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 kinetics of the photodynamic desactivation of lysozyme in presence of acridine orange as the sensitizer have been investigated in detail varying oxygen, protein, dye concentration, ionic strength and pH value. The kinetics can be approximately described as an over all pseudo-first-order rate process. Changing the solvent from water to D2O or by quenching experiments in presence of azide ions it could be shown that the desactivation of lysozyme is caused exclusively by singlet oxygen. The excited oxygen occurs via the triplet state of the dye with a rate constant considerably lower than that to be expected for a diffusionally controlled reaction. Singlet oxygen react chemically (desactivation, k=2.9 X 10(7) m(-1) sec(-1)) and physically (quenching process, k=4.1 X 10(8) m(-1) sec(-1)) with the enzyme. The kinetical analysis shows that additional chemical reaction between singlet oxygen and lysozyme would have only little influence on the kinetics of the desactivation as long as their products would be enzymatically active and their kinetical constants would be less than about 1 X 10(8) m(-1) sec(-1)).
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PMID:On the mechanism of the acridine orange sensitized photodynamic inactivation of lysozyme. I. Basic kinetics. 0 28

Incorporation of L-[14C]ornithine into gramicidin S by crude, unfractionated lysozyme extracts of Bacillus brevis ATCC 9999 was shown to represent the activity of the gramicidin synthetase complex. Frozen-thawed cells were the source of active extracts, but when cells were shaken in air at 37 degrees C, they rapidly lost activity in a first-order reaction with a half-life of 13 min. Protease inhibitors and inhibitors of energy metabolism had no effect on the inactivation process in frozen-thawed cells. Stabilization was achieved when the cells were shaken in nitrogen or helium instead of air. The addition of dithiothreitol produced a moderate degree of stabilization. The L-ornithine- and D-phenylalanine-activating activities of the gramicidin S synthetase complex were also lost during aeration of the cells. Crude cell-free extracts also lost activity when they were shaken in oxygen, but, in this case, inactivation was slower (half-life of 80 min). Nitrogen also stabilized these cell-free extracts.
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PMID:Oxygen-dependent inactivation of gramicidin S synthetase in Bacillus brevis. 6 33

The photodynamic deactivation of lysozyme in presence of acridine orange is caused by a reaction between singlet oxygen formed via the dye triplet state and the protein. In order to identify the region where the singlet oxygen reacts with the protein we have investigated the kinetics of the deactivation in presence ofthe inhibitor of the enzymatic reaction N-acetylglucosamine (GlcNAc). The overall experimental rate constant becomes slower with increasing saccharide concentrations. As we can exclude experimentally that this kinetical effect is caused in presence of the saccharide by a physical quenching of singlet oxygen or of the dye triplet state it has to be assumed that GlcNAc protects the surrounding of its bindings place at subsite C of the enzymatic center sterically against an attack of singlet oxygen. In this region three tryptophan residues are located, which could be sensitive against singlet oxygen. Surprisingly, however, it has been found that only those species are protected, in which a second saccharide molecule is bound to the protein, probably at subsite E at the enzymatic center, where no sensitive amino acid side chains are located.
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PMID:On the mechanism of the acridine orange sensitized photodynamic inactivation of lysozyme. II. Kinetics in presence of N-acetylglucosamine. 13 86

