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)

Protein I, the major outer membrane protein of Neisseria gonorrhoeae, is a voltage-dependent anion channel which can translocate from the gonococcus into human cells. Since granule exocytosis from neutrophils is regulated by ion fluxes, we examined the effect of protein I on neutrophil activation. Pretreatment with protein I (250 nM) impaired degranulation from neutrophils: beta-glucuronidase release decreased to 27 +/- 6% S.E. of cells treated with N-f-Met-Leu-Phe (fMLP, 0.1 microM) and to 13 +/- 4% of cells treated with leukotriene B4 (LTB4, 0.1 microM); lysozyme release decreased to 52 +/- 17% of fMLP-treated cells and 22 +/- 9% of LTB4-treated cells. Morphometric analysis was consistent: control neutrophils increased their surface membrane after fMLP (43.3 +/- 5.6 microns relative perimeter versus 71.4 +/- 3.7 microns) while protein I-treated neutrophils did not (29.4 +/- 2 (S.E.) microns relative perimeter versus 34 +/- 4 microns). Enzyme release after exposure to phorbol myristate acetate was not affected (lysozyme: 86 +/- 27% of control). Cell/cell aggregation in response to fMLP was inhibited by treatment with protein I. However, generation of O2 was not affected. Protein I altered the surface membrane potential (Oxonol V): protein I evoked a transient membrane hyperpolarization which was not inhibited by furosemide. After exposure to fMLP, protein I-treated neutrophils underwent a furosemide-sensitive hyperpolarization rather than the usual depolarization. Protein I did not alter increments in [Ca]i (Fura-2) stimulated by fMLP (460 +/- 99 nM (S.E.) versus 377 +/- 44 nM) nor decrements in [pH]i (7.22 +/- 0.04 S.E. versus 7.22 +/- 0.02, bis-(carboxy-ethyl)carboxyfluorescein). The results suggest that degranulation and O2 generation have separate ionic requirements and that protein I interrupts the activation sequence proximal to activation of protein kinase C.
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PMID:Protein I, a translocatable ion channel from Neisseria gonorrhoeae, selectively inhibits exocytosis from human neutrophils without inhibiting O2- generation. 282 69

Circular dichroism studies on synthetic peptides corresponding to the signal sequences of chicken lysozyme and Escherichia coli proteins, lambda-receptor and lipoprotein, have been carried out in trifluoroethanol. The peptides, (CH3)3-C-O-CO-Thr-Leu-Lys-Lys-Leu-Pro-Leu-Ala-Val-Ala-Val-Ala-Ala-Gly- Val-Met-Thr-Ala- Ala-Met-Ala-OCH3, (CH3)3-C-O-CO-Met-Lys-Ser-Leu-Leu-Ile-Leu-Val-Leu-Cys(benzyl)- Phe-Leu-Pro- Leu-Ala-Ala-Leu-Gly-OH and (CH3)3-C-O-CO-Leu-Val-Leu-Gly-Ala-Val-Ile-Leu-Gly- Thr-Thr-Leu-Leu- Ala-Gly-OCH3, corresponding to the signal sequences of lambda-receptor, lysozyme and the hydrophobic region of lipoprotein, respectively, show two negative bands at approx. 205 and 220 nm, characteristic of an alpha-helical conformation. Secondary structural features are discernible even in the shorter, 12-residue carboxy-terminal fragments of these signal peptides. A comparison of the conformation of the amino-terminal, central and carboxy-terminal fragments of lipoprotein signal sequence indicates that the central octapeptide fragment is more structurally ordered compared to the amino- and carboxy-terminal fragments.
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PMID:Circular dichroism studies on synthetic signal peptides. 293 58

Activated human polymorphonuclear leukocytes (PMN) isolated from peripheral blood specifically bind 125I-laminin after stimulation with phorbol 12-myristate 13-acetate (PMA) or f-Met-Leu-Phe (FMLP) at 37 degrees C. Changes in laminin receptor expression are stimulus dose dependent at both chemotactic (10(-10) M to 10(-6) M) concentrations of FMLP, and secretory (greater than 5 ng/ml) levels of PMA. In the presence of cytochalasin B (5 micrograms/ml), 10(-7) M FMLP activation stimulates specific laminin binding, with an apparent Kd = 3.9 X 10(-9) M and 6.47 X 10(5) binding sites/cell, reaching equilibrium within 10 min at 4 degrees C. This observed activation-dependent change in laminin receptor expression is not due to interference by endogenous laminin, because no fluorescein-visualized anti-laminin antibody bound to cells without added glycoprotein, regardless of the level of activation. Levels of neutrophil lysozyme release, which show a PMA dose dependence similar to that of receptor binding activity, suggest that granule-plasma membrane fusion may be significant during increases in receptor expression. A lack of receptor stimulation by PMA from a granule-deficient patient or in granule-depleted cytoplasts from normal donors additionally supports this hypothesis. Electroblot transfer and autoradiography of subcellular fractions from unstimulated PMN reveals the presence of a 68,000 dalton laminin-binding component in the secondary/tertiary granule (beta) fraction, which may represent an intracellular laminin receptor pool.
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PMID:Human neutrophil laminin receptors: activation-dependent receptor expression. 294 78

