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)

Nostoc punctiforme is a filamentous cyanobacterium that is capable of dark heterotrophy and cellular differentiation into nitrogen-fixing heterocysts, motile hormogonia, or spore-like akinetes. The study of akinete differentiation at the molecular level has been limited by the asynchronous development and limited number of akinetes formed within a filament. A system in which to study the development and genetic regulation of akinetes was investigated using a zwf mutant lacking glucose-6-phosphate dehydrogenase, the initial enzyme of the oxidative pentose phosphate pathway. Upon dark incubation in the presence of fructose, the zwf(-) strain ceased growth and differentiated into akinete-like cells, whereas the wild-type strain exhibited heterotrophic growth. Dark-induced zwf akinetes exhibited periodic acid-Schiff staining characteristics identical to that observed for wild-type akinetes, and synchronous induction of akinetes occurred in treated cultures. Dark-induced zwf akinetes exhibited increased resistance to the environmental stresses of desiccation, cold, or treatment with lysozyme relative to vegetative cells of both strains. Transcription of the avaK akinete marker gene was strongly induced in developing zwf akinetes as shown by Northern blotting and green fluorescent protein transcriptional reporter fusions. ATP levels did not vary significantly between dark incubated strains, indicating that a signal other than energy level may trigger akinete formation. This phenotypic and genetic evidence showing near-synchronous induction of dark-induced zwf akinetes indicates that this system will provide a valuable tool for the molecular genetic study of akinete development in N. punctiforme.
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PMID:Characterization of a model system for the study of Nostoc punctiforme akinetes. 1590 99

The influence of succinylation on lysozyme is studied using circular dichroism, fluorescence spectroscopy, and differential scanning calorimetry. The spectroscopic data reveal that at room temperature the structures of succinylated lysozyme and native lysozyme are similar. However, the calorimetric results show that the thermal stability of succinylated lysozyme is lower than that of native lysozyme. For succinylated lysozyme, the denaturation temperature (Td) varies in the range of 325-333 K (52-60 degrees C) and the associated denaturation enthalpy (DeltadenH) varies between 225 and 410 kJ/mol. For lysozyme, Td is 342-349 K (69-76 degrees C) and DeltadenH is 440-500 kJ/mol. From these data, the change in the heat capacity (DeltadenCp) upon thermal denaturation is derived. For lysozyme, DeltadenCp is 7.5 kJ/mol/K, and for succinylated lysozyme, it is 16.7 kJ/mol/K. The value of DeltadenCp for lysozyme is comparable to previously reported values. The high value of DeltadenCp for succinylated lysozyme is explained in terms of an extended degree of unfolding of the secondary structure and exposure of the apolar parts of the succinyl groups. Furthermore, the Gibbs energy of denaturation, as a function of temperature, derived from the thermodynamic analysis of the calorimetric data, indicates a cold-denaturated state of succinylated lysozyme below 20 degrees C. However, because a denatured state at low temperatures could not be detected by CD or fluorescence measurements, the native state may be considered to be metastable at those conditions.
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PMID:Effects of succinylation on the structure and thermostability of lysozyme. 1599 36

COSY proton nuclear magnetic resonance was used to measure the exchange rates of amide protons of hen egg white lysozyme (HEWL) in the pressure-assisted cold-denatured state and in the heat-denatured state. After dissolving lysozyme in deuterium oxide buffer, labile protons exchange for deuterons in such a way that exposed protons are substituted rapidly, whereas "protected" protons within structured parts of the protein are substituted slowly. The exchange rates k obs were determined for HEWL under heat treatment (80 degrees C) and under high pressure conditions at low temperature (3.75 kbar, -13 degrees C). Moreover, the influence of co-solvents (sorbitol, urea) on the exchange rate was examined under pressure-assisted cold denaturation conditions, and the corresponding protection factors, P, were determined. The exchange kinetics upon heat treatment was found to be a two-step process with initial slow exchange followed by a fast one, showing residual protection in the slow-exchange state and P-factors in the random-coil-like range for the final temperature-denatured state. Addition of sorbitol (500 mM) led to an increase of P-factors for the pressure-assisted cold denatured state, but not for the heat-denatured state. The presence of 2 M urea resulted in a drastic decrease of the P-factors of the pressure-assisted cold denatured state. For both types of co-solvents, the effect they exert appears to be cooperative, i.e., no particular regions within the protein can be identified with significantly diverse changes of P-factors.
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PMID:Pressure-assisted cold denaturation of hen egg white lysozyme: the influence of co-solvents probed by hydrogen exchange nuclear magnetic resonance. 1608 58

