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)

Spores of Bacillus megaterium ATCC 14581, subjected to partial-cell iradiation, were exposed to either lysozyme, H2O2, or glucose in an attempt to reduce or eliminate the nonmonotonic behavior in curves of percentage of germination versus energy, obtained when such spores were resuspended in phosphate buffer alone. Except at the lower doses. H2O2 effectively eliminated this anomalous dip in these curves, whereas lysozyme amplified it greatly. Glucose was generally ineffective. Coinciding with the increases in optical density when lysozyme was present was the formation of an occluding product.
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PMID:Effects of added germination agents on loss of optical density in electron-irradiated spores. 0 2

The antibacterial activity of a myeloperoxidase (MPO)-glucose oxidase system was found to be greatly increased by granulocyte elastase, present in azurophil granules of human neutrophils. The MPO-H2O3-mediated killing of both Escherichia coli and Staphylococcus aureus was potentiated by granuocyte elastase at an acid pH, whereas at pH 7.4 only killing of E. coli was potentiated. The potentiating effect of elastase was not dependent on the enzymatic properties of the protein since it was not abolished by heating, which destroys the enzymatic activity. A peptide chloromethyl ketone elastase inhibitor abolished both elastolytic activity and the pctentiating effects on MPO-H2-O2-mediated bacterial killing. The antibacterial activity of chymotrypsin-like cationic protein of human neutrophils was also potentiated by elastase. Other degradative enzymes isolated from human granulocytes, e.g., collagenase and lysozyme, did not potentiate MPO-H2O2-mediated or cationic protein-dependent bacterial killing. The present study indicates that a neutrophil constitutent, elastase, which is not microbicidal by itself, can initiate sublethal changes that render some microorganisms more susceptible to the action of microbicidal agents like MPO and chymotrypsin-like cationic protein.
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PMID:Microbicidal mechanisms of human granulocytes: synergistic effects of granulocyte elastase and myeloperoxidase or chymotrypsin-like cationic protein. 1 11

Conjugation of lysozyme with horse radish peroxidase by means of glutaraldehyde results in a complex which retains the activities of both enzymes. The incubation of peptidoglycan with lysozyme-peroxidase followed by the reaction with 3,3'-diaminobenzidine and H2O2 results in a strong labelling of both sides. In contrast, after treatment with peroxidase alone no reaction was observed. Thus, the specific binding of lysozyme-peroxidase can be used for the electron microscopic localization of this component in the bacterial cell wall. Isolated peptidoglycane as well as trypsinized cell walls of group A and C streptococci were labelled both on the inner and the outer surface. The surface of intact cells of group A- and C-streptococci was labelled only sparsely. In contrast, by means of the indirect immunoferritin technique strong labelling of intact cells was effected with specific anti-peptidoglycan antibodies. The specificity of these antibodies are mainly directed to the peptide side chains. From this we suggest that in the cell wall of group A and C streptococci the lysozyme-sensitive part of the peptidoglycan is not so superficially localized as the peptides.
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PMID:The use of lysozyme-peroxidase-conjugates for the electron microscopic detection of peptidoglycan in the cell wall of streptococci. 35 34

Microorganisms ingested by PMNs are exposed to a variety of antimicrobial systems. Together they comprise a formidable armamentarium, and few organisms survive. The predominant antimicrobial system would be expected to vary with the species, the availability of oxygen and the type of microorganism ingested. There is considerable evidence that the MPO-mediated antimicrobial system plays an important role in the destruction of certain microorganisms in most species; chicken heterophils, however, do not contain MPO,40 and some microorganisms are resistant to this system due to the nature of their cell wall material.146 Further, microbial catalase may offer some protection. The granulocytes of some species (e.g., rabbit, chicken) are rich in cationic proteins and these agents may play a particularly important role in these cells. Granular cationic proteins are less plentiful in human cells.111 Organisms vary in their susceptibility to lysozyme and this enzyme is absent from bovine leukocytes.113 It is probable that the total microbicidal potential of the leukocyte is in excess of its needs under most circumstances. This "overkill" capacity is a reflection of both the level of activity of individual systems and their variety. Particular organisms are susceptible to more than one antimicrobial system and thus may be effectively handled by back-up systems when one is absent. Thus, an organism normally killed by the peroxidase system may be handled less efficiently but adequately when MPO is absent by other oxygen-dependent antimicrobial systems. When a defect in oxidative metabolixm is present as in CGD, both MPO-catalyzed and nonenzymatic oxygen-dependent systems are absent. The ingested organism can, in some instances, supply the needed product of oxidative metabolism (i.e., H2O2); in other instances, oxygen-independent antimicrobial systems are adequate to prevent microbial growth. However, in yet other instances, the organisms survive and multiply and severe infection results.
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PMID:Antimicrobial mechanisms in neutrophilic polymorphonuclear leukocytes. 111 38

