Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

In a detailed study it was shown that washed cell suspensions of K. pneumoniae reduced the organophosphorus pesticide fensulfothion to fensulfothion sulfide. Temperature and pH optima for this conversion plus sensitivity to sulfhydryl-reacting agents strongly suggested enzyme involvement. The reaction was also quite sensitive to molecular oxygen, only proceeding under conditions of low oxygen tension. Once formed, the fensulfothion sulfide was rapidly bound by living and heat-killed cells. A combination of lysozyme treatment and differential centrifugation showed 90% of the sulfide to be concentrated in the cell membrane fraction of exposed cells.
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PMID:Conversion of fensulfothion by Klebsiella pneumoniae to fensulfothion sulfide and its accumulation. 622 Jun 91

Alteration of the surface of human neutrophils with the nonpenetrating, protein-inactivating agent p-diazobenzenesulfonic acid (DASA) was found to prevent activation of the respiratory burst by some stimuli, but not others. Production of superoxide anion (O2-) stimulated by concanavalin A or the chemotactic peptide formyl-methionyl-leucyl-phenylalanine FMLP was inhibited by DASA pretreatment, whereas O2- production stimulated by phorbol myristate acetate (PMA), sodium fluoride. or the ionophore A23187 was not inhibited by DASA. Pretreatment with DASA inhibited oxygen uptake stimulated by FMLP, but not oxygen uptake stimulated by PMA. DASA reproducibly inhibited activities of two known surface enzymes Mg++-ATPase and alkaline phosphatase, by 45-55% and 60-70%, respectively. The inhibition by DASA of O2- production did not appear to be caused by interference with binding of the affected stimuli, since pretreatment with DASA did not inhibit release of the lysosomal enzymes lysozyme and myeloperoxidase induced by concanavalin A or FMLP. Membrane-rich particulate fractions from neutrophils have been shown to contain NADPH-dependent oxidative activity that is presumably responsible for the phagocytosis-associated respiratory burst of intact cells. The PMA-activated enzyme was susceptible to inhibition of directly exposed to DASA in this particulate fraction. These findings suggest that more than one mechanism exists for activation of the respiratory burst oxidase in human neutrophils, and that the neutrophil possesses at least one oxidase that is not an ectoenzyme.
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PMID:Respiratory burst enzyme in human neutrophils. Evidence for multiple mechanisms of activation. 625 8

Studies were performed to elucidate further the phenomenon of secretagogue-mediated enhancement in the binding of the chemoattractant f-met-leu-[3H]phe to human neutrophils (PMN). Specific f-met-leu-[3H]phe binding to unstimulated PMN reached maximum levels after 10 to 15 min of incubation at 0 degrees C with a saturating concentration of peptide, and consisted of a readily displaceable and a nondisplaceable component. PMN, preexposed to A23187 (2.5 X 10(-8) M) or PMA (0.5 ng/ml) for 30 min at 37 degrees C to stimulate limited and preferential release of specific (secondary) granules (10 to 20% of total lysozyme, no beta-glucuronidase), demonstrated an approximate doubling in the displaceable component of f-met-leu-["3H]phe binding, accompanied by an increasing nondisplaceable component that could not be explained by bulk pinocytosis of extracellular fluid (assessed by [3H]sucrose uptake). The increase in f-met-leu-[3H]phe binding was not affected by inhibitors of protein synthesis, could not be attributed to the secreted products lysosyme or lactoferrin acting on the cell, and, on the basis of studies with PMN from patients with chronic granulomatous disease, could not be attributed to the effects of reactive oxygen species generated in low concentration during stimulation. Functional studies on PMN indicated that preexposure to secretagogues at concentrations demonstrated to increase receptor availability also enhanced subsequent f-met-leu-phe-mediated superoxide and hydrogen peroxide generation. The present data demonstrate that secretagogues may activate PMN to enhance their subsequent responses in f-met-leu-phe-mediated processes, and, combined with previous reports, support the concept that specific granules provide a source of preformed membrane and receptor material that is translocated to the cell surface during the secretion associated with directed locomotion.
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PMID:Correlation of human neutrophil secretion, chemoattractant receptor mobilization, and enhanced functional capacity. 627 63

