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)

Primary amines react with 2,4-pentanedione at pH 6-9 to form enamines, N-alkyl-4-amino-3-penten-2-ones. The latter compounds readily regenerate the primary amine at low pH or on treatment with hydroxylamine. Guanidine and substituted guanidines react with 2,4-pentanedione to form N-substituted 2-amino-4,6-dimethylpyrimidines at a rate which is lower by at least a factor of 20 than the rate of reaction of 2,4-pentanedione with primary amines. Selective modification of lysine and arginine side chains in proteins can readily be achieved with 2,4-pentanedione. Modification of lysine is favored by reaction at pH 7 or for short reaction times at pH 9. Selective modification of arginine is achieved by reaction with 2,4-pentanedione for long times at pH 9, followed by treatment of the protein with hydroxylamine. The extent of modification of lysine and arginine side chains can readily be measured spectrophotometrically. Modification of lysozyme with 2,4-pentanedione at pH 7 results in modification of 3.8 lysine residues and less than 0.4 arginine residue in 24 hr. Modification of lysozyme with 2,4-pentanedione at pH 9 results in modification of 4 lysine residues and 4.5 arginine residues in 100 hr. Treatment of this modified protein with hydroxylamine regenerated the modified lysine residues but caused no change in the modified arginine residues. One arginine residue seems to be essential for the catalytic activity of the enzyme.
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PMID:Modification of arginine and lysine in proteins with 2,4-pentanedione. 0 43

Standard functions of enthalpy, entropy and the Gibbs energy of native and denatured lysozyme in the range of 0-100 degrees C and pH 1.5-7.0 are represented in three-dimensional projections. The denaturational Gibbs energy change reaches 16 kcal mol-1 at conditions of maximal protein stability (0 degrees C, pH 4.5-7.0) and equals 14.5 kcal mol-1 at 25 degrees C and neutral pH. This result was found to be in agreement with the data reported from guanidine hydrochloride denaturation studies. Partial thermodynamic functions of the conformational and ionizational changes of the protein are obtained from entropy and Gibbs-energy changes in denaturation. The conformational partial entropy and Gibbs-energy change are found to be independent of pH. The pH-dependent partial ionizational entropy and Gibbs-energy changes are induced by normalization of the ionization behaviour of buried groups and cause a decrease of protein stability.
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PMID:Thermodynamic investigations of proteins. III. Thermodynamic description of lysozyme. 0 48

The reversible unfolding of alpha-lactalbumin by guanidine hydrochloride, was studied at 25.0 degrees C in a relatively low concentration range of the denaturant (0.80-2.00 mol/l) by means of difference spectra and pH-jump measurements. The unfolding was shown to occur between two states, N and D, because apparent rate-constants of the unfolding and the refolding reactions depended only on pH. All curves plotted as the logarithmical equilibrium constant log KD against pH could fall on the same base curve by shifting each curve along the log KD axis. From the dependence of the logarithmic rate constant on pH, master curves could also be made for the forward and the backward reactions. The dependence of these master curves on pH indicates that the groups affecting the pH dependence of the unfolding are three residues with pKN = 3.3 and pKA = pKD = 4.4, one residue with pKN = pKA = 3.8 and pKD = 4.4, and one residue with pKN = 5.8 and pKA = pKD = 6.3, where A indicates the activated state. On the other hand, from the denaturant activity dependence of the shift factors required for making the master curves, the value of the intrinsic binding constant of the denaturant to the protein was found to be similar to that obtained from previous measurements at pH 5.5. Differences between the numbers of the binding sites of the denaturant on the denaturated and the native proteins, and between those on the activated and the native proteins were shown to be 5.3 and 2.1, respectively. The free energy of stabilization in the native-like environment also shows that the protein in the native state is more unstable than lysozyme.
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PMID:Equilbrium and kinetics of the unfolding of alpha-lactalbumin by guanidine hydrochloride (II). 0 10

