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

---

Query: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used optically detected magnetic resonance (ODMR) to characterize the degree of solvent availability of the tryptophan residues in lysozyme that are likely to be responsible for the observed phosphorescence. From the phosphorescence spectra, ODMR zero-field splittings (zfs), and ODMR line widths, we concur with the X-ray structure [Blake, C. C., Mair, G. A., North, A. C. T., Phillips, D. C., & Sarma, V. R. (1967) Proc. R. Soc. London, ser. B 167, 365-377] that Trp-62 behaves as an exposed residue and Trp-108 is buried. In addition, we present evidence that ODMR can be used in conjunction with conventional phosphorescence to evaluate the degree of order in the microenvironments of tryptophan in a protein containing several tryptophans. By the specific modification of residues Trp-62 and Trp-108, we have identified those portions of the ODMR lines in the native enzyme that are due to those specific residues. Barring major enzyme conformational changes in the vicinity of unmodified tryptophan residues when Trp-62 or Trp-108 are selectively modified, we find that Trp-108 dominates both the phosphorescence and the ODMR signals in native lysozyme. The results are discussed in view of previous fluorescence findings.
...
PMID:Triplet state of tryptophan in proteins. 2. Differentiation between tryptophan residues 62 and 108 in lysozyme. 44 57

Though DNase does not contain any cysteine residues, incubation of the enzyme with 2-nitro-5-thiocyanobenzoic acid in the presence of Ca2+ at pH values above 7.5 results in an irreversible inactivation of the enzyme. The inactivation also occurs when Ca2+ is replaced by Mg2+, but not in their absence. Amino acid analyses after acid hydrolyses of the completely inactivated ant the native enzymes show no significant differences in composition, including tryptophan and half-cystine residues. However, sodium dodecyl sulfate gel electrophoresis indicates enzyme cleavage by the treatment with 2-nitro-5-thiocyanobenzoic acid. This reagent does not inactivate chymotrypsin and lysozyme, and under conditions where bovine DNase is inactivated, does not inactivate other nucleases such as ribonuclease, snake venom phosphodiesterase, and spleen acid DNase. However, it inactivates malt DNase and can, therefore, be considered a specific inhibitor of DNase I. The inactivation kinetics is pseudo-first order, resembling Michaelis-Menten, with an affinity constant of 16.7 mM. It is the cyano group, not the thionitrobenzoic acid of 2-nitro-5-thiocyanobenzoic acid that reacts to form cyano-DNase.
...
PMID:Inactivation of bovine pancreatic DNase by 2-nitro-5-thiocyanobenzoic acid. I. A novel inhibitor for DNase I. 48 54

Optical detection of magnetic resonance (ODMR) has been employed to examine the homogeneity of the tryptophan environment, both of the isolated residue in solvent, and of tryptophan in glucagon and lysozyme and azurin B (Pseudomonas aeruginosa). From the shifts in the zero-field splittings, we can safely conclude that tryptophan in lysozyme, azurin B, or glucagon does not have the same type of solvent interaction as the free residue. However, by "burning holes" in the OSMR lines, it is evident that the lines in these cases are inhomogeneously broadened. From the relative line widths and hole widths, it appears that ODMR can be used to examine the relative diversity of interactions for a luminescent amino acid in a protein. We have followed the ODMR line characteristics in a progression from free N-acetyl-L-tryptophanamide, to tryptophan in lysozyme, to "denatured" lysozyme, and present evidence that the line widths narrow as the tryptophan residues become less solvent accessible.
...
PMID:Triplet state of tryptophan in proteins: the nature of the optically detected magnetic resonance lines. 62 48

A new double-labelling procedure for amino acid analysis which requires only routine chromatographic equipment is described. When 1-fluoro-2,4-dinitro[3H]benzene is reacted with a mixture of 14C-labelled amino acids followed by reaction with the same 14C-labelled amino acid mixture diluted with an unlabelled sample of amino acids, the 3H:14C ratio in the resulting 2,4-dinitrophenyl (DNP) amino acid derivatives of the diluted sample will be increased in proportion to the quantity of unlabelled amino acid in the diluted sample. This procedure gave reliable results when applied to the known proteins insulin and lysozyme. The procedure is most advantageous when applied to amino acids which are unstable during acid hydrolysis or present in low molar fractions. When applied to the analysis of the bacteriorhodopsin in Halobacterium cutirubrum, this procedure showed the presence of one histidine residue and four tryptophan residues per mole protein but no cystine or cysteine; in general, the analyses obtained were consistent with those originally reported by Oesterhelt, D. and Stoeckenius, W. (1971) (Nature (London) New Biol. 233, 149-152) for bacteriorhodopsin of H. halobium.
...
PMID:A new double-labelling procedure for determination of amino acid composition: application to bacteriorhodopsin. 66 97

