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)

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

The possible role of tyrosine phosphorylation in the activation of granulocytic HL60 cells was examined using vanadate, a phosphotyrosine phosphatase inhibitor. Treatment of permeabilized cells with micromolar concentrations of vanadate resulted in a substantial accumulation of tyrosine-phosphorylated proteins, detected by immunoblotting. At comparable concentrations, vanadate was also found to elicit an NADPH-dependent burst of oxygen utilization. Actin assembly, studied using 7-nitrobenz-2-oxa-1,3-diazole (NBD)-phallacidin, was similarly stimulated by vanadate, though considerably higher concentrations were required to observe this effect. In contrast with these responses, the secretion of lysozyme was not stimulated by vanadate, nor did vanadate affect calcium-induced secretion. Therefore, accumulation of tyrosine-phosphorylated proteins is associated with stimulation of some, but not all, of the responses characteristic of granulocytic cell activation. This indicates that the effects of vanadate are selective and suggests divergence of the signalling pathways leading to the individual effectors.
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PMID:Activation of permeabilized HL60 cells by vanadate. Evidence for divergent signalling pathways. 169 41

Plasma membranes were isolated and separated from thylakoid membranes by discontinuous sucrose density gradient centrifugation of crude membranes prepared by French pressure cell extrusion of lysozyme-treated Anacystis nidulans. Two distinct populations of chlorophyll-free plasma membrane vesicles were obtained exhibiting buoyant densities of 1.087 and 1.100 g/cm3 as opposed to a uniform density of 1.192 g/cm3 for thylakoid membranes. Plasma and thylakoid membranes were characteristically different also with respect to fatty acid and protein composition, cytochrome oxidase activity, and pigment content as analyzed by spectrophotometry, spectrofluorimetry, and high performance liquid chromatography. Apart from carotenoids, chlorophyll a was the only major photosynthetic pigment detected in thylakoid membranes while plasma membranes contained virtually no chlorophyll a but (besides large amounts of carotenoids) protochlorophyllide a and chlorophyllide a as revealed by solvent partition (between n-hexane and acetone or methanol), room and low temperature fluorescence emission and excitation spectra, and analytical separation and identification by high performance liquid chromatography and comparison with authentic standards. The protochlorophyllide in the plasma membrane could be transformed into chlorophyllide in the dark in vitro by incubating the membrane preparation with NADPH; NADP+ effected the reverse transition.
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PMID:Chlorophyll precursors in the plasma membrane of a cyanobacterium, Anacystis nidulans. Characterization of protochlorophyllide and chlorophyllide by spectrophotometry, spectrofluorimetry, solvent partition, and high performance liquid chromatography. 250 Dec 98

The assignment of cytochrome b-558 as a component of the O2- (H2O2) -generating enzyme in guinea-pig alveolar macrophages was investigated. Guinea pig alveolar macrophages contained 76 pmol cytochrome b-558/mg protein, a value very similar to that of neutrophils. The rate of myristic acid-stimulated O2- generation by alveolar macrophages, calculated per cytochrome b-558, was only one-fourth that of neutrophils. An analysis of Percoll density gradient centrifugation profiles showed that the H2O2-generating activity of myristic acid-activated alveolar macrophages was concentrated in a single peak which was consistently associated with 5'-nucleotidase activity, a plasma membrane marker enzyme. A little H2O2-generating activity was seen with unactivated alveolar macrophages. Furthermore, the cytochrome b-558 of both myristic acid-activated and unactivated alveolar macrophages was also predominantly associated with 5'-nucleotidase activity and was found in trace amounts in a peak containing lysozyme activity, a marker of lysosome granules. Only about 6% of the cytochrome b-558 in plasma membranes from myristic acid-activated guinea-pig alveolar macrophages was anaerobically reduced by 0.5 mM NADPH, while under the same conditions about 30% of the heme protein of myristic acid-activated neutrophils was reduced. These results suggest two conclusions: firstly, that in both activated and unactivated alveolar macrophages, cytochrome b-558 is located in the plasma membrane, and the translocation of cytochrome b-558 does not occur during the activation of NADPH oxidase; and secondly, that a smaller part of cytochrome b-558 is associated with the activated NADPH oxidase of guinea pig alveolar macrophages compared with neutrophils.
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PMID:Presence of cytochrome b-558 in guinea-pig alveolar macrophages-subcellular localization and relationship with NADPH oxidase. 283 23