The use of hydrogel beads for the crystallization of proteins is explored in this contribution. The dynamic behaviour of the internal precipitant, protein concentration and relative supersaturation in a gel bead upon submerging the bead in a precipitant solution is characterized theoretically using a transient diffusion model. Agarose and calcium alginate beads have been used for the crystallization of a low-molecular-weight (14.4 kDa, hen egg-white lysozyme) and a high-molecular-weight (636.0 kDa, alcohol oxidase) protein. Entrapment of the protein in the agarose-gel matrix was accomplished using two methods. In the first method, a protein solution is mixed with the agarose sol solution. Gel beads are produced by immersing drops of the protein-agarose sol mixture in a cold paraffin solution. In the second method (which was used to produce calcium alginate and agarose beads), empty gel beads are first produced and subsequently filled with protein by diffusion from a bulk solution into the bead. This latter method has the advantage that a supplementary purification step is introduced (for protein aggregates and large impurities) owing to the diffusion process in the gel matrix. Increasing the precipitant, gel concentration and protein loading resulted in a larger number of crystals of smaller size. Consequently, agarose as well as alginate gels act as nucleation promoters. The supersaturation in a gel bead can be dynamically controlled by changing the precipitant and/or the protein concentration in the bulk solution. Manipulation of the supersaturation allowed the nucleation rate to be varied and led to the production of large crystals which were homogeneously distributed in the gel bead.
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PMID:Protein crystallization in hydrogel beads. 1613 62

Infection of Escherichia coli cells by T4 phage at a multiplicity of infection (MOI) of 0.01 caused inhibition of cell lysis for up to 4 h. Such cells grown under aerobic condition were lysed by external stimuli such as cold shock, osmotic shock or addition of toxic substances, e.g., carbonyl cyanide m-chlorophenylhydrazone (CCCP). However, the effects of these external stimuli were reduced by transferring the cells to static incubation, by which dissolved oxygen was consumed by the cells within 10 min. The cells became insensitive to such external stimuli when the culture was deoxygenated with nitrogen gas. Following infection with a lysozyme amber mutant, eL1a, the cell membrane permeability was found to be increased either by cold shock or osmotic shock treatment of cells grown under aerobic conditions, but not in cells transferred to the static incubation. Oxygen limitation was suggested to enhance membrane stability in relation to cell lysis following the cold or osmotic shock treatment.
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PMID:Characterization of oxygen-dependent lysis of Escherichia coli cells infected by bacteriophage T4. 1623 51

The effects of whey protein isolate (WPI) films and coatings incorporating lysozyme (LZ) on the inhibition of Listeria monocytogenes both in and on microbial media, as well as on cold-smoked salmon, were studied. The antimicrobial effects of LZ were examined using various growth media by turbidity and plate counting tests. Disc-covering and disc-surface-spreading tests were also used to evaluate the effects of WPI films incorporating LZ. Smoked salmon was used as a model food to test the antimicrobial effects of WPI coatings incorporating LZ, both initially and during storage at 4 and 10 degrees C for 35 days. Tensile properties (elastic modulus, tensile strength, and percentage of elongation), oxygen permeability, and color (Hunter L, a, and b) of WPI films with and without LZ were also compared. LZ inhibited L. monocytogenes in broth and on agar media. The number of cells surviving after LZ treatments depended on the type of media. WPI films incorporating 204 mg of LZ per g of film (dry basis) inhibited the growth of a preparation of 4.4 log CFU/cm2 L. monocytogenes. WPI coatings prepared with 25 mg of LZ per g of coating solution initially inactivated more than 2.4, 4.5, and 3.0 log CFU/g of L. monocytogenes, total aerobes, and yeasts and molds in smoked salmon samples, respectively. The WPI coatings incorporating LZ efficiently retarded the growth of L. monocytogenes at both 4 and 10 degrees C. The anti-L. monocytogenes effect of LZ-WPI coating was more noticeable when the coating was applied before inoculation than when the coating was applied after inoculation. Significantly higher elastic modulus values and lower percentage of elongation and oxygen permeability values were measured with the WPI films incorporating LZ than with the plain WPI films.
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PMID:Listeria monocytogenes inhibition by whey protein films and coatings incorporating lysozyme. 1630 68

