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)

Estrone glucuronide conjugates of hen egg white lysozyme were prepared by both the mixed-anhydride and active-ester coupling procedures. Both methods gave good yields of conjugate but the active-ester procedure gave a more diverse range of products consistent with a greater acylating ability. Unreacted lysozyme which was present in all cases was removed by a combination of cation-exchange chromatography on a Pharmacia Mono-S column and hydrophobic-interaction chromatography on an Alkyl Superose column. The conjugate families were more hydrophobic than native lysozyme. The chromatographic behaviour of the reaction mixtures on Mono S columns under non-denaturing conditions was complex as a result of hydrophobic effects and only at pH values above 7.0 did the conjugates elute in the order of their overall charges. At pH values below 6.0 the conjugates, although less charged than lysozyme, eluted last on salt gradients. In contrast when denaturing 7 M urea buffers were used the conjugates eluted in the order of their electrostatic charges and reproducible patterns were obtained which served as an excellent analytical system for lysozyme-steroid glucuronide conjugates. The purified conjugate material from the active-ester reaction gave over 90% inhibition of the lytic activity in the presence of an estrone glucuronide antibody. When used in a homogeneous enzyme immunoassay system the levels of urinary estrone glucuronide encountered in a normal menstrual cycle were easily measured.
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PMID:Use of ion-exchange and hydrophobic-interaction chromatography for the rapid purification of lysozyme-estrone glucuronide conjugates. 789 91

The adsorption isotherms of different proteins from aqueous solution to the surface of different solids have been compared in the presence of additives such as urea, surfactants and high concentration of various neutral salts. The adsorption isotherms of lysozyme on alumina are not affected much in the presence of 8 M urea showing the rigid structure of lysozyme whereas isotherms of hemoglobin show surface coagulation even in presence of 2 M urea. In presence of 8 M urea, adsorption isotherms of BSA on alumina show two distinct steps. The extent of protein adsorption in the presence of surfactants depends on the nature of surfactants as well as of the underlying surface. The adsorption isotherms of BSA and lysozyme in presence of 2 M concentration of different neutral salts have also been compared with each other. In the presence of denaturants such as NaI and LiCl, the proteins are adsorbed in unfolded beta-conformation whereas in the presence of protein stabilizers such as NaCl, KCl and Na2SO4, amount of protein adsorbed at saturation is zero or extremely small showing that unfolding of proteins at the interface is necessary for initial stage of protein adsorption. The standard free energy change (delta G degrees) per square meter of the surface, signifying relative affinity of adsorption at the state of monolayer saturation, have been calculated. The magnitude of standard free energy of transfer (delta G degrees B) of one mole of protein to the surface in presence of all the additives was found close to 40 kJ/mole.
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PMID:Effect of denaturants and stabilisers on protein adsorption at solid-liquid interfaces. 792 31

The effect of urea on the crystal structure of hen egg-white lysozyme has been investigated using X-ray crystallography. High resolution structures have been determined from crystals grown in the presence of 0, 0.7, 2, 3, 4, and 5 M urea and from crystals soaked in 9 M urea. All the forms are essentially isomorphous with the native type II crystals, and the derived structures exhibit excellent geometry and RMS differences from ideality in bond distances and angles. Comparison of the urea complex structures with the native enzyme (type II form, at 1.5 A resolution) indicates that the effect of urea is minimal over the concentration range studied. The mean difference in backbone conformation between the native enzyme and its urea complexes varies from 0.18 to 0.49 A. Conformational changes are limited to flexible surface loops (Thr 69-Asn 74, Ser 100-Asn 103), the active site loop (Asn 59-Cys 80), and the C-terminus (Cys 127-Leu 129). Urea molecules are bound to distinct sites on the surface of the protein. One molecule is bound to the active site cleft's C subsite, at all concentrations, in a fashion analogous to that of the N-acetyl substituent of substrate and inhibitor sugars normally bound to this site. Occupation of this subsite by urea alone does not appear to induce the conformational changes associated with inhibitor binding.
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PMID:A structural basis for the interaction of urea with lysozyme. 800 89