1. Cells of the hydrogen bacterium Alcaligenes eutrophus are broken by gentle lysis using lysozyme treatment in hypertonic sucrose followed by osmotic shock. By this method, 93% of the in vivo activity of the H2 oxidase is recovered and the ATPase remains particle bound. In contrast, cell disruption in a French pressure cell diminishes the in vivo activity of the H2 oxidase by 50% and solubilizes the bulk of the ATPase. 2. The bacterium contains a periplasmic cytochrome c with bands at 418, 521 and 550 nm (difference spectrum). In addition to cytochrome aa3, b-560, c-553 and o, low temperature difference spectra of membranes show the presence of two further cytochromes (shoulders at 551 and 553 nm). 3. The unsupplemented membrane fraction catalyses the oxidation of hydrogen, NADH, NADPH, succinate, formate and endogenous substrate (NAD linked) at rates 2--3-fold higher than membranes obtained from cells disrupted in a French pressure cell. With the exception of the H2 oxidase all oxidase activities in lysozyme membranes are sensitive to carbonylcyanide m-chlorophenylhydrazone (20-100% stimulation of oxygen uptake). 4. The cytoplasmic fraction contains a B-type cytochrome with absorption maxima at 436 and 560 nm, capable of combining with CO; it contains non-covalently bound protohaem. In alkaline solutions a spectral transition to the haemochrome type with bands at 423, 526 and 556 nm occurs. The addition of NADH to an aerobic suspension of this cytochrome elicits new absorption maxima at 418, 545 and 577 nm (difference spectrum), which are believed to represent an oxygenated form of the reduced cytochrome.
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PMID:Respiratory components and oxidase activities in Alcaligenes eutrophus. 18 46

Eight tests investigating the function of circulating polymorphonuclear leukocytes were performed in 68 subjects, half of whom smoked at least 20 cigarettes per day. Comparison of the two groups allowed determination of the in vivo effect of tobacco smoke on the nonspecific defense system of the body. Ingestion ability, oxygen consumption, and bactericidal activity were normal in smokers. Myeloperoxidase and neutrophil alkaline phosphatase activities also were unchanged. The nitroblue tetrazolium reduction and the serum lysozyme levels were slightly increased in smokers. The capillary tube random migration, though, was depressed, and intensive smoking further aggravated this change. It is suggested that tobacco smoke acts directly on one (or several) unidentified target site of polymorphonuclear leukocytes. This impairment, demonstrated in vivo, probably plays a role in the genesis of the bronchopulmonary diseases so frequent in heavy smokers.
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PMID:Effect of tobacco smoking on the functions of polymorphonuclear leukocytes. 22 75

The binding sites of Mn2+, Co2+, and Gd3+ have been determined in triclinic lysozyme at pH 4.5 to 4.6. Mn2+ and Co2+ bind a site approximately 2.5 A from 1 of the oxygen atoms of the Glu-35 chain. The occupancy of the Mn2+ site is 0.22, corresponding to 1 bound ion for each 4.6 protein molecules. The occupancy of the Co2+ site is much lower, about 0.048. Gd3+ appears to be bound at two sites, the main one 2.5 A from an oxygen atom of the Glu-35 side chain, the other 3.1 A from an oxygen atom of the Asp-52 chain. The occupancy of both Gd3+ sites is low, 0.036 and 0.016, the latter being so low that the presence of the ion at this site is in doubt. The binding site of Mn2+ in the di(N-acetylglucosamine)-lysozyme complex has also been determined. It does not differ significantly from the Mn2+ binding site in the native protein, but the occupancy is lower, 0.16.
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PMID:Metal ion binding in triclinic lysozyme. 24 Aug 35