The addition of human milk components with intrinsic antimicrobial activity to livestock milk by genetic engineering has the potential to benefit milk safety and production as well as the health of the lactating animal. As a model for the dairy cow, we generated transgenic goats that expressed human lysozyme in their milk at 68% of the levels found in human milk. Milk from these transgenic animals had a bacteriostatic effect on both in vitro and in vivo growth of several microorganisms important to the dairy industry. In vitro, milk from transgenic animals was capable of slowing the growth of mastitis-causing strains of Escherichia coli (P < 0.02) and Staphylococcus aureus (P < 0.05) as well as the cold-spoilage organism Pseudomonas fragi (P < 0.02). The growth of an organism involved in cheese-making, Lactococcus lactis, was not affected by the presence of lysozyme in milk. The supplementation of control milk with purified lysozyme did not achieve the same inhibitory effect as milk from transgenic animals. In vivo, milk from transgenic animals supported less bacterial growth than control milk. This transgenic model demonstrates the possibilities offered by genetic engineering to enhance the antimicrobial nature of milk and the udder.
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PMID:Human lysozyme expressed in the mammary gland of transgenic dairy goats can inhibit the growth of bacteria that cause mastitis and the cold-spoilage of milk. 1719 20

Enzymatic activity is dependent on temperature, although some proteins have evolved to retain activity at low temperatures at the expense of stability. Cold adapted enzymes are present in a variety of organisms and there is ample interest in their structure-function relationships. Lysozyme (E.C. 3.2.1.17) is one of the most studied enzymes due to its antibacterial activity against Gram positive bacteria and is also a cold adapted protein. In this work the characterization of lysozyme from the insect Manduca sexta and its activity at low temperatures is presented. Both M. sexta lysozymes natural and recombinant showed a higher content of alpha-helix secondary structure compared to that of hen egg white lysozyme and a higher specific enzymatic activity in the range of 5-30 degrees C. These results together with measured thermodynamic activation parameters support the designation of M. sexta lysozyme as a cold adapted enzyme. Therefore, the insect recombinant lysozyme is feasible as a model for structure-function studies for cold-adapted proteins.
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PMID:The lysozyme from insect (Manduca sexta) is a cold-adapted enzyme. 1797 17

The aim of the present study was to evaluate the expression of the Mytilus galloprovincialis lysozyme gene in different in vivo stress situations, including injection of bacteria Vibrio splendidus LGP32, Vibrio anguillarum or Micrococcus lysodeikticus, as well as heat shock at 30 degrees C and cold stress at 5 degrees C. Injection of V. splendidus LGP32 resulted in: (i) a general down-regulation of lysozyme gene expression, as quantified by Q-PCR; (ii) reduction in the number of circulating hemocytes; (iii) decrease in the percentage of circulating hemocytes expressing lysozyme mRNA which was now restricted to only small cells, as observed by ISH; and (iv) accumulation of hemocytes expressing lysozyme in the muscle sinus where injection took place. Injection of V. anguillarum or M. lysodeikticus induced significant up-regulation of lysozyme gene expression, but only 2-3days post-injection, with no change in the total hemocyte counts but an increased percentage of hemocytes expressing lysozyme mRNA. Neither the control injection of PBS-NaCl nor temperature stress modified the lysozyme expression pattern. Consequently, the hemocyte population appears to be capable of discriminating between stress factors, and even between 2 Vibrio species.
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PMID:Lysozyme gene expression and hemocyte behaviour in the Mediterranean mussel, Mytilus galloprovincialis, after injection of various bacteria or temperature stresses. 1849 91

The Methanococcoides burtonii small heat shock protein (Mb-sHsp) is an alphaB-crystallin homolog that delivers protein stabilizing and protective functions to model enzymes, presumably reflecting its role as a molecular chaperone in vivo. Although the gene encoding Mb-shsp was cloned from a cold-adapted microorganism, the Mb-sHsp is an efficient protein chaperone at temperatures far above the optimum growth temperature of M. burtonii. We show that Mb-sHsp can prevent aggregation in E. coli cell free extracts at 60 degrees C for 4 h and can stabilize bovine liver glutamate dehydrogenase for 3 h at 50 degrees C. Surface plasmon resonance was used to determine the binding affinity of Mb-sHsp for denatured proteins. Mb-sHsp bound tightly to denatured lysozyme but not to the native form. When Mb-Cpn and Mg(2+)-ATP were added to the reaction, bound lysozyme was released from Mb-sHsp establishing that Mb-Cpn is able to off-load folding intermediates from Mb-sHsp. In addition, Mb-sHsp and Mb-Cpn also function cooperatively to protect an enzyme substrate. Through characterization of these M. burtonii chaperones, we were able to reconstitute a key heat shock regulated protein folding function of this cold adapted organism in vitro.
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PMID:Chaperone action of a versatile small heat shock protein from Methanococcoides burtonii, a cold adapted archaeon. 1895 10


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