Protein disulfide isomerase (PDI) catalyzes the formation and rearrangement of disulfide bonds during protein folding. PDI coupled to cyanogen bromide-activated agarose retains its catalytic activity, and a column of this material increases both the rate and the yield for folding disulfide-containing proteins. For reduced, denatured ribonuclease, the overall yield of fully active ribonuclease isolated from the PDI column in one pass was 85-98% of the applied protein. Under the same conditions in the absence of PDI, ribonuclease regained only 16% of its native activity. The oxidative folding of reduced denatured lysozyme is complicated by aggregation so that in the absence of PDI optimal yields of only < or = 25% are obtained at lysozyme concentrations of 1.6 mg/ml. When reduced, denatured lysozyme (1.6 mg/ml) is passed over a PDI column in 1-2 M urea in the presence of a glutathione redox buffer, the specific activity of the recovered lysozyme is identical to that of the native enzyme and the total recovery of the applied protein is 50-65%.
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PMID:Catalysis of protein folding by agarose-immobilized protein disulfide isomerase. 805 46

The amide hydrogen exchange behaviour of hen egg-white lysozyme denatured in 8 M urea has been studied at pH 2.0, 20 degrees C. The observed exchange rates have been compared with those predicted for the same residues in a random coil conformation using recently published parameters for side-chain inductive and temperature effects on exchange catalysis. The protection factors for exchange obtained in this way were found to be close to unity, with 41 of the 61 residues that could be followed having protection factors less than 2. No protection factor was greater than 5. In addition, previous data for hen lysozyme denatured thermally and for a three-disulphide derivative, CM6-127 lysozyme, denatured at pH 2.0 have been reanalysed using the new reference parameters, and the protection factors were found to be similar to those of hen lysozyme denatured in 8 M urea. Thus, although 1H NMR and far UV CD spectroscopy suggest that considerable deviations from random coil behaviour occur in these denatured states, such residual structure is insufficient to protect amide hydrogens significantly against exchange. This behaviour contrasts with that of a partly folded state of hen lysozyme denatured in trifluoroethanol and with that of the molten globule state of a homologous protein, guinea pig alpha-lactalbumin. Here protection factors for many amide hydrogens exceed 30 and belong to residues located in continuous regions of the amino acid sequence, indicating the presence of persistent structure. The study of hydrogen exchange in substantially denatured states of a protein, therefore, provides a basis for the interpretation of protection factors in partially folded states.
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PMID:Amide hydrogen exchange in a highly denatured state. Hen egg-white lysozyme in urea. 814 39

Acid-soluble extract of rabbit bladder mucosa was obtained by washing out the bladder of normal female New Zealand rabbit with 1% acetic acid in the presence of proteinase inhibitors. Acid urea polyacrylamide electrophoresis (AU-PAGE) analysis indicated that the extract had more than 10 main protein bands. The currently-known antibiotic peptides, e. g. lysozyme and defensin-like molecules were not found in this material. When tested for antibacterial activity by using ultrasensitive radial diffusion assay, the acid-soluble extract effectively killed E. coli ML-35P. The gel overlay assay showed that the anti-bacterial activity of the acid-soluble extract was relevant to two protein bands referred to as rabbit bladder protein 1 (Rab BP-1) and rabbit bladder protein 2 (Rab BP-2). The Rab BP-1 and Rab BP-2 accounted for 2.5% and 1.2% of the total acid-soluble extract proteins, respectively. These results suggest that the long recognized ability of the normal rabbit bladder wall to kill adherent E. coli may result from the presence of endogenous antibacterial proteins associated with its mucosa.
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PMID:[Study on antibacterial proteins from rabbit bladder mucosa]. 815 Apr 30