Mechanisms were studied that might explain the attachment and damage to Candida albicans pseudohyphae by neutrophils in the absence of serum. Attachment of neutrophils to pseudo hyphae was inhibited by Candida mannans (1-10 mg/ml), but not by mannose, dextran, chitin, conconavalin A, or highly charged polyamino acids. Contact was also inhibited by pretreatment of Candida before incubation with neutrophils with chymotrypsin, but not trypsin or several inhibitors of proteases. Similar results were obtained with pretreatment of neutrophils, except that trypsin was inhibitory. When pseudohyphae were killed with ultraviolet light, proteinpolysaccharide complexes of mol wt <10,000 were released which appeared to bind to the surfaces of neutrophils and inhibit contact between neutrophils and Candida, as well as other fungi. Damage to Candida by neutrophils was inhibited by agents known to act on neutrophil oxidative microbicidal mechanisms, including sodium cyanide, sodium azide, catalase, superoxide dismutase, and 1, 4 diazobicyclo (2, 2, 2) octane, a singlet oxygen quencher. Neutrophils from a patient with chronic granulomatous disease did not damage Candida at all. However, the hydroxyl radical scavengers mannitol and benzoate were not inhibitory. Cationic proteins and lactoferrin also did not appear to play a major role in this system. Low concentrations of lysozyme which did not damage Candida in isotonic buffer solutions damaged pseudohyphae in distilled water. Isolated neutrophil granules damaged pseudohyphae only with added hydrogen peroxide and halide, and damage occurred only with granule fractions known to contain myeloperoxidase. These findings suggest that neutrophils recognized a molecule on the Candida surface which has a chymotrypsin sensitive protein component, and which may be liberated from the cell surface upon death of organism. The neutrophil receptors for Candida appear to be sensitive to trypsin and chymotrypsin. Damage to Candida by neutrophils occurred primarily by oxidative mechanisms, including the production of superoxide and hydrogen peroxide interacting with myeloperoxidase and halide, as well as singlet oxygen, but did not appear to involve hydroxyl radical. Lysozyme might have an accessory role, under some conditions.
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PMID:Mechanisms of attachment of neutrophils to Candida albicans pseudohyphae in the absence of serum, and of subsequent damage to pseudohyphae by microbicidal processes of neutrophils in vitro. 34 Apr 71

The hairy-cells (HC) of 10 patients with hairy-cell leukaemia were studied with several techniques to evaluate their phagocytic potential. Mononuclear cells from normal donors and from patients with acute monocytic leukaemia served as controls. Light microscopically HC seemed to have ingested bacteria or latex particles. Treatment of the cells with lysostaphin, an enzyme that kills extracellular Staphylococcus aureus, showed that almost all 'ingested' bacteria were extracellular. Lanthanum nitrate, added during the fixation procedure for electron microscopy, stained both the outer cell membrane and the membranes of the 'phagosomes' of the HC, also indicating that the 'ingested' particles were extracellular. HC showed no increased oxygen consumption on exposure to bacteria in the presence of serum. Furthermore, HC showed no lysozyme or peroxidase activity, whereas non-specific esterase activity was much weaker than in monocytes. These findings, which show that HC are essentially non-phagocytic, constitute strong evidence against a monocytic origin of the malignant cells of hairy-cell leukaemia.
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PMID:Phagocytic potential of hairy cells. 49 73

The photodynamic inactivation of lysozyme in air saturated H2O and D2O (phosphate buffer 0.05 M, pH 7.0) in the presence of methylene blue and riboflavin has been studied. When H2O was replaced by D2O a great increase in the rate of photoinactivation of lysozyme was observed. This finding, together with the fact that photooxidation is inhibited by singlet oxygen quenchers like NaN3, suggests that these reactions occur via a singlet oxygen mechanism. During the course of the studies of the riboflavin sensitized photoinactivation of lysozyme, it was found that riboflavin is strongly bound to the enzyme as a result of illumination. This finding would explain the higher quantum yield observed when riboflavin is used, although this dye is bleached during irradiation.
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PMID:Light-induced binding of riboflavin to lysozyme. 59 15

The effect of light was studied with the spheroplasts of the blue-green alga Anabaena variabilis. Contrary to the intact cells, the spheroplasts did not synthesize nucleic acids and pigments in the light. These components of the spheroplasts were decomposed in the light, and the remaining chlorophyll was incapable of luminescence. The rate of oxygen uptake increased upon the incubation of the spheroplasts in the light. Changes of the functions induced by lysozyme in the cells of A. variabilis are irreversible, contrary to those which are caused by the incubation in the darkness and can be restored if the cells are transferred into the light.
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PMID:[Comparative study of the functions of the spheroplasts and cells of the blue-green alga Anabaena variabilis]. 80 91


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