of sucrose, sorbitol, glycerol, or ethylene glycoll to BACTEC 6B blood culture medium failed to improve the sensitivity of the system and produced an inhibitory effect on the level of 14CO2 released by organisms previously exposed to lysozyme and ECTA or to penicillin followed by the lysozyme treatment. The same effect was observed both in blood free media and simulated blood cultures. The addition of proline to sucrose-containing hypertonic media had no effect on growth index readings.
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PMID:The effect of osmotic stabilizers on the radiometric detection of osmotically sensitive populations of some gram-negative bacteria. 680 67

The spore-coat fraction from Bacillus megaterium KM, when prepared by extraction of lysozyme-digested integuments with SDS (sodium dodecyl sulphate) and urea, contains three N-terminal residues and a major component of apparent mol.wt. 17500. Electron microscopy of this fraction shows it to consist of an ordered multilamellar structure similar to that which forms the coat region of intact spores. The 17500-dalton protein, which has been purified to homogeneity, has an N-terminal methionine residue, has high contents of glycine, proline, cysteine and acidic amino acids and readily polymerized even in the presence of thiol-reducing agents. It is first synthesized between late Stage IV and early Stage V, which correlates with the morphological appearance of spore coat. Before Stage VI the 17500-dalton protein is extractable from sporangia by SDS in the absence of thiol-reducing reagents. Between Stage VI and release of mature spores the protein becomes resistant to extraction by SDS unless it is supplemented by a thiol-reducing reagent. In addition to that of the spore-coat protein, the timing of synthesis of all the integument proteins was analysed by SDS/polyacrylamide-gel electrophoresis and non-equilibrium pH-gradient electrophoresis. Several integument proteins are conservatively synthesized from as early as 1h after the end of exponential growth (t1), which may reflect protein incorporation into the spore outer membrane.
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PMID:Characterization, purification and synthesis of spore-coat protein in Bacillus megaterium KM. 680 68

Bulgecins are O-sulfonated glycopeptides that are able to enhance the antibacterial activity of beta-lactam antibiotics. The 70-kDa soluble lytic transglycosylase (SLT70) from Escherichia coli forms a specific target of these compounds. Using X-ray crystallography, the three-dimensional structure of a complex of SLT70 with bulgecin A has been determined to 2.8-A resolution and refined to an R factor of 19.5%. The model contains all 618 amino acids of SLT70 and a single molecule of bound bulgecin, located in the active site of the enzyme. The glycopeptide inhibitor is bound in an extended conformation occupying sites analogous to the B, C, and D subsites of lysozyme. Upon binding of bulgecin, the three-stranded antiparallel beta-sheet in the C domain shows a pronounced shift toward the inhibitor. In subsite D, the proposed catalytic residue Glu478 forms a hydrogen bond to the hydroxymethyl oxygen of the proline part of bulgecin and interacts electrostatically with the proline NH2+ group. These interactions, in addition to the interactions observed for the 2-acetamido group of the N-acetylglucosamine residue bound in subsite C, may explain the strong inhibition of SLT70 activity by bulgecin, suggesting that bulgecin acts as an analogue of an oxocarbonium ion intermediate in the reaction catalyzed by SLT70. The structure of the SLT70--bulgecin A complex may be of assistance in the rational design of novel antibiotics.
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PMID:Structure of the 70-kDa soluble lytic transglycosylase complexed with bulgecin A. Implications for the enzymatic mechanism. 754 26

To determine the effects of different amino acids on the structure and stability of an alpha-helix in the context of a globular protein, all 19 naturally-occurring amino acids were substituted for Ser44 in phage T4 lysozyme. A more restricted set of nine replacements was also made for Val131. Ser44 and Val131 are two of a very limited number of possible sites in T4 lysozyme that are well within alpha-helices, are solvent-exposed and relatively free of interactions with neighboring residues, and are not involved in crystal contacts. High resolution structures for the majority of the mutants, some of which crystallized non-isomorphously with wild-type, were determined. With the exception of proline, the amino acid substitutions caused little if any perturbation of the alpha-helix backbone. Also the beta-branched residues Thr, Val and Ile show no indication of either side-chain or backbone distortion. Therefore, other than proline, there is no evidence that differences in helix propensities are associated with different amounts of strain introduced into the helix. For reference, and also to allow estimates of side-chain entropy, a survey was made of side-chain conformations in 100 well-refined protein structures. As noted previously all side-chains within alpha-helices strongly avoid the g- conformation (chi 1 approximately 60 degrees). This restricts the beta-branched residues Thr, Val and Ile to a single conformer (g+, chi 1 approximately -60 degrees). Asp, Asn, Met and Ser within helices also overwhelmingly prefer the g+ conformation. For Arg, Cys, Gln, Glu, Leu and Lys the t (chi 1 approximately 180 degrees) and g+ conformers are populated roughly equally. Only the aromatic residues, His, Tyr, Trp and Phe prefer the t conformation. These preferences are the same whether the side-chain is buried or solvent-exposed. In general, the side-chain conformations adopted by the residues substituted at positions 44 and 131 correspond to the most commonly observed conformation for the same amino acid in helices in known protein structures. The changes in protein stability for the replacements at site 131 in general agree well with those at site 44 (correlation r = 0.97), suggesting that these may be representative of substitutions at fully solvent-exposed sites in the middle of alpha-helices. The free energy values also agree quite well with those observed for equivalent replacements in a number of soluble alpha-helical model peptides and with data from "host-guest" studies and statistical surveys (r = 0.69 to 0.93).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Determination of alpha-helix propensity within the context of a folded protein. Sites 44 and 131 in bacteriophage T4 lysozyme. 828 84

Dilute aqueous solutions of BSA or lysozyme gave positive tests for peroxides after exposure to reactive oxygen species. The reactive species were generated by gamma-irradiation, reduction of H2O2 with Fe2+ ions or thermal decomposition of an azo compound. Peroxides were assayed by an iodometric method. Identification of the new groups as hydroperoxides was confirmed by their ability to oxidize a range of compounds and by the kinetics of their reaction with iodide. The hydroperoxide groups were bound to the proteins and their yields (G values) corresponded to 1.2 -OOH groups per 100 eV of radiation energy absorbed for BSA, and 0.8 for lysozyme. The oxygen free radicals effective in protein peroxidation were the hydroxyl and organic peroxyl, but not superoxide or its protonated form. The efficiency of BSA peroxidation initiated by the hydroxyl radicals was 40%. Protein peroxides decayed spontaneously with a half-life of about 1.5 days at 20 degrees C. Exposure of the common amino acids to hydroxyl free radicals showed that six of them (glutamate, isoleucine, leucine, lysine, proline and valine) were peroxidized with similar efficiency to the proteins, whereas the rest were inert or much less susceptible. These results suggest that some proteins may be peroxidized by a variety of agents in vivo and that their subsequent reactions with protective agents, such as ascorbate or glutathione, may decrease the antioxidant potential of cells and tissues.
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PMID:Formation of peroxides in amino acids and proteins exposed to oxygen free radicals. 843 71


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