The reducing equivalents used by the human neutrophil respiratory burst oxidase are derived from NADPH generated by the hexose monophosphate shunt. The CO2 generated by the HMP shunt is spontaneously hydrated and the protons (H+) are secreted upon the dissociation of carbonic acid. The mechanism and significance of H+ secretion by the resting and stimulated neutrophil was investigated. A basal rate of H+ secretion by resting neutrophils observed in a choline buffer was augmented with the addition of sodium (Na+) (Km for Na+ was 3.22 +/- 0.32 mM). Amiloride, a Na+/H+ antiporter inhibitor, reduced H+ secretion in Na+-containing buffers with a Ki = 1.02 microM. This Na+/H+ exchange mechanism was also operative in cells stimulated with a variety of agonists, and an increased H+ flux, relative to resting cells, was observed at higher Na+ concentrations. Cytoplasts incorporating acridine orange were also used to assess Na+-H+ flux. Cytoplasts were used to avoid alteration of the fluorescent pH probe by HOCl formed in intact neutrophils. Alkalinization of the cytoplasm was dependent on extracellular Na+ in concentrations similar to that found to augment H+ secretion in intact cells. Also, amiloride competitively inhibited H+ secretion by the cytoplasts. Both superoxide (O2-) production and lysozyme release in cells stimulated with opsonized zymosan or concanavalin A was significantly inhibited in the absence of Na+, restored to normal with the addition of Na+ in low concentrations, and inhibited again in the presence of amiloride. A Na+/H+ antiporter similar to that found in other cell types is present in the human neutrophil and appears linked to activation of the respiratory burst and degranulation.
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PMID:Proton secretion by the sodium/hydrogen ion antiporter in the human neutrophil. 300 66

Human colostral macrophages stimulated by opsonized zymosan or phorbol myristate acetate (PMA) released superoxide anions (O2-) and hydrogen peroxide (H2O2) with activities comparable to those of monocytes and about one-fourth of those of polymorphonuclear leukocytes (PMNL) of blood. The O2- -forming oxidase in the macrophages stimulated by PMA was dependent on NADPH as an electron donor with an apparent Km value for NADPH of 27.6 +/- 4.0 microM, which is comparable to those obtained for the stimulated monocytes and PMNL of blood. The Vmax was 1.86 +/- 0.33 nmol O2/min/10(6) cells, which is essentially the same as that of monocytes and about half of that of PMNL. p-Chloromercuribenzoate or cetyltrimethylammonium bromide completely inhibited oxidases of all three types of phagocytes. A b-type cytochrome was identified in the macrophages but the concentrations in the macrophages and monocytes were less than half of that in PMNL. These results suggest that the differences in the O2- -forming activities of the three types of phagocytes are quantitative rather than qualitative. The macrophages and monocytes showed very low activities of myeloperoxidase [EC 1.11.1.7] in contrast to PMNL. The activity of beta-glucuronidase [EC 3.2.1.31] in the macrophages was much higher than those of the monocytes and PMNL, but little difference was observed in the activities of lysozyme [EC 3.2.1.17], catalase [EC 1.11.1.6] and superoxide dismutase [EC 1.15.1.1] among the three types of phagocytes examined. Electron micrographs of the macrophages showed little increase of vacuoles upon exposure to PMA, in contrast to the cases of monocytes and PMNL.
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PMID:Oxygen metabolism of human colostral macrophages: comparison with monocytes and polymorphonuclear leukocytes. 608