The site-specific lysozyme damage by iron and by iron-catalysed oxygen radicals was investigated. A solution of purified lysozyme was inactivated by Fe(II) at pH 7.4 in phosphate buffer, as tested on cleavage of Micrococcus lysodeikticus cells; this inactivation was time- and iron concentration-dependent and was associated with a loss of tryptophan fluorescence. In addition, it was reversible at pH 4, as demonstrated by lysozyme reactivation and by the intensity of the 14.4-kD-band on SDS-PAGE. Desferal (1 mM) and Detapac (1 mM) added before iron, prevented lysozyme inactivation, while catalase (100 micrograms/ml), superoxide dismutase (100 micrograms/ml) and bovine serum albumin (100 micrograms/ml) gave about 30 to 40% protection by competing with lysozyme for iron binding. The denaturing effect of iron on lysozyme was studied in the presence of H2O2 (1 mM) and ascorbate (1 mM); under these conditions the enzyme underwent partly irreversible inactivation and degradation different to that produced by gamma radiolysis-generated .OH. Catalase almost fully protected lysozyme; in contrast, mannitol (10 mM), benzoate (10 mM), and formate (10 mM) provided no protection because of their inability to access the site at which damaging species are generated. In this system, radical species were formed in a site-specific manner, and they reacted essentially with lysozyme at the site of their formation, causing inactivation and degradation differently than the hydroxyl radical.
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PMID:Mechanism of lysozyme inactivation and degradation by iron. 133 14

Ascorbic acid is believed to protect cells from oxidative damage by reacting with oxygen-derived free radicals. We investigated whether ascorbic acid would affect the rate of breakdown of skeletal muscle proteins in extracts exposed to hydrogen peroxide. Ascorbic acid (20 mmol/L) alone had little or no effect on the rate of ATP-independent or ATP-dependent breakdown of proteins in chicken skeletal muscle. Pretreatment of chicken skeletal muscle extracts with 10 mmol/L H2O2 resulted in a complete loss of ATP-dependent proteolysis and a significant increase (14- to 15-fold) in the rate of ATP-independent protein breakdown. Ascorbic acid (20 mmol/L) did not prevent H2O2 (10 mmol/L) from inactivating the ATP-dependent proteolytic pathway in skeletal muscle. However, ascorbic acid (20 mmol/L) prevented the H2O2-induced increase in the ATP-independent proteolysis of endogenous muscle proteins. Ascorbic acid also slowed the rate of hydrolysis of exogenously added [3H]superoxide dismutase exposed to H2O2 and inhibited the enhanced degradation of [3H]lysozyme and H2O2-treated [3H]superoxide dismutase by the proteolytic systems exposed to H2O2. Thus ascorbic acid seems to inhibit the H2O2-induced increase in ATP-independent proteolysis 1) by preventing damage to proteins by H2O2 resulting in a decreased supply of substrates for the ATP-independent degradative system and 2) by preventing activation of the proteolytic enzymes that participate in the energy-independent degradation of H2O2-treated proteins.
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PMID:Protective effect of ascorbic acid on the breakdown of proteins exposed to hydrogen peroxide in chicken skeletal muscle. 143 49

