首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The isolation of lysozyme from the egg white of several representative species of waterfowl is described. The purified lysozymes were analyzed in order to determine the type and molecular weight of each enzyme. All enzymes found in duck egg whites were found to be of the c-type. In contrast all true geese, the Mute Swan as well as the Northern Blackneck Screamer contain lysozyme g in their egg white.  相似文献   

2.
Abstract Wild waterfowl species often nest in conditions where high humidity and microbial contamination may influence egg survival and quality. Albumen is traditionally regarded as the major impediment to microbial contamination of eggs, and its composition and activity may be selected by environmental pressures. Egg white protein from the eggs of wood duck (Aix sponsa), hooded merganser (Lophodytes cucullatus), Canada goose (Branta canadensis), and mute swan (Cygnus olor) was evaluated in order to compare the antimicrobial defenses of these species. Ovotransferrin and ovalbumin were identified in all species, but c-type lysozyme was present only in wood duck and hooded merganser egg white samples. Wood duck egg white showed the greatest bacterial activity as well as the highest lysozyme content. Egg white from wood duck and hooded merganser possessed greater lysozyme activity under acidic conditions, suggesting a c-type lysozyme with a pH optimum lower than that of Gallus gallus c-type lysozyme or the presence of g-type lysozyme. Ovotransferrin bacteriostatic activity appeared to be similar across the species investigated. The results suggest that lysozyme and ovotransferrin play a role in the antimicrobial defense of the avian egg. High levels of the broad-acting c-type lysozyme appear to have evolved in the albumen of the wood duck in order to ensure proper development of the embryo in the humid conditions of the cavity nest.  相似文献   

3.
4.
Polymorphism of serum and egg amylase by means of horizontal agarose gel electrophoresis and egg lysozyme by means of horizontal starch gel electrophoresis in Pekin, Muscovy ducks and their interspecific hybrids was studied. In the interspecific hybrids of ducks the codominant type of heredity of serum, egg yolk and egg white amylase isozymes, as well as egg white lysozyme, were found.  相似文献   

5.
Egg white proteins of three species of tortoises and turtle and of hen have been compared by electrophoretic and immunochemical methods. The proteins lacked similarity in electrophoresis, but tortoise and turtle egg white proteins which did not crossreact with those of the hen showed some cross-reaction among themselves. The occurrence of lysozyme as two allelic variants which were distinguishable in electrophoresis was noted only in the egg white of one of the species of tortoise, namely, Trionyx gangeticus Cuvier. Tortoise lysozyme which showed strong lytic activity toward cell walls of Micrococcus lysodeikticus did not exhibit any cross-reaction with hen lysoyzme. It was purified, crystallized, and found to be homogeneous in sodium dodecyl sulfatepolyacrylamide gel electrophoresis, immunochemical tests, and sedimentation. The physicochemical and enzymatic properties of tortoise lysozyme were found to be strikingly similar to those of hen lysozyme with minor differences which could be due to differences in their primary structure. Its average molecular weight of 15,400 was determined from sedimentation and diffusion coefficient values, Archibald experiment, and amino acid composition. The molecule appeared to undergo pH-dependent expansion at pH 2 and dimerization above pH 5.7. In enzymatic properties, tortoise lysozyme showed a specific activity of 29,000–31,000 units and gave a pH optimum at pH 7.5 and an apparent Ka value of 250 mg· liter?1. Like hen lysozyme, its activity showed strong ionic strength dependence, weak chitinase activity, susceptibility to inhibition by N-acetyl-glucosamine, and stability toward heat.  相似文献   

6.
Lysozyme naturally present in raw hen egg white was immobilized by cross-linking the egg white foam with glutaraldehyde. Inclusion of N-acetyl glucosamine, a competitive inhibitor of lysozyme, was found to enhance the yield of lysozyme activity by fivefold.  相似文献   

7.
Deamidation of lysozyme was observed during storage in a buffer solution and in egg white. The peak corresponding to native lysozyme from Bio-Rex 70 column chromatography was gradually decreased, while the peaks corresponding to deamidated lysozyme were increased during storage in 0.1 m carbonate buffer at pH 9.5. A similar change was observed during storage in egg white, but the change in egg white was larger than that in the buffer solution. A detailed analysis of the elution peaks from the Bio-Rex 70 column suggested that one to three residues of amide in lysozyme were mainly deamidated during storage in the buffer solution, and that more than three residues in lysozyme were deamidated during storage in egg white. There were significant differences in lysozyme activity between native and deamidated lysozyme, the activity being decreased in proportion to the degree of deamidation.  相似文献   