The effect of modification of maleimide derivatives on superoxide production by guinea-pig neutrophils induced by a variety of different soluble stimuli was studied. Pretreatment of neutrophils by showdomycin, a very slowly penetrating-SH reagent, did not affect superoxide production by all of the stimuli used, suggesting no exposure of sulfhydryl groups involved in superoxide-generating system on the cell surface. Pretreatment with N-ethylmaleimide (MalNEt), a considerably penetrating-SH reagent, markedly inhibited superoxide production stimulated by formyl-methionyl-leucyl-phenylalanine (HCO-Met-Leu-Phe), cytochalasin E or digitonin, but not superoxide production stimulated by the ionophore A23187 or sodium fluoride. The oxygen consumption stimulated by HCO-Met-Leu-Phe or cytochalasin E was inhibited by MalNEt pretreatment, whereas the oxygen consumption stimulated by A23187 was not inhibited by MalNEt. The inhibition by MalNEt of superoxide production did not appear to be due to the interference with binding of the affected stimuli, since MalNEt pretreatment did not inhibit the release of lysozyme, granule enzyme, induced by HCO-Met-Leu-Phe, cytochalasin E or digitonin. Particulate fractions from MalNEt-pretreated neutrophils before exposure to the stimulus exhibited the inhibition of the enhancement of NADPH-dependent superoxide production induced by HCO-Met-Leu-Phe, cytochalasin E or digitonin, but not A23187, whereas treatment of neutrophils with MalNEt after activation by these stimuli had no effect on the NADPH oxidase activity in particulate fractions. Direct exposure of particulate fractions from A23187-stimulated neutrophils to MalNEt showed no actual susceptibility of NADPH oxidase to MalNEt inhibition. These findings suggest that the inhibitory effect of MalNEt is caused by the modification of the process of the activation by the affected stimuli of the superoxide system, probably NADPH oxidase and that at least two mechanisms exist for activation of superoxide-generating system in guinea-pig neutrophils on the basis of the susceptibility to MalNEt inhibition.
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PMID:Effect of maleimide derivatives on superoxide-generating system of guinea-pig neutrophils stimulated by different soluble stimuli. 609 85

In order to resolve discrepancies in the literature concerning the subcellular localization of NADPH oxidase, we disrupted human neutrophils by nitrogen cavitation and fractionated the subcellular organelles on a discontinuous sucrose density gradient. The lightest fraction was 20- to 40-fold enriched for plasma membranes as determined by the marker enzymes alkaline phosphatase and phosphodiesterase I as well as by the ratio of lipid phosphorus to protein. There was a significant decrease in the specific activities of the granule markers myeloperoxidase, lysozyme, and beta-glucuronidase. An intermediate fraction was enriched in membrane markers but not to the extent the lightest fraction was enriched. This fraction contained more granular contamination, as shown by the marker enzymes. In contrast, the densest bands of the gradient were enriched for granule markers with little contamination by plasma membrane. Superoxide generation and NADP formation were primarily associated with the two membrane-enriched fractions from polymorphonuclear leukocytes stimulated with phorbol myristate acetate. The NADP formation associated with a dense granule fraction observed previously in our laboratory was probably due to a cyanide-stimulated oxidation of NADPH by myeloperoxidase.
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PMID:Co-localization of superoxide generation and NADP formation in plasma membrane fractions from human neutrophils. 609 76

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

Biliverdin reductase in a stable form was purified to homogeneity from rat liver cytosol. The purified enzyme showed 3700-fold increase in specific activity when compared with the crude preparation, and the extent of recovery was 30-35%. The molecular weight was estimated at 34,000-36,000. The amino acid analysis of the purified preparation revealed the presence of 3 cysteine residues/mol of enzyme. The reductase utilized NADPH and NADH as electron donors. The NADPH-dependent biliverdin reductase activity was extremely sensitive to SH reagents, including 5,5'-dithiobis(2-nitrobenzoic acid), N-ethylmaleimide, p-chloromercuribenzoic acid, and iodoacetamide. However, the pretreatment of the enzyme with NADPH and biliverdin fully protected the reductase from inactivation by these reagents. The enzyme activity was irreversibly inhibited by HgCl2. The addition of dithiothreitol to the enzyme inhibited by 5,5'-dithiobis(2-nitrobenzoic acid) promoted the full reversal of inhibition. The enzyme exhibited different pH optima for activity with NADPH (pH 8.7) and NADH (pH 7.0). The apparent Km for biliverdin was established to be 5.0 microM with NADH and 3.0 microM with NADPH. The apparent Km for NADPH was 3.0 microM, while that of NADH was 270 microM. The enzyme activity was inhibited by the substrate when the concentration exceeded 4.0-5.0 microM. The product, bilirubin, inhibited the enzyme activity in a competitive manner. In addition, the reductase was inhibited by hematin and zinc-protoporphyrin. Dilution produced instability in the enzyme, but the presence of exogenous proteins, such as serum albumin, beta-lactoglobulin, and lysozyme, stabilized the enzyme protein.
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PMID:Purification and characterization of biliverdin reductase from rat liver. 721 67


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