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)

The environments of the binding subsites in Asp 101-modified lysozyme, in which glucosamine or ethanolamine is covalently bound to the carboxyl group of Asp 101, were investigated by chemical modification and nuclear magnetic resonance spectroscopy. Trp 62 in each of the native and the modified lysozymes was nitrophenylsulfenylated. The yield of the nitrophenylsulfenylated derivative from the lysozyme modified with glucosamine at Asp 101 (GlcN-lysozyme) was considerably lower than those from native lysozyme and from the lysozyme modified with ethanolamine at Asp 101 (EtN-lysozyme). These results suggest that Trp 62 in GlcN-lysozyme is less susceptible to nitrophenylsulfenylation. Kinetic analyses of the [Trp 62 and Asp 101]-doubly modified lysozymes indicated that the nitrophenylsulfenylation of Trp 62 in the native lysozyme, EtN-lysozyme, or GlcN-lysozyme decreased the sugar residue affinity at subsite C while increasing the binding free energy change by 2.7 kcal/mol, 1.5 kcal/mol, or 0.1 kcal/mol, respectively. Although the profile of tryptophan indole NH resonances in the 1H-NMR spectrum for EtN-lysozyme was not different from that for the native lysozyme, the indole NH resonance of Trp 62 in GlcN-lysozyme was apparently perturbed in comparison with that of native lysozyme. These results suggest that the environment of subsite C in GlcN-lysozyme is considerably different from those in native lysozyme and EtN-lysozyme. The glucosamine residue attached to Asp 101 may contact the sugar residue binding site of the lysozyme, affecting the environment of subsite C.
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PMID:State of binding subsites in Asp 101-modified lysozymes. 234 78

Reaction of beta-oligoglycosylamines obtained from carbohydrate chains of N-glycoproteins (ovalbumin, ovomucoid, riboflavin-binding glycoprotein from hen egg white, and asialofetuin) with bovine serum albumin, lysozyme, and poly(L-Asp) in presence of water-soluble carbodiimide gave rise to a series of glycoconjugates, modelling natural N-glycoproteins. Carbohydrate-peptide bond was shown to be of N-glycosylamide type with participation of Asp and Glu residues. The method allows one to obtain synthetic N-glycoproteins from oligomannoside, complex and hybrid oligosaccharide chains, and may find application both in biochemistry and biotechnology for improvement of physico-chemical properties of unglycosylated proteins.
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PMID:[Synthesis of N-glycoproteins with a native type of carbohydrate-peptide bond]. 234 12

The roles of the catalytic active-site residues aspartic acid-52 and glutamic acid-35 of chicken lysozyme (EC 3.2.1.17) have been investigated by separate in vitro mutagenesis of each residue to its corresponding amide (denoted as D52N and E35Q, respectively). The mutant enzyme D52N exhibits approximately 5% of the wild-type lytic activity against Micrococcus luteus cell walls, while there is no measurable activity associated with E35Q (0.1% +/- 0.1%). The measured dissociation constants for the chitotriose-enzyme complexes were 4.1 microM (D52N) and 13.4 microM (E35Q) vs. 8.6 microM for wild type, indicating that the alterations in catalytic properties may be due in part to binding effects as well as to direct catalytic participation of these residues. The mutant lysozymes have been expressed in and secreted from yeast and obtained at a level of approximately 5 mg per liter of culture by high-salt elution from the cell walls.
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PMID:Site-directed mutagenesis of the catalytic residues Asp-52 and Glu-35 of chicken egg white lysozyme. 256 61

The generally accepted hypothesis that exons code for fundamental polypeptide structures was tested with a fusion protein consisting of almost the entire polypeptide coded by exon 2 of chicken lysozyme fused to the N-terminus of beta-galactosidase of E.coli. Exon 2 encodes residues 28-81 of lysozyme. It thus contains Glu 35 and Asp 52, which are essential for hydrolysis of glycosidic bonds. The exon 2-beta-galactosidase fusion protein hydrolysed the substrate 4-methylumbelliferyl-N,N',N''-triacetyl-chitotrioside with a reaction rate about 1/40,000 of that of native lysozyme. The low hydrolysis rate of exon 2-peptide is partially caused by its low affinity to its substrate.
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PMID:50 residues coded by exon 2 of chicken lysozyme carry residual catalytic activity. 264 4

The cel-3 gene cloned from Fibrobacter succinogenes into Escherichia coli coded for the enzyme EG3, which exhibited both endoglucanase and cellobiosidase activities. The gene had an open reading frame of 1,974 base pairs, coding for a protein of 73.4 kilodaltons (kDa). However, the enzyme purified from the osmotic shock fluid of E. coli was 43 kDa. The amino terminus of the 43-kDa protein matched amino acid residue 266 of the protein coded for by the open reading frame, indicating proteolysis in E. coli. In addition to the 43-kDa protein, Western immunoblotting revealed a 94-kDa membranous form of the enzyme in E. coli and a single protein of 118 kDa in F. succinogenes. Thus, the purified protein appears to be a proteolytic degradation product of a native protein which was 94 kDa in E. coli and 118 kDa in F. succinogenes. The discrepancy between the molecular weight expected on the basis of the DNA sequence and the in vivo form may be due to anomalous migration during electrophoresis, to glycosylation of the native enzyme, or to fatty acyl substitution at the N terminus. One of two putative signal peptide cleavage sites bore a strong resemblance to known lipoprotein leader sequences. The purified 43-kDa peptide exhibited a high Km (53 mg/ml) for carboxymethyl cellulose but a low Km (3 to 4 mg/ml) for lichenan and barley beta-glucan. The enzyme hydrolyzed amorphous cellulose, and cellobiose and cellotriose were the major products of hydrolysis. Cellotriose, but not cellobiose, was cleaved by the enzyme. EG3 exhibited significant amino acid sequence homology with endoglucanase CelC from Clostridium thermocellum, and as with both CelA and CelC of C. thermocellum, it had a putative active site which could be aligned with the active site of hen egg white lysozyme at the highly conserved amino acid residues Asn-44 and Asp-52.
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PMID:Structure of the cel-3 gene from Fibrobacter succinogenes S85 and characteristics of the encoded gene product, endoglucanase 3. 267 79