8.
Functionalized Fe(3)O(4) nanoparticles conjugated with polyethylene glycol (PEG) and carboxymethyl chitosan (CM-CTS) were developed and used as a novel magnetic absorbing carrier for the separation and purification of lysozyme from the aqueous solution and chicken egg white, respectively. The morphology of magnetic CM-CTS nanoparticles was observed by transmission electron microscope (TEM). It was found that the diameter of superparamagnetic carboxymethyl chitosan nanoparticles (Fe(3)O(4) (PEG+CM-CTS)) was about 15 nm, and could easily aggregate by a magnet when suspending in the aqueous solution. The adsorption capacity of lysozyme onto the superparamagnetic Fe(3)O(4) (PEG+CM-CTS) nanoparticles was determined by changing the medium pH, temperature, ionic strength and the concentration of lysozyme. The maximum adsorption loading reached 256.4 mg/g. Due to the small diameter, the adsorption equilibrium of lysozyme onto the nanoparticles reached very quickly within 20 min. The adsorption equilibrium of lysozyme onto the superparamagnetic nanoparticles fitted well with the Langmuir model. The nanoparticles were stable when subjected to six repeated adsorption-elution cycles. Separation and purification were monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The lysozyme was purified from chicken egg white in a single step had higher purity, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Considering that the superparamagnetic nanoparticles possess the advantages of high efficiency, cost-effectiveness and excellent binding of a larger amount of lysozyme and easier separation from the reaction system, thus this type of superparamagnetic nanoparticles would bring advantages to the conventional separation techniques of lysozyme from chicken egg white.  相似文献   

9.
During an investigation of the effect of basic and acidic proteins on the growth of thermophilic aerobic sporeformers, crystalline egg albumin was found to be strongly bactericidal. This finding was uncharacteristic of acidic proteins. The bactericidal fraction was heat sensitive and separated from the non-bactericidal albumin fraction during gel filtration on Sephadex G-75. Cells of Micrococcus lysodeikticus and Bacillus stearothermophilus were lysed rapidly by the bactericidal component, leading to its tentative identification as lysozyme. The bactericidal substance possessed an electrophoretic mobility on polyacrylamide gel containing sodium dodecyl sulfate identical to that of crystalline egg white lysozyme. Users of crystalline egg albumin are cautioned that commerical preparations may be contaminated with lysozyme. Destruction of the thermophilic aerobes by lysozyme should be considered when performing counts on egg products.  相似文献   

10.
We have investigated the specificity of six different lysozymes for peptidoglycan substrates obtained by extraction of a number of gram-negative bacteria and Micrococcus lysodeikticus with chloroform/Tris-HCl buffer (chloroform/buffer). The lysozymes included two that are commercially available (hen egg white lysozyme or HEWL, and mutanolysin from Streptomyces globisporus or M1L), and four that were chromatographically purified (bacteriophage lambda lysozyme or LaL, bacteriophage T4 lysozyme or T4L, goose egg white lysozyme or GEWL, and cauliflower lysozyme or CFL). HEWL was much more effective on M. lysodeikticus than on any of the gram-negative cell walls, while the opposite was found for LaL. Also the gram-negative cell walls showed remarkable differences in susceptibility to the different lysozymes, even for closely related species like Escherichia coli and Salmonella Typhimurium. These differences could not be due to the presence of lysozyme inhibitors such as Ivy from E. coli in the cell wall substrates because we showed that chloroform extraction effectively removed this inhibitor. Interestingly, we found strong inhibitory activity to HEWL in the chloroform/buffer extracts of Salmonella Typhimurium, and to LaL in the extracts of Pseudomonas aeruginosa, suggesting that other lysozyme inhibitors than Ivy exist and are probably widespread in gram-negative bacteria.  相似文献   

11.
In several insect species, serum lysozyme and antibacterial peptide concentration increases after injection of bacteria and other foreign substances. The purpose of this study was to characterize the specificity of this induction in the tobacco hornworm, Manduca sexta. By 48 h after injection of killed bacteria, lysozyme activity was approximately tenfold greater than in untreated insects. This maximal response was observed after injection of every bacterial species tested and after injection of purified cell walls of Micrococcus luteus. A variety of acellular particles, soluble molecules, and bacterial cell wall components were either poor lysozyme inducers or elicited no change in lysozyme concentration. The polysaccharide zymosan from yeast cell walls was a moderate lysozyme inducer. Peptidoglycan from M. luteus cell walls was found to induce lysozyme to a level as great or greater than whole cell walls. Small fragments of peptidoglycan generated by hen egg white lysozyme digestion were isolated, partially characterized, and shown to be good inducers of lysozyme as well as other antibacterial peptides. It appears that peptidoglycan provides a signal that initiates antibacterial responses in the insect.  相似文献   