The secretory response of cytochalasin B-treated human polymorphonuclear neutrophils to the peptide chemoattractant f-Met-Leu-Phe (FMLP), the calcium ionophore A23187 and other secretagogues was measured by assaying neutrophil supernatants for the granular enzymes beta-glucuronidase and lysozyme. The dose-dependent enzyme secretion in response to 10(-8)-10(-4) M FMLP and A23187 was unaffected by pretreatment with 10-75 microM forskolin (an activator of adenylate cyclase), but inhibited by high concentrations of prostaglandins E1 and E2. The phosphodiesterase inhibitors isobutyl-methyl-xanthine (IBMX), papaverine and Ro 20-1724 dose dependently inhibited enzyme secretion from FMLP- or A23187-treated cells, and this effect was augmented in the presence of 50-75 microM forskolin. Similar results for PGE1, forskolin and forskolin/IBMX combinations were also obtained using leukotriene B4, platelet activating factor and C5a des-Arg as secretagogues. We conclude that the adenylate cyclase system of human neutrophils is activatable by forskolin, but that the regulatory effects of adenylate cyclase stimulants in these cells are greatly attenuated unless cyclic AMP-phosphodiesterases are inhibited. Thus the phosphodiesterase activity of neutrophils may be of functional importance and is relevant to the modulation of neutrophil activity in inflammation.
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PMID:Inhibition of human neutrophil degranulation by forskolin in the presence of phosphodiesterase inhibitors. 301 41

Oxidative metabolism of polymorphonuclear leukocytes (PMNLs) isolated from pregnant women in the third trimester and from controls were studied using zymosan-induced chemiluminescence (CL) and f-Met-Leu-Phe-stimulated superoxide (O2-) generation. CL was significantly increased during pregnancy, but a decrease was noted in cytochrome c reduction. Total cellular levels of beta-glucuronidase and lysozyme were diminished in PMNLs from pregnant subjects, with unaltered concentrations of cytosol lactate dehydrogenase. The capacity of PMNLs from pregnant women to degranulate did not differ from controls. It is suggested that during pregnancy, in vivo stimulation of PMNLs may occur to account for these changes.
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PMID:Polymorphonuclear leukocyte response to stimulation in vitro during pregnancy. 301 55

The interaction of synthetic peptides corresponding to the signal sequences of Escherichia coli alkaline phosphatase: Lys-Gln-Ser-Thr-Ile-Ala-Leu-Ala-Leu-Leu-Pro-Leu-Leu-Phe-Thr-Pro-Val-Thr- Lys-Ala - OCH3, chicken lysozyme: Met-Lys-Ser-Leu-Leu-Ile-Leu-Val-Leu-Cys(Bzl)-Phe-Leu-Pro-Leu- Ala-Ala-Leu-Gly-OCH2-C6H5 and variant of the chicken lysozyme signal sequence with a charged residue in the hydrophobic region: Lys-Leu-Leu-Ile-Ala-Leu-Val-Leu-Lys-Phe-Leu-Pro-Leu-Ala-Ala- Leu-Gly-OCH3 with model membranes of brain phosphatidylserine (PS) and egg phosphatidylcholine (PC) have been investigated by 90 degrees light scattering and fluorescence spectroscopy. Our results indicate that the association of signal peptides with model membranes results in extensive perturbation of the lipid bilayer so as to cause fusion of PS vesicles and aggregation of PC vesicles. The vesicles are also rendered permeable to hydrophilic molecules like carboxyfluorescein. The variant peptide with the lysine residue in the hydrophobic region also has the ability to perturb lipid bilayers of model membranes.
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PMID:Perturbation of the lipid bilayer of model membranes by synthetic signal peptides. 331 Nov 64

To elucidate the structure-function relationship of the signal sequence for the secretion of human lysozyme by Saccharomyces cerevisiae, we have systematically engineered the hydrophobic segment using the signal sequence of chicken lysozyme. Replacement of Cys 10 with leucine caused a 1.6 times increase in the secretion of human lysozyme. An idealized signal sequence L10 in which 10 consecutive leucines were distributed from the 3rd to the 12th position was 1.8 times as effective as the native sequence. L10 can be generalized as Ln = Met-Arg-(Leu)n-Pro-Leu-Ala-Ala-Leu-Gly, where n = 10. We have also studied the secretory capability of Ln, where n = 6,8,12, and 14, and found that the length, as well as hydrophobicity, of the hydrophobic segment is an important factor in the secretion of human lysozyme by yeast.
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PMID:Engineering of the hydrophobic segment of the signal sequence for efficient secretion of human lysozyme by Saccharomyces cerevisiae. 332 76