Using lysozyme-lysate of Micrococcus lysodeikticus cell wall coupled with Sepharose, several bacteriolytic enzymes were purified from crude preparations of animal and microbial origin. Quail egg-white, human milk and salivary lysozymes [EC 3.2.1.17] were adsorbed onto the adsorbent at pH 5-7 and eluted with 2M NaCl at pH 10. By means of these treatments, lysozymes were purified 20-250 fold with activity recoveries of 60-80%, and the quail lysozyme thus purified was shown to be discelectrophoretically homogeneous. Some bacteriolytic enzymes of microbial origin were also highly purified by using this affinity adsorbent. A bacterial lysozyme from Bacillus sp. ML-208 showed high affinity for the ligand and was not eluted under the conditions mentioned above, but was recovered by elution with 2M guanidine-HCl at pH 5.8, resulting in a 500-fold increase in the specific activity. A Pseudomonas-lytic enzyme from Streptomyces sp. P-51 was easily released from the adsorbent by elution with 0.5M NaCl at pH 5.0. A staphylolytic F2 enzyme from S. griseus S-35 and a chitinase [EC 3.2.1.14] from yam, both of which were completely inert toward M. lysodeikticus cell wall, passed through the adsorbent column. A modified ligand, in which muramic acid and glucosamine residues were N,O-acetylated, failed to adsorb any of these animal and bacterial lysozymes. Some of the enzymatic properties and bacteriolytic action spectra of these purified enzymes are also described in this paper in comparison with those of hen egg-white lysozyme.
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PMID:Purification of several bacteriolytic enzymes by affinity chromatography on lysozyme-lysate of Micrococcus lysodeikticus cell wall coupled with sepharose. 0 36

Mycobacterium ulcerans produces an exotoxin in culture which, when inoculated into guinea pig skin, causes inflammation, necrosis, edema, and other histopathological changes resembling those in infections of humans. The toxin was resistant to heat and to alkalies and was moderately acid labile. Toxic activity was destroyed by Pronase, phospholipase, lipase, amylase, and glucosidase but not by trypsin, collagenase, cellulase, lysozyme, hyaluronidase, or neuraminidase. Toxic activity was resistant to treatment with 2-mercaptoethanol, urea, guanidine hydrochloride, p-chloromercuribenzoate, ethylenediaminetetraacetate, and sodium deoxycholate but was destroyed by sodium m-periodate and sodium dodecyl sulfate. The toxin was precipitated by a wide range of ammonium sulfate concentrations. Extraction with chlorofrom-methanol or petroleum ether destroyed its activity. Isopycnic density gradient ultracentrifugation in KBr produced a high-density lipoprotein layer with a 24-fold increase in specific activity. The results indicate that this toxin is a high-molecular-weight phospholipoprotein-polysaccharide complex.
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PMID:Further characterization of Mycobacterium ulcerans toxin. 3 Jun 94

An ADP-ribosyltransferase was purified approximately 500-fold from the supernatant fraction of turkey erythrocytes. The enzyme hydrolyzed [carbonyl-(14)C]NAD to ADP-ribose and [carbonyl-(14)C]nicotinamide at a low rate. Nicotinamide formation from NAD was enhanced by arginine methyl ester > D-arginine approximately L-arginine > guanidine; lysine, histidine, and citrulline were ineffective. Incubation of [adenine-U-(14)C]NAD and arginine methyl ester or arginine with the purified enzyme resulted in the formation of new compounds that contained (14)C, reacted with ninhydrin, and quenched background fluorescence of thin-layer plates viewed in ultraviolet light. Their mobilities on thin-layer chromatograms were indistinguishable from those of ADP-ribosylarginine methyl ester and ADP-ribosylarginine formed during incubation of choleragen with NAD and arginine methyl ester or arginine, respectively [Moss, J. & Vaughan, M. (1977) J. Biol. Chem. 252, 2455-2457]. The purified transferase also catalyzed the incorporation of label from [adenine-(14)C]-NAD into lysozyme, histones and polyarginine. When the (14)C-labeled lysozyme was incubated with snake venom phosphodiesterase, the radioactivity was released and, on thin-layer chromatograms, exhibited a mobility indistinguishable from that of 5'-AMP, as would be expected of an ADP-ribosylated protein, but not of a poly(ADP-ribosylated) product. The purified transferase activated rat brain adenylate cyclase and, as is the case with choleragen, activation was absolutely dependent on NAD. The presence in the avian erythrocyte of a protein that, like choleragen and Escherichia coli heat-labile enterotoxin, apparently activates adenylate cyclase and possesses ADP-ribosyl transferase activity is consistent with the view that the mechanisms through which the bacterial toxins produce pathology are not entirely foreign to vertebrate cells, at least some of which may possess and employ an analogous mechanism for activation of adenylate cyclase.
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PMID:Isolation of an avian erythrocyte protein possessing ADP-ribosyltransferase activity and capable of activating adenylate cyclase. 21 2

