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 circular dichroism spectra of hen egg white lysozyme, and of lysozyme derivatives in which tryptophan residues 62 or 108, or both, are selectively oxidized, have been measured as a function of pH over the range of 200 to 310 nm. Neither Trp-62 nor Trp-108 is principally responsible for the positive rotational strength in the 280 to 300 nm region. The spectrum in the 200 to 230 nm region is nearly the same in the native protein and in the derivatives, and is little affected by binding of saccharide. These results are used to reinterpret the circular dichroism spectra of the lysozymes and alpha-lactalbumins.
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PMID:The circular dichroism of lysozyme. 117 68

The ability of aromatic tryptophyl and tyrosyl side-chain donors to form charge-transfer (CT) complexes with the acceptor 1-methyl-3-carbamidopyridinium chloride has been used to investigate the degree of exposure of these aromatic residues in denaturated proteins. The coplanar geometry of the CT complexes requires that virtually a full ring face of the donor be available for interaction with the acceptor, and the aromatic donor residues of lysozyme, trypsin, chymotrypsin, and the zymogens of the latter two enzymes do not appear to be wholly "exposed" in 6 M guanidine hydrochloride. Comparison of the CT proerties of the proteins with the corresponding properties of model complexes suggests that the incomplete exposure is due at least in part to statistical fluctuations in the continuously mobile, randomly coiled polypeptide chain which result in residues being alternately fully exposed and partly covered. Reduction and alkylation of the disulfide cross-links increase the apparent availability of the aromatic residues but the exposure is still less than that expected from a comparable mixture of tryptophan and tyrosine residues. Previous studies on the exposure of the aromatic residues of lysozyme and trypsin in aqueous salt solutions, when taken together with the present results, further suggest that there are two distinct kinds of surface environment possible on native proteins in solution. Some residues appear to be located in areas of the protein surface which are characterized by relatively fixed or stable local conformations, and have apparent CT association constants closely resembling these of comparable model complexes. Other residues may be located in a region where the protein conformation is flexible or continuously mobile, as evidenced by their smaller apparent association constants. It is probably significant that Trp-62 of lysozyme and Trp-215 of trypsin, both specificity site residues, appear to belong to the class of residues which can be considered as being in a flexible environment on the protein surface.
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PMID:Charge-transfer studies of the availability of aromatic side chains of proteins in guanidine hydrochloride. 117 11

The binding of the beta-1-4-linked trimer of N-acetyl-D-glucosamine to hen egg-white lysozyme was studied by rapid-reaction-kinetic methods with tryptophyl fluorescence observation of the transients. It was found that discrete segments of the fluorescence-difference spectrum from this reaction were perturbed at different time-points during the binding process. The results were interpretated as the formation of the initial complex, the fast phase of the reaction, perturbing the environment of tryptophan-62 and a subsequent and slower rearrangement of the initial complex perturbing the environment of tryptophan-108. At pH 4.4, the release of protons from aspartate-101 occurred during the rearrangement step of the binding reaction. A model for the reaction is presented (E, enzyme; L, ligand): (see article) The association of this ligand with lysozyme may be visualized in three-dimensional terms as initial complex-formation across the top of the active-site cleft followed by a diving motion of the ligand into the cleft.
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PMID:Stopped-flow fluorescence studies on saccharide binding to lysozyme. 118 Sep 4

The previously described peptide 62-68 (Cys 64-Cys 80) 74-96 (Cys 76-Cys 94) (Atassi, M.Z., Suliman, A.M. and Habeeb, A.F.S.A. (1975) Biochim. Biophys. Acta 405, 452-463), which accounted for about one-third of the total antigenic reactivity of native lysozyme, was isolated here with lysine 97 attached to it. The peptide was subjected to specific modification reactions in order to determine some of the residues which formed part of its antigenic reactive site. ORD measurements showed that the peptide was greatly unfolded in solution relative to its expected mode of folding within the intact lysozyme molecule. Modification of the two tryptophan residues in the peptide by reaction with 2,3-dioxo-5-indolinesulfonic acid provided a derivative which possessed similar conformational parameters to those of the unmodified peptide. However, the derivative retained only about half the immunochemical reactivity of the peptide. Succinylation of the amino groups afforded a derivative whose conformational parameters were identical to those of the unmodified peptide but in which half of the immunochemical reactivity was lost. Modification of the two tryptophan residues followed by succinylation of the amino groups resulted in almost complete loss of the antigenic reactivity, and the loss was not due to conformational differences. The antigenic reactivity of the peptide was also destroyed on removal of tryptophans 62 and 63, of sequence 84-93 from the loop 74-79 and of sequence 74-75 by chymotryptic digestion. From these and previous results it was concluded that the antigenic reactive site in this part of the lysozyme molecule incorporates one or both of tryptophans 62 and 63 as well as one or both lysines 96 and 97. The two disulfides 64-80 and 76-94 bring these two parts of the lysozyme molecule into a single reactive site. The intactness of the disulfides is essential for maintenance and reactivity of the site.
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PMID:Enzymic and immunochemical properties of lysozyme. XI. Conformation and immunochemistry of the two-disulfide peptide and the tryptophan and lysine residues in its antigenic reactivity. 118 Sep 68