12.
1. Camel milk lysozyme was purified using heparin-Sepharose 4B, Sephadex G-75 and hydroxyapatite chromatography. By this procedure lysozyme was separated from lactoferrin and a low molecular weight protein. 2. The lytic effect of camel milk lysozyme was assayed using Escherichia coli and Micrococcus lysodeikticus and its activity was compared with that of lysozyme from human milk and egg white. 3. The specific activity of camel milk lysozyme was found to be lower than that of lysozyme from human milk or from egg white. 4. Camel milk lactoferrin did not show a lytic effect on bacteria, while the low molecular weight protein showed lytic activity.  相似文献   

13.
The egg white of C. atratus contains two forms of lysozyme, a 'chick-type' which is similar to that found in the egg white of the domestic hen, and a 'goose-type' similar to that found in the egg white of the Embden goose. The molecular structure of the goose-type lysozyme has been determined at a resolution of a 2.8 A by X-ray crystallographic analysis. The structure consists of two domains linked by a long stretch of alpha-helix. In all, there are seven helical segments in the structure. While there is no amino acid sequence homology with either hen egg-white or bacteriophage T4 lysozymes, there are portions of the structure where the folding of the main chain is similar to that found in portions of either hen egg-white lysozyme or T4 lysozyme or both. In particular, there is a consistency of structure in the arrangement of acid groups in the catalytic site. G-o plots calculated for this structure and for the bacteriophage T4 lysozyme structure show that both have similar 'modules' of structure with boundaries occurring at structurally equivalent positions. Three of the common boundaries are equivalent structurally to three of the four module boundaries observed in G-o plots of hen egg-white lysozyme. The variation in the position of the remaining boundary may be related to differences in substrate binding.  相似文献   

14.
A novel, cost-effective method of lysozyme separation from hen egg white was studied. This method integrates aqueous two-phase partitioning in the system EO50PO50/phosphates with membrane separation processes. The experiments were carried out in a pilot-scale on crude hen egg white.Initially, by forming an aqueous two-phase system, lysozyme was selectively extracted to the upper, polymer-rich phase while the other egg white proteins partitioned to the lower, phosphate-rich phase. Then, in order to recover lysozyme, thermoseparation of polymer-rich phase was applied. A novel approach for the simultaneous thermoseparation of the polymer-rich phase as well as for the recovery of the lysozyme was proposed, using a cross-flow microfiltration. Additionally, recovery of proteins by ultrafiltration from lower, phosphate-rich phase was also investigated.Lysozyme could be obtained after the thermal phase separation by means of microfiltration at a total recovery over the extraction steps of 47.5 and the purification factor of 10.5. The specific activity of lysozyme preparations was 34 188 U/mg of protein. Using cross-flow membrane techniques, it was found that the recovery of the polymer by microfiltration from the top phase was 83.9.  相似文献   

15.
L-Arginine (L-Arg) has been widely used as an enhancer of protein renaturation. The mechanism behind its action is still not fully understood. Using hen egg white lysozyme as a model protein, we present data that clearly demonstrate the suppression of the aggregation of denatured protein by L-Arg. By chemical modification of free cysteines, a series of unfolded lysozyme species were obtained that served as models for unfolded and intermediate states during the process of oxidative refolding. An increased equilibrium solubility of unfolded species and intermediates in the presence of L-Arg seems to be its major mechanism of action.  相似文献   

16.
We have studied the refolding and thermal denaturation of hen egg white lysozyme in a wide range of pH values (from 1.5 to 9.4) using stopped-flow circular dichroism (CD) and differential scanning calorimetry (DSC). A linear correlation was found between the thermal denaturation temperature (T(m)) and the logarithm of the refolding rate of the slow folding phase of hen egg white lysozyme (lnk(2)).  相似文献   