Denaturations of ribonuclease A, lysozyme, and cytochrome c by guanidine hydrochloride (GdnHCl), urea, and GdnHCl-urea mixture were studied at constant temperature and pH to assess the functional dependence of denaturational free energy change (delta GD) on denaturant concentration over an extended GdnHCl concentration range. Conventional analysis of GdnHCl-induced transition curve exhibits a linear plot of delta GD versus [GdnHCl] in the transition zone. To extend delta GD measurements beyond this narrow concentration range, GdnHCl-induced unfolding was measured in the presence of different concentrations of urea. delta GD values from these measurements were corrected for the effect of urea on the free energy change using the appropriate relation. The corrected delta GD data were mapped onto the delta GD versus [GdnHCl] plot. For each protein, the dependence of free energy change on denaturation was found to be linear over the full GdnHCl concentration.
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PMID:A new method for testing the functional dependence of unfolding free energy changes on denaturant concentration. 820 82

Fast protein size-exclusion liquid chromatography (SEC-FPLC) was used to study solvent-induced unfolding of six proteins. Two of them (sperm whale myoglobin and hen white lysozyme) denature on the simple N (native)<-->U (completely unfolded) scheme. The other four proteins [bovine and human alpha-lactalbumin, bovine carbonic anhydrase B (BCAB), and beta-lactamase from Staphylococcus aureus] denature through the molten globule (MG) state (i.e., on the N<-->MG<-->U denaturation scheme). We have shown that the permeation properties of the Superose 12 columns are practically independent of temperature, pH, and denaturants in wide concentration intervals. In the case of myoglobin and lysozyme denaturation at 4 degrees C (when the exchange between the native and unfolded states is slower than the characteristic time of chromatography), a bimodal distribution on molecular dimensions in the transition region was observed. This indicates that, under denaturant action, protein molecules can only be in one of the two states with different compactness. In other words, this shows that FPLC is one of the most direct approaches to establish the "all-or-none" mechanism of the equilibrium solvent-induced denaturation of globular proteins. The curves of guanidinium hydrochloride- (GdmHCl) or urea-induced unfolding (N<-->U or MG<-->U transitions) of a protein on a column (monitored either by the relative areas of two peaks or--for fast exchange--by the position of the average peak) coincide with those monitored by far-UV CD in solution. The Stokes radius values obtained with the use of FPLC for the molten globule states of BCAB (1.6 M GdmHCl in 0.1 M sodium phosphate, pH 6.8, and acid form at pH 3.6) and for the human alpha-lactalbumin molten globule (2.0 M GdmHCl in 0.1 M sodium phosphate, pH 6.8) coincide with those known from literature. Thus, it has been shown that fast protein size-exclusion liquid chromatography (FPLC) is an "inert" technique, i.e., it does not shift the equilibrium between N, MG, and U states and, therefore, can be used for qualitative and quantitative studies of protein denaturation.
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PMID:Use of fast protein size-exclusion liquid chromatography to study the unfolding of proteins which denature through the molten globule. 824 Nov 85

The amino acid replacement Asn101-->Asp in the T4 phage lysozyme was obtained by site-directed mutagenesis and the plasmid mutant protein expression was constructed. Though the mutant protein circular dichroism (CD) spectrum is virtually unchanged as compared with the wild type protein and the enzymatic activity is 90% of that of the wild type protein, the stability of this mutant to urea-induced unfolding decreases and two stages in the denaturation process are observed.
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PMID:[The effect of point amino acid substitutions on the stability of phage T4 lysozyme. I. Asn101---Asp substitution]. 836 62

Surface hydrophobicity has recently been emphasized as an important parameter for functional correlation of proteins. However, evaluations of the parameter by different experimental techniques often do not correlate well with each other. In this paper we have compared surface hydrophobicity of a basic protein with those of beta-lactoglobulin, ovalbumin and lysozyme by fluorescence probe method using ANS as an external probe. Two different fluorimetric approaches to determining the surface hydrophobicity parameter, namely, the slope method and the binding parameter method, follow the same relative order. Denaturants, urea, and guanidine hydrochloride disrupted the hydrophobic clefts of the inhibitor on the surface, causing a drastic reduction of surface hydrophobicity.
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PMID:Surface hydrophobicity of a low molecular weight basic trypsin subtilisin inhibitor from marine turtle eggwhite. 837 Jun 71


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