A tryptophan residue in hen's egg-white lysozyme [EC 3.2.1.17] was modified by ozone in an aqueous solution. One of the six tryptophan residues in the enzyme was oxidized to N'-formylkynurenine with concomitant loss of the enzymatic activity. Physicochemical studies of this modified enzyme (OL-I) revealed that the ozonization of lysozyme in aqueous media resulted in little change of the gross molecular conformation. It was deduced that the modified tryptophan residue in OL-I was possibly located in position 62 (or 63) of the protein.
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PMID:Oxidation of tryptophan in lysozyme by ozone in aqueous solution. 121 83

Upon preincubation with urea, various 3- or 4-substituted N-methylpyridinium salts form charge-transfer complexes with tryptophan containing proteins such as, L-chymotrypsin and lysozyme. The complexes were studied by using the difference spectrophotometric technique. The fluorescence examination showed that tryptophyl residues in protein molecules are engaged in the complex formation process. The complex formation reactions proceed at a considerable rate. The stopped-flow method was used to determine the pseudo first order rate constants. A linear dependence of the pseudo first order rate constants with the donor concentration was found. The second order rate constants were obtained by dividing the mean value of the pseudo first order rate constants by the initial donor concentration for each run. The linear dependence of second order rate constants with the electron affinity of the acceptors can serve as a criterion for the formation of charge-transfer complexes.
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PMID:The kinetics of complex formation of tryptophan containing proteins with pyridinium salts. 121 82

The rates of complex formation of free tryptophan and hen egg-white lysozyme with tetracyanoethylene have been investigated at different molar ratios. The reaction rates were studied by the "stopped-flow" method. The complex forming reactions follow a first order kinetics. A linear relationship of kobs. with donor concentration was found. This shows that the complex with a composition of 1:1 is predominant independently of the molar ratio between donor and acceptor. The rate of complex formation of free tryptophan and tetracyanoethylene was compared with the rate of complex formation between tetracyanoethylene and tryptophanyl residues in the lysozyme molecule. The kinetic data showed that the process of complex formation with tryptophanyl residues is slow.
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PMID:A kinetic study of complexes of tryptophan and lysozyme with tetracyanoethylene. 123 44

Under hydrolytic conditions using 6 M HCl, tryptophan reacted separately with dithiodiglycolic acid and cystine to give beta-3-oxindolylalanine (beta-[3-(2-indolinone)]alanine) as the main product. A compound, which eluted in the amino acid analyzer at the same position as beta-3-oxindolylalanine, was found in the acid hydrolyzate of lysozyme. The identicalness of these two compounds was established by comparison of their ultraviolet absorption spectra, elution positions on ion exchange chromatograms, etc. The "acid degradation product of tryptophan", which is known to be produced upon acid hydrolysis of tryptophan-containing proteins, must also be the same compound.
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PMID:Beta-3-Oxindolylalanine: The main intermediate in tryptophan degradation occurring in acid hydrolysis of protein. 125 56

Reaction of hen egg-white lysozyme with 2,3-dioxo-5-indolinesulfonic acid (DISA) yielded a homogeneous derivative which was modified at a single tryptophan residue. The modification was located at Trp-123. The absorption spectrum of the derivative showed a new peak in the visible range with lambdamax at 365 nm. In addition, the absorption maximum in the ultraviolet which appears in lysozyme at 280 nm was shifted to 270 nm in the derivative and appreciably enhanced. In ORD measurements, the rotatory behaviors of lysozyme and its derivative were identical at the 233 nm negative minimum and the 199 nm positive extremum. CD measurements gave equal [theta] values for lysozyme and derivative at the two negative ellipticity bands at 208 and 220 nm. Although no conformational differences between lysozyme and derivative were observed by ORD and CD measurements, some changes were detectable by chemical methods. Accessibility to tryptic hydrolysis and susceptibility of the disulfide bonds to reduction were increased in the derivative relative to lysozyme. The lytic activity of the derivative, which retained the same pH optimum as native lysozyme, was greatly (50%) decreased, probably as a result of the slight conformational change. With several antisera to lysozyme, the native protein and its derivative had equal antigenic reactivities. The findings were instrumental in further delineation of an antigenic reactive site in lysozyme.
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PMID:Conformation, enzymic activity, and immunochemistry of a lysozyme derivative modified at tryptophan 123 by reaction with 2,3-dioxo-5-indolinesulfonic acid. 125 90

Steady-state and transient fluorescence properties of turkey lysozyme, human lysozyme, and bovine alpha-lactalbumin are compared to those of hen lysozyme and hen lysozyme derivatives. Tryptophan fluorescence appears to be sufficiently sensitive to environment so that a small divergence in sequence can alter the fluorescence properties of one or more of the sequentially equivalent tryptophans in these proteins. Thus, an understanding of the fluorescence of one protein cannot necessarily be extended to a homologous protein in a simple manner, and the use of fluorescence to document structural similarity in homologous proteins is likely to be difficult. In addition, the results with alpha-lactalbumin and human lysozyme suggest that multiple conformations of these proteins exist in solution, and that interconversion of these conformations is slow compared to the fluorescence lifetime.
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PMID:Tryptophan fluorescence and homology in lysozymes and alpha-lactalbumins. 126 10


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