In the preceding paper in this issue, we described the overproduction of one mutant chicken lysozyme in Escherichia coli. Since this lysozyme contained two amino acid substitutions (Ala31----Val and Asn106----Ser) in addition to an extra methionine residue at the NH2-terminus, the substituted amino acid residues were converted back to the original ones by means of oligonucleotide-directed site-specific mutagenesis and in vitro recombination. Thus, four kinds of chicken lysozyme [Met-1Val31Ser106-, Met-1Ser106-, Met-1Val31- and Met-1 (wild type)] were expressed in E. coli. From the results of folding experiments of the reduced lysozymes by sulfhydryl-disulfide interchange at pH 8.0 and 38 degrees C, followed by the specific activity measurements of the folded enzymes, the following conclusions can be drawn: (i) an extra methionine residue at the NH2-terminus reduces the folding rate but does not affect the lysozyme activity of the folded enzyme; (ii) the substitution of Asn106 by Ser decreases the activity to 58% of that of intact native lysozyme without changing the folding rate; and (iii) the substitution of Ala31 Val prohibits the correct folding of lysozyme. Since the wild type enzyme (Met-1-lysozyme) was activated in vitro without loss of specific activity, the systems described in this study (mutagenesis, overproduction, purification and folding of inactive mutant lysozymes) may be useful in the study of folding pathways, expression of biological activity and stability of lysozyme.
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PMID:Point mutation of alanine (31) to valine prohibits the folding of reduced lysozyme by sulfhydryl-disulfide interchange. 333 91

The effects of two co-carcinogenic phorbol esters (phorbol myristate acetate (PMA) and phorbol dibutyrate (PDBu] and a synthetic diacylglycerol (OAG, 1-oleoyl-2-acetyl-glycerol), which all stimulate protein kinase C, were compared with two inactive phorbol compounds (4 alpha-phorbol and 4 alpha-phorbol didecanoate (4 alpha-PDD)) on three functional properties of stimulated human polymorphonuclear leukocytes (PMNs): release of granular enzymes lysozyme and beta-glucuronidase, chemokinesis, and changes in cytoplasmic free calcium [Ca2+]i. PMA, PDBu and the diacylglycerol, OAG, all caused a dose-dependent and slow (max by 15 min) release of small amounts of lysozyme with much less beta-glucuronidase and no release of cytoplasmic lactate dehydrogenase. Release was unaffected by removal of extracellular Ca2+. PMA, PDBu and OAG inhibited random movement of the cells, did not cause chemokinesis and induced a slow reduction in the basal [Ca2+]i, as measured by the quin-2 method. PMA, PDBu and OAG increased the capacity of five independently-acting stimulants (N-formyl-Met-Leu-Phe, leukotriene B4, C5a des-Arg, platelet activating factor and A23187) to cause release of lysozyme and beta-glucuronidase but strongly inhibited PMN chemokinesis induced by the same five agents and reduced the stimulant-induced increases in [Ca2+]i. PMA was always more potent than PDBu and much more potent than OAG in eliciting these stimulatory or inhibitory effects on human PMNs. In all tests, 4 alpha-phorbol and 4 alpha-PDD were inactive. The results confirm that stimulation of the diacylglycerol/protein kinase C system in human PMN, either by active phorbol esters or the synthetic diacylglycerol, causes bidirectional effects on human PMN function. In particular, activation of the C-kinase causes inhibition of stimulated neutrophil motility, whereas the secretory functions of the cells are enhanced.
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PMID:Divergent effects of co-carcinogenic phorbol esters and a synthetic diacylglycerol on human neutrophil chemokinesis and granular enzyme secretion. 347 47

Analogs of chemotactic peptides (Formyl-Met-X-Phe-OMe) containing the stereochemically constrained residues alpha-aminoisobutyric acid (Aib), 1-aminocyclopentanecarboxylic acid (Acc5) and 1-aminocyclohexanecarboxylic acid (Acc6) at position 2 are compared with the parent sequence (X = Leu) for their ability to induce lysozyme release in rabbit neutrophils. The Acc6 analog is about 78 times more active than the parent peptide, For-Met-Leu-Phe-OH, whereas Aib and Acc5 analogs are approximately 3 and 2 times, respectively, less active than the parent peptide. NMR and model building studies clearly favour a Met-Acc6 beta-turn solution conformation in the Acc6 analog, suggesting that the neutrophil receptor is capable of recognizing a folded peptide structure. The significant differences in the activities of the Acc5 and Acc6 analogs suggest an important role for the residue 2 sidechain in receptor interactions.
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PMID:A highly active chemotactic peptide analog incorporating the unusual residue 1-aminocyclohexanecarboxylic acid at position 2. 398 73


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