Three human lysozymes containing a mutation either at Asp-53 to Glu or at Tyr-63 to Trp or Phe were synthesized and examined for their immunological and enzymatical activities in comparison with the native one. All mutants were immunologically indistinguishable from native human lysozyme. The [Trp63] and [Phe63] mutants catalysed the hydrolysis of Micrococcus lysodeikticus cell wall and glycol chitin effectively, while the [Glu53] mutant displayed very low activity toward M. lysodeikticus cells and no detectable activity toward glycol chitin.
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PMID:Engineering of the active site of human lysozyme: conversion of aspartic acid 53 to glutamic acid and tyrosine 63 to tryptophan or phenylalanine. 288 Jun 6

The amino acid sequence of a lysozyme, (B-enzyme), from Bacillus subtilis YT-25 was determined by conventional methods. B-Enzyme comprised 117 amino acid residues and had a heterogeneous sequence in the amino-terminal region. The amino acid sequence of B-enzyme was different from those of all other lysozymes the sequences of which are known. However, the partial amino acid sequence of Ser(74) to Ser(97) of B-enzyme was homologous with that of the active-site region of hen egg-white lysozyme (Ser(36) to Ser(60], which includes one of the catalytic amino acids, Asp(52). It is interesting that B-enzyme has an amino acid sequence homologous with that of the gag protein p25 of the AIDS virus ARV-2.
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PMID:Amino acid sequence of a lysozyme (B-enzyme) from Bacillus subtilis YT-25. 314 18

We have developed experimental approaches for the construction of protocellular structures under simulated primitive earth conditions and studied their formation and characteristics. Three types of envelopes; protein envelopes, lipid envelopes, and lipid-protein envelopes are considered as candidates for protocellular structures. Simple protein envelopes and lipid envelopes are presumed to have originated at an early stage of chemical evolution, interaction mutually and then evolved into more complex envelopes composed of both lipids and proteins. Three kinds of protein envelopes were constructed in situ from amino acids under simulated primitive earth conditions such as a fresh water tide pool, a warm sea, and a submarine hydrothermal vent. One protein envelope was formed from a mixture of amino acid amides at 80 degrees C using multiple hydration-dehydration cycles. Marigranules, protein envelope structures, were produced from mixtures of glycine and acidic, basic and aromatic amino acids at 105 degrees C in a modified sea medium enriched with essential transition elements. Thermostable microspheres were also formed from a mixture of glycine, alanine, valine, and aspartic acid at 250 degrees C and above. The microspheres did not form at lower temperatures and consist of silicates and peptide-like polymers containing imide bonds and amino acid residues enriched in valine. Amphiphilic proteins with molecular weights of 2000 were necessary for the formation of the protein envelopes. Stable lipid envelopes were formed from different dialkyl phospholipids and fatty acids. Large, stable, lipid-protein envelopes were formed from egg lecithin and the solubilized marigranules. Polycations such as polylysine and polyhistidine, or basic proteins such as lysozyme and cytochrome c also stabilized lipid-protein envelopes.
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PMID:Construction of protocellular structures under simulated primitive earth conditions. 322 17

A T4 lysozyme-coding DNA sequence of 495 bp was chemically synthesized and cloned by ligation of 26 deoxyribooligonucleotide fragments in two steps with a linearized plasmid followed by transformation. On selection by colony hybridization and DNA sequence analysis, clone pTLY.10 was identified to contain a complete T4 lysozyme synthetic DNA. On expression under lac-promoter, unfused T4 lysozyme was obtained in approximately 4-6% yield. The design and synthesis of two putative folding mutants, flexible (Gly-Gly-Gly) and rigid (Asn-Asp-Gly) at position 73-74-75, were based on hierarchical principles. Both mutants lost enzymatic activity of the wildtype. These results are readily understandable if the hierarchical organization of the structure is taken into account. A possible explanation is that the catalytic sites are blocked in both mutants.
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PMID:Hierarchical strategy for protein folding and design: synthesis and expression of T4 lysozyme gene and two putative folding mutants. 333 99

The chemical shift changes observed in the carbon-13 NMR spectra of the carboxylate region in conjunction with previous fluorescence data indicate that mercury and lead bind to both disulfide bridge 64-80 and to Asp-52 in hen egg-white lysozyme. Methylmercury appears to bind primarily to the disulfide linkage. The carbon-13 NMR results support previous investigations by halide ion NMR and x-ray crystallography. The combined information from all of these techniques is useful for providing a clearer description of heavy metal binding to proteins.
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PMID:The detection of mercury, lead, and methylmercury binding sites on lysozyme by carbon-13 NMR chemical shifts of the carboxylate groups. 337 92


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