17.
A method based on cold ethyl alcohol fractionation at different pH levels and ionic strengths and on gel filtration on a Sephadex G-200 column was used to concentrate and purify lysozyme from the culture supernatant fluid of Staphylococcus aureus strain 524. The final, nondialyzable product exhibited a 163-fold rise in specific activity over that of the starting material. Staphylococcal lysozyme is a glycosidase which splits N-acetylamino sugars from the susceptible substrate. Staphylococcal lysozyme was shown to be similar to egg white lysozyme in its optimal temperature for reaction, optimal pH, activation by NaCl and Ca(++) ions, inhibition by sodium citrate and ethylenediaminetetraacetate, and inactivation by Cu(++) ions and sodium dodecyl sulfate. It differs from the egg white lysozyme in its temperature susceptibility range (staphylococcal lysozyme is inactivated at 56 C). It acts on whole cells and cell walls of Micrococcus lysodeikticus, murein from S. aureus 524, and cell walls of S. epidermidis Zak. The last substrate was not susceptible to the action of egg white lysozyme in the test system used. The mechanism of action of staphylococcal lysozyme seems to be analogous to that of egg white lysozyme; however, the biological specificity of the two enzymes may be different.  相似文献   

18.
The enzymatic behaviour, amino acid composition and some physical properties of a new endo-N-acetylmuramidase (B-enzyme) of Bacillus subtilis YT–25 were determined and compared with hen’s egg white lysozyme. The molecular weight was estimated to be about 13000 by the sedimentation equilibrium method. The isoelectric point was pH 9.8. The amino acid composition indicates that the enzyme is rich in basic amino acids, especially lysin. Maximal activity on the lysis of cell walls of M. lysodeikticus occurred at pH 6.2. The enzyme was stable at pH 3.5 ~ 6.0. The specific activity for the lysis of cell walls of M. lysodeikticus was less than fourth part of that of hen’s egg white lysozyme. Digest of cell walls of M. lysodeikticus with B-enzyme consisted greater numbers of high molecular products than digest with egg white lysozyme. Substrate specificity of B-enzyme seemed to be different from that of egg white lysozyme.  相似文献   

19.
Chicken egg white lysozyme exhibits antimicrobial activity against both Gram-positive and Gram-negative bacteria. Fractionation of clostripain-digested lysozyme yielded a pentadecapeptide with antimicrobial activity but without muramidase activity. The peptide was isolated and its sequence found to be I-V-S-D-G-N-G-M-N-A-W-V-A-W-R (amino acids 98-112 of chicken egg white lysozyme). A synthesized peptide of identical sequence had the same bactericidal activity as the natural peptide. Replacement of Trp 108 with tyrosine significantly reduced the antibacterial capacity of the peptide. By replacement of Trp 111 with tyrosine the antibacterial activity was lost. Replacement of Asn 106 with the positively charged arginine strongly increased the antibacterial capacity of I-V-S-D-G-N-G-M-N-A-W-V-A-W-R. The peptide I-V-S-D-G-N-G-M consisting of the eight amino acids of the N-terminal side had no bactericidal properties, whereas the peptide N-A-W-V-A-W-R of the C-terminal side retained some bactericidal activity. Replacement of asparagine 106 by arginine (R-A-W-V-A-W-R) increased the bactericidal activity considerably. The D enantiomer of R-A-W-V-A-W-R was as active as the L form against five of the tested bacteria, but substantially less active against Serratia marcescens, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus lentus. For these bacterial species some stereospecific complementarity between receptor structures of the bacteria and the peptide can be assumed.  相似文献   

20.
On the basis of the molecular evolution of hen egg white, human, and turkey lysozymes, three replacements (Trp62 with Tyr, Asn37 with Gly, and Asp101 with Gly) were introduced into the active-site cleft of hen egg white lysozyme by site-directed mutagenesis. The replacement of Trp62 with Tyr led to enhanced bacteriolytic activity at pH 6.2 and a lower binding constant for chitotriose. The fluorescence spectral properties of this mutant hen egg white lysozyme were found to be similar to those of human lysozyme, which contains Tyr at position 62. The replacement of Asn37 with Gly had little effect on the enzymatic activity and binding constant for chitotriose. However, the combination of Asn37----Gly (N37G) replacement with Asp101----Gly (D101G) and Trp62----Tyr (W62Y) conversions enhanced bacteriolytic activity much more than each single mutation and restored hydrolytic activity toward glycol chitin. Consequently, the mutant lysozyme containing triple replacements (N37G, W62Y, and D101G) showed about 3-fold higher bacteriolytic activity than the wild-type hen lysozyme at pH 6.2, which is close to the optimum pH of the wild-type enzyme.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号