Monocyte and neutrophil function assessed as antibody-dependent cell-mediated cytotoxicity (ADCC) using IgG-sensitizing human erythrocytes as target cells was enhanced in patients with severe psoriasis when compared to healthy controls. We found significant correlation between increased monocyte ADCC and increased neutrophil ADCC, No differences in basal cAMP levels and cAMP responses during initiation of the ADCC reaction was observed between psoriatics and normals. Also degranulation determined as lysozyme release during ADCC was normal. In contrast, the increase in ADCC was significantly correlated to an enhanced hexose monophosphate shunt activation in the effector cells during the cytotoxic reaction. Activity of enzymes responsible for the respiratory burst was not altered in psoriasis since superoxide production after stimulation with phorbol myristate acetate was normal. Likewise, oxygen consumption and degranulation following phagocytosis of opsonized zymosan particles in neutrophils was found normal in psoriasis. Since monocytes showed increased binding of IgG-sensitized erythrocytes these data indicate that the enhanced monocyte and neutrophil ADCC is caused by an enhancement of the respiratory burst possibly induced by increased Fc receptor activity.
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PMID:On the mechanism of enhanced monocyte and neutrophil cytotoxicity in severe psoriasis. 628 40

Granule contents from rat polymorphonuclear neutrophils were prepared by extraction with 0.2 M acetate (pH 4), dialyzed against phosphate-buffered saline (pH 7), and tested for bactericidal activity. Bactericidal assays consisted of mixing rat granule extract with 1 x 10(3) to 3 x 10(3) bacterial cells per ml at 37 degrees C for 1 h in a medium suited for bacterial growth. The granule extract demonstrated a distinctive dose-dependent bactericidal activity against outer membrane lipopolysaccharide mutants of Salmonella typhimurium LT-2, independent of added hydrogen peroxide or other active oxygen derivatives. The rough bacterial mutants showed an ordered increase in sensitivity to the rat lysosomal extracts inversely related to the length of their lipopolysaccharide carbohydrate side chains. Fractionation of the rat polymorphonuclear neutrophil granule extract with Sephadex G-100 column chromatography revealed an elution profile containing three major areas (peaks) of protein. Polyacrylamide gel electrophoresis and examination of enzymatic activity showed that these peaks contained myeloperoxidase (peak A), neutral protease (peak B), and lysozyme (peak C) activities. Also observed in peak C were cationic protein species whose cathodal electrophoretic migration was faster than that for lysozyme. Only peak C exhibited a bactericidal activity against the rough mutants of S. typhimurium LT-2 similar to that obtained for the unfractionated granule extract, with susceptibility of the bacterial mutants increasing with a progressive loss of carbohydrate residues in the lipopolysaccharide of the cell wall. The bactericidal activity of the peak C protein fraction was dose dependent. Boiling the unfractionated granule extract or peak C for 30 min had little affect on their antimicrobial activity when reacted against a deep-rough lipopolysaccharide mutant. However, trypsin pretreatment of these fractions significantly reduced their antimicrobial activity for the same mutant chemotype.
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PMID:Bactericidal activity of granule contents from rat polymorphonuclear leukocytes. 629 56

The understanding of mechanisms whereby phagocytic cells destroy intracellular microorganisms has progressed considerably in recent years. The interaction of phagocytes with microbes starts with binding of the latter to the phagocyte. This binding can be mediated by opsonins on the microorganisms, which then interact with appropriate receptors on the phagocyte surface. Other types of receptors, such as lectins, may also be involved in this process. Following internalization, the microbe will be enclosed in a vesicle (the phagosome), whose membrane is derived from the plasma membrane of the phagocytic cell. The phagosome will then normally undergo fusion with primary or secondary lysosomes. Various mechanisms can then lead to intracellular killing; some depend on oxidative processes, whereas other are independent of the oxidative metabolism. The former involve the activation of membrane enzyme systems that lead to a stimulation of oxygen uptake (the "respiratory burst"), and its reduction to molecular species that are highly toxic for microorganisms. Differences appear to exist in this regard between alveolar macrophages and other phagocytes, in which the respiratory burst is of higher magnitude. Oxygen-independent microbicidal mechanisms are based on the production of acid, on the secretion of lysozyme, on iron-binding proteins, and on the synthesis of toxic cationic polypeptides. Both oxygen-dependent and independent mechanisms appear to be increased in activated macrophages. Certain microorganisms have evolved countermeasures which enable them to avoid being destroyed by phagocytes; these are well illustrated by studies of the interaction between macrophages and protozoan parasites. Parasites such as Toxoplasma gondii (as well as certain mycobacteria) are able to inhibit fusion of phagosomes with lysosomes, thus escaping from the potentially harmful action of lysosomal hydrolases. Other microorganisms are able to resist the effect of such enzymes, perhaps by secreting inhibitory substances. Other still avoid lysosomes by leaving the phagocytic vacuole, to reach the cytosolic matrix where their development is unhindered. Finally, some microbes have enzymes to detoxify oxygen metabolites formed during the respiratory burst. Intracellular death or survival will thus depend on a delicate balance between several factors, some of which appear to be under genetic control.
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PMID:[Mechanisms of intracellular microbicide]. 634 79