The binding of beta-methyl N-acetylglucosaminide (betaMeGlcNAc) to egg-white lysozyme of hen in the tetragonal crystal form was studied by X-ray diffraction techniques to a resolution of 0.25 nm. The binding of the beta-methyl glycoside is almost identical with the binding of beta-N-acetylglucosamine (betaGlcNAc). Real-space refinement of the lysozyme-alpha/beta GlcNAc and lysozyme-betaMeGlcNAc complexes allowed preliminary analysis of the conformational changes observed on binding monosaccharide inhibitors, specially in the region involving tryptophan-62 and residues 70--76. Tetagonal lysozyme crystals, grown in the absence of acetate ions, were examined by X-ray diffraction to 0.25nm resolution. The resulting difference Fourier synthesis shows no firm evidence for bound acetate ions and indicates only minor conformational changes in the side-chain positions of aspartic acid-101 and asparagine-103. The close similarity of the lysozyme structures in the presence and absence of acetate is contrary to expectations from previous n.m.r. studies.
...
PMID:Crystal structures of egg-white lysozyme of hen in acetate-free medium and of lysozyme complexes with N-acetylglucosamine and beta-methyl N-acetylglucosaminide. 69 38

Reaction of alpha-lactalbumin at pH 7 in aqueous solution with either 2-hydroxy-5-nitrobenzylbromide or N-bromosuccinimide yields derivatives in which only 2 of the 4 tryptophan residues are modified. All 4 residues of tryptophan are modified under the similar conditions in 8 M urea. Structural analysis of the modified derivatives revealed that tryptophans 26 and 118 are the sole reactive residues and that tryptophan 118 reacts more rapidly than tryptophan 26. The fluorescence of alpha-lactalbumin modified to varying extents with N-bromosuccinimide indicates that tryptophan 118 is exposed to solvent whereas tryptophan 26 is in a more hydrophobic environment. The chemical reactivities and fluorescence properties of tryptophans 26 and 118 are consistent with the proposed conformations of alpha-lactalbumin based on its similarity with egg white lysozyme. The kinetic properties of both derivatives of alpha-lactalbumin containing up to 2 modified residues indicate that each derivative has decreased affinity for the galactosyltransferase but that at saturating concentrations, Km and Vmax for lactose synthesis are unchanged from those of native alpha-lactalbumin.
...
PMID:Modification of bovine alpha-lactalbumin with N-bromosuccinimide and 2-hydroxy-5-nitrobenzylbromide. 80 37

Two major proteins, termed proteins A and B, and one minor species, termed protein C, have been purified to homogeneity from dilute acid extracts of dormant spores of Bacillus megaterium. These three species comprise approximately 80% of the protein in the dilute acid extracts and account for 60 to 75% of the protein degraded during spore germination. All three proteins have low molecular weights (7,000 to 10,000), high isoelectric points (greater than 9.8), alanine as the NH2-terminal amino acid, are more hydrophilic than most proteins, and all lack cysteine, cystine, and tryptophan. In addition all three proteins are extremely sensitive to a wide variety of proteolytic enzymes, much more so than "average" proteins such as serum albumin, lysozyme, and hemoglobin. These proteins also bind to both purified DNA and to a nuclear body from dormant spores. Although this binding gives little or no protection to proteins A and B from proteolysis, it does result in elevation of the melting temperature of the DNA by as much as 20degrees.
...
PMID:Purification and properties of some unique low molecular weight basic proteins degraded during germination of Bacillus megaterium spores. 80 43

The chemical modification of tryptophan residues of hen egg-white lysozyme by N-bromosuccinimide (NBS) was studied kinetically by the stopped-flow method, monitoring changes in absorbance and fluorescence. One most rapidly reacting tryptophan residue, probably Trp 62, was clearly distinguished from four other residues in terms of rate of modification. This residue was protected by ethylene glycol chitin, N-acetyl glucosamine (NAG), and tri-NAG, but not by gluconolactone. The dissociation constant Kd of the enzyme-ligand complex was obtained from the protection effects. These results are in good agreement with results previously obtained.
...
PMID:Kinetic studies on the chemical modification of lysozyme by N-bromosuccinimide and its protection by substrates and analogs. 89 64

Two mutants of phage T4 lysozyme were prepared and characterized. One mutation substituted a tyrosine residue for tryptophan at position 138. The other substituted tyrosines at all three tryptophan positions of the wild type molecule (126, 138, 158). Comparative studies of the physical properties (absorption, fluorescence, circular dichroism) of the three enzymes were performed as a function of pH. Also, the proteins were reversibly melted as a function of pH. Since the unfolding reaction appeared to be a two-state process for all these proteins, the data were analyzed by the van 't Hoff procedure. The changes in stability and activity produced by substitution of Trp 138 were especially significant. The other substitutions were neutral. See the end of the paper for a summary of conclusions. In the appendix the appropriate thermodynamic relations are developed for a constant deltaCp transition.
...
PMID:Stability of phage T4 lysozymes. I. Native properties and thermal stability of wild type and two mutant lysozymes. 91 78

The position of a single N'-formylkynurenine residue in ozone-inactivated hen egg-white lysozyme [EC 3.2.1.17] was determined by two methods. One involved identification of an amino-terminus of the C-peptide obtained by selective cleavage with hydrazine of the kynurenyl peptide linkage in oxidized lysozyme. The other was to analyze a tryptic peptide containing kynurenine in the modified enzyme. Both methods showed that tryptophan 62 in lysozyme was so sensitive to ozone as to be selectively oxidized to N'-formylkynurenine with concomitant loss of the lytic activity.
...
PMID:Identification of tryptophan 62 as an ozonization-sensitive residue in hen egg-white lysozyme. 93 60


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

---