The reactions of hydroxyl radicals generated from FeII/H2O2 and CuII/H2O2 redox couples with a variety of proteins (BSA, histones, cytochrome c, lysozyme and protamine) have been investigated by e.s.r. spin trapping. The signals obtained, which are generally anisotropic in nature, characterize the formation of partially-immobilized spin-adducts resulting from attack of the HO. radicals on the protein and subsequent reaction of the protein-derived radicals with the spin trap. Similar spin adducts are observed on incubation of two haem-proteins (haemoglobin and myoglobin) with H2O2 in the absence of added metal ions implying a reaction at the haem centre followed by internal electron transfer reactions. Two strategies have been employed to obtain information about the site(s) of radical damage in these proteins. The first involves the use of a variety of spin traps and in particular DMPO: with this particular trap the broad spectra from largely immobilized radicals show characteristic a(beta-H) values which enable carbon-, oxygen- and sulphur-centred radicals to be distinguished. The second involves the use of enzymatic cleavage of first-formed adducts to release smaller nitroxides, with isotropic spectra, which allow the recognition of beta-proton splittings and hence information about the sites of radical damage to be obtained. These results, which allows backbone and side-chain attack to be distinguished, are in agreement with random attack of the HO. radical on the protein and are in accord with studies carried out on model peptides. In contrast the use of less reactive attacking radicals [N3., .CH(CH3)OH] and oxidising agents (Ce4+) provides evidence for selective attack on these proteins at particular residues.
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PMID:Radical-induced damage to proteins: e.s.r. spin-trapping studies. 166 98

Increased secretion of H2O2, O2- and lysozyme by human monocytes in vitro on treatment with cisplatin, rIFN-Y (interferon-Y), LPS (lipopolysaccharide) and MDP (muramyl dipeptide) is reported. It is suggested that increased production of these secretory products represent the activated state of monocytes. These in vitro activated monocytes could either kill the tumor cells via increased contact mediated cytolysis or cytolysis mediated via the release of the secretory products like H2O2, O2- and lysozyme.
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PMID:Effect of cisplatin, rIFN-Y, LPS and MDP on release of H2O2, O2- and lysozyme from human monocytes in vitro. 166 47

The effect of hydrogen peroxide (H2O2) was examined on baseline and on methacholine- and phenylephrine-stimulated smooth muscle tone, mucus volume and lysozyme outputs, and epithelial albumin transport of the ferret whole trachea in vitro. H2O2 (10 microM-10 mM) had no significant effect on tracheal smooth muscle tone but produced concentration-dependent increases in mucus volume, lysozyme and albumin outputs. The potential difference (P.D.) across the trachea was not changed by H2O2. Exposure of the trachea to H2O2 (1 mM) for 2 h reduced the smooth muscle contractions and lysozyme outputs due to methacholine (1 microM) and phenylephrine (10 microM). Methacholine-induced albumin output was significantly increased by H2O2 but that due to phenylephrine was not significantly affected. Exposure to H2O2 had no significant effect on the mucus volume output produced by methacholine or phenylephrine. Thus H2O2 directly stimulates submucosal gland secretion, including secretion from serous cells, and epithelial albumin transport across the ferret trachea but has no effect on tracheal smooth muscle tone. H2O2 reduces methacholine- and phenylephrine-induced smooth muscle contractions and serous cell secretion. H2O2 causes hyperresponsiveness of albumin output to methacholine but not to phenylephrine.
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PMID:The effect of hydrogen peroxide on smooth muscle tone, mucus secretion and epithelial albumin transport of the ferret trachea in vitro. 180 98

This study investigated the interaction between neutrophil myeloperoxidase (MPO) and the C1q component of the complement system. Using a dot-spot assay, MPO was found to bind to C1q in a dose-dependent manner. The specificity of this reaction was proved by the inhibitory effect of F(ab')2 antibodies to C1q and by the inability of MPO to bind to C1r, C1s and IgG. The interaction between MPO and C1q did not influence the enzymatic activity of the peroxidase but resulted in a more stable C1q as assessed by hemolytic assay for C1q. The protective effect of MPO on C1q did not require the presence of H2O2 in the reaction mixture nor was it inhibited by sodium azide, whereas it was abolished by heating the peroxidase. Lactoferrin and lysozyme, unlike MPO, were ineffective in protecting C1q from functional decay. Addition of H2O2 and chloride to MPO and C1q led to a complete inactivation of C1q, which could not be induced by H2O2 alone. The hypochlorite, which is known to be generated during the reaction of MPO with H2O2 and chloride, exhibited a similar inactivating effect on C1q, which was prevented by an external source of methionine.
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PMID:Protective and inactivating effects of neutrophil myeloperoxidase on C1q activity. 215 59


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