An in vitro assay for assessing degradative action of neutrophils on basement membrane has been developed. Basement membrane adhering to the base of microtitre wells can be reacted with neutrophils allowing monitoring of the release of cell components or of isotope from labelled membranes. Using either sheep or rat renal membranes labelled with [3H]propionate it was shown that either rabbit anti-sheep basement membrane antibody or rabbit anti-rat nephrotoxic serum promoted degradation of the membranes by neutrophils from rabbits. Studies with proteinase inhibitors showed that the degradation was a result of proteolytic action. Comparisons of the effects of serum or plasma with the effects of heat-inactivated serum or plasma showed that complement did not increase degradative activity but did increase the exocytosis of lysozyme by the cells. Hydroxyl radical was the principal oxygen-derived metabolite produced by the cells but free radical scavengers had no effect on the extent of degradation effected by the cells.
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PMID:Degradation of rat or sheep glomerular basement membrane by rabbit neutrophils in vitro. The roles of proteinases, complement and oxygen-derived radicals. 639 84

The release of histaminase, a diamine oxidase of the human neutrophil, is initiated by soluble secretagogues. Histaminase is simultaneously inactivated by the reactive oxygen intermediates generated by the respiratory burst. Thus, quantitative assessment of histaminase release relative to other granule markers is best achieved in the presence of superoxide dismutase and catalase. Human neutrophils activated with secretagogues preferential for the specific granule, such as calcium ionophore A23187 in a limited concentration, phorbol myristate acetate (PMA), formyl-methionyl-leucylphenylalanine (fMLP), and concanavalin A, release vitamin B12-binding protein, lysozyme, and histaminase but not beta glucuronidase. PMA activation in the presence of cytochalasin B augments the release of lysozyme and initiates the release of beta glucuronidase through recruitment of the azurophilic granule but has no incremental effect on the release of vitamin B12-binding protein and histaminase observed with PMA alone. Subcellular fractionation of resting neutrophils by sucrose density gradient centrifugation to separate specific granules from two classes of azurophilic granules selectively distributes vitamin B12-binding protein and histaminase to the specific granule fractions.
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PMID:Localization of histaminase to the specific granule of the human neutrophil. 643 Jul 92

Methanobacterium thermoautotrophicum when grown on ordinary culture medium has a tough cell wall which is lysozyme-resistant and difficult to disrupt by physical means. The cell wall, however, can be weakened by the addition of D-sorbitol to the growth medium and the organisms form protoplasts after lysozyme addition. This technique allowed the isolation of two types of intracellular small vesicles: (a) isolated by disruption of the total cell population (lysozyme-sensitive and lysozyme-resistant cells) by ultrafrequency sound and (b) isolated by osmotic lysis of protoplasts. For the first time, a small vesicle fraction isolated as in (a) was capable of synthesizing methane from CO2 and H2 without cytoplasm. There was, however, an absolute requirement for a small, heat-stable, oxygen-sensitive cofactor which was isolated from the cytoplasm. Methane synthesis with this vesicle fraction was inhibited by the detergent deoxycholate, and by the protonophores 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone. Mg2+-ATPase appeared to be located on the outer or cytoplasmic surface of the small vesicle fraction isolated as in (b). The results were consistent with a previously made suggestion [Sauer, Erfle & Mahadevan (1981) J. Biol. Chem. 256, 9843-9848] that the interior of the small intracellular vesicles becomes acid during methane synthesis.
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PMID:Methane synthesis by membrane vesicles and a cytoplasmic cofactor isolated from Methanobacterium thermoautotrophicum. 646 20

Neutrophils from the synovial fluid (SFN) of 10 patients with active rheumatoid arthritis (RA) were investigated to determine the generation of oxygen intermediates (OI) (O2-, H2O2, OH .), chemiluminescence, and lysosomal enzymes (lysozyme and beta-glucuronidase). Lymphocytes from healthy individuals were cocultured at 37 degrees C for 17 hr with SFN from the patients and the number of OKT4+, OKT8+, and OKT3+ cells and the response to mitogens were determined. A markedly increased OI and slightly elevated lysosomal enzyme levels were observed in SFN from patients. Coculture of lymphocytes with SFN resulted in a decreased number of OKT4+ and OKT8+ cells and a greatly reduced response to Con A and mildly diminished response to PHA, while OKT3+ cells were not affected. The simultaneous addition of superoxide dismutase and catalase restored the impairment of monoclonal antibody reaction and lymphocyte responsiveness almost to control levels. It is suggested that the disturbed immunoreactivity of synovial fluid lymphocytes from RA patients may be due to increased OI generated by stimulated neutrophils.
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PMID:Effect of stimulated neutrophils from the synovial fluid of patients with rheumatoid arthritis on lymphocytes--a possible role of increased oxygen radicals generated by the neutrophils. 660 65


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