Phage T4 lysozyme has been used extensively in studies of the genetic code. However, little work has been done on the characterization of the purified enzyme. Therefore, we determined the spectral properties of native T4 lysozyme and used these properties to follow the unfolding transition. The ultraviolet absorption spectrum and solvent perturbation difference spectrum indicate that the aromatic amino acids are extensively exposed to solvent. The CD and ORD spectra are characteristic of a high fraction of helix. Guanidine hydrochloride denaturation results show that over a T4 lysozyme concentration range of 0.07-1 g/l the c-m equals 2.7 M guanidine hydrochloride at pH 5 and that the transition is 100% reversible as judged by enzymatic assay and four different spectrophotometric criteria: CD at 295 nm, CD at 223 nm, fluorescence intensity at 350 nm and wavelength of maximum fluorescence. Guanidine hydrochloride denaturation at pH 2.5 was followed using fluorescence emission and has a c-m equals 1.7 M guanidine hydrochloride, indicating a strong pH dependence of chemical unfolding. Reversible thermal denaturation conditions were located at acid pH, 0.2 M NaCl, 10-4 M dithiothreitol and 10-6 M T4 lysozyme. The CD signal at 223 nm was used to measure the unfolding. Thermodynamic analysis of the thermal data showed an increase in T-m, increment H-unf and increment S-unf with increasing pH.
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PMID:Phage T4 lysozyme. Physical properties and reversible unfolding. 23 26

The second derivative absorption spectra of serum albumin, insulin, ribonuclease and lysozyme were measured under various conditions to determine the state and amount of their phenylalanine residues. The second derivative spectra of these proteins were very similar to that of phenylalanine in the region between 245 and 270 nm where tryptophan and tyrosine residues caused no appreciable interference. Denaturation of proteins with urea or guanidine hydrochloride caused decrease in the intensity of the second derivative spectra, but scarcely affected the positions of peaks and troughs. The amounts of phenylalanine residues in proteins calculated from a second derivative spectra of denatured proteins coincided well with those reported in the literature. The states of the phenylalanine residues in the proteins could be deduced from the change in optical intensity on denaturation.
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PMID:Estimation of state and amount of phenylalanine residues in proteins by second derivative spectrophotometry. 39 35

The thermal denaturation of lysozyme was studied at pH 2 in aqueous mixtures of methanol, ethanol, and 1-propanol by high sensitivity differential scanning calorimetry (DSC). The most obvious effect of alcohols was the lowering of Td, the temperature of denaturation, increasingly with higher alcohol concentration and longer alkyl chain. Both the calorimetric and van't Hoff enthalpies of denaturation initially increased and then decreased with increasing alcohol concentration, the ratio of the two enthalpies being nearly unity, 1.007 +/- 0.011, indicating the validity of the two-state approximation for the unfolding of lysozyme in these solvent systems. The reversibility of the denaturation was demonstrated by the reversibility of the DSC curves and the complete recovery of enzymic activity on cooling. The changes in heat capacity on unfolding decreased with increasing alcohol concentration for each alcohol. Experimentally determined values of denaturation temperature and of entropy and heat capacity changes were used to derive the additional thermodynamic parameters delta G degrees and delta S degrees for denaturation as a function of temperature for each alcohol--water mixture. Comparison of the thermodynamic parameters with those reported [Pfeil, W., & Privalov, P.L. (1976) Biophys. Chem. 4, 23--50] in aqueous solution at various values of pH and guanidine hydrochloride concentration showed that these latter changes have no effect on the heat capacity changes, whereas the addition of alcohols causes a sharp decrease.
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PMID:Thermodynamics of the denaturation of lysozyme in alcohol--water mixtures. 42 7

Guanidine hydrochloride (GdnHCl) and urea denaturations of lysozyme have been observed at various temperatures by measuring changes in fluorescence. Both transitions appear to be two state, with GdnHCl almost twice as effecitve a denaturant as urea for this protein. By plotting the denaturant concentrations at midpoint of the transition vs. the experimental temperature, it can be demonstrated that urea-denatured lysozyme does not obtain the degree of unfolding found in lysozyme denatured by GdnHCl.
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PMID:Comparison of temperature effect on the guanidine hydrochloride and urea denaturations of lysozyme. 53 98


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