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

---

Query: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The spore-coat fraction from Bacillus megaterium KM, when prepared by extraction of lysozyme-digested integuments with SDS (sodium dodecyl sulphate) and urea, contains three N-terminal residues and a major component of apparent mol.wt. 17500. Electron microscopy of this fraction shows it to consist of an ordered multilamellar structure similar to that which forms the coat region of intact spores. The 17500-dalton protein, which has been purified to homogeneity, has an N-terminal methionine residue, has high contents of glycine, proline, cysteine and acidic amino acids and readily polymerized even in the presence of thiol-reducing agents. It is first synthesized between late Stage IV and early Stage V, which correlates with the morphological appearance of spore coat. Before Stage VI the 17500-dalton protein is extractable from sporangia by SDS in the absence of thiol-reducing reagents. Between Stage VI and release of mature spores the protein becomes resistant to extraction by SDS unless it is supplemented by a thiol-reducing reagent. In addition to that of the spore-coat protein, the timing of synthesis of all the integument proteins was analysed by SDS/polyacrylamide-gel electrophoresis and non-equilibrium pH-gradient electrophoresis. Several integument proteins are conservatively synthesized from as early as 1h after the end of exponential growth (t1), which may reflect protein incorporation into the spore outer membrane.
...
PMID:Characterization, purification and synthesis of spore-coat protein in Bacillus megaterium KM. 680 68

Fumarase (EC 4.2.1.2) and mitochondrial L-malate dehydrogenase (EC 1.1.1.37) were both inhibited by NaAuCl4 and KAuBr4. The inhibition for both was measured as a function of gold complex concentration and aquation time, and the NaAuCl4 inhibition was also measured in the presence of 0.15 M NaCl. Regeneration of the enzyme activity after NaAuCl4 inhibition using L-cysteine, L-methionine and NaCN was also investigated. Sodium dodecyl sulfate (SDS) acrylamide gel electrophoresis and amino acid analysis was performed on the NaAuCl4 inhibited enzymes as well as on ribonuclease A (EC 3.1.26.2), lysozyme (EC 3.2.1.17) and liver alcohol dehydrogenase (EC 1.1.1.1). It was observed that the inhibition was proportional to the gold complex concentration but decreased markedly after aquation of the complex. In the presence of NaCl the initial rate of inactivation is essentially unaffected unless the complex has been aquated and then the initial rate is increased. Gel electrophoresis on gold complex-enzyme mixtures show polymerization for ribonuclease and lysozyme and amino acid analysis indicates that no oxidation has taken place. From these results, a binding mechanism is postulated for the inhibition of the dehydrogenases by direct displacement of a halide ligand, probably by two groups on the enzyme, at least one of which may be a sulfur containing acid.
...
PMID:Inhibition of two mitochondrial enzymes by gold (III) halo complexes. Evidence for a binding mechanism. 715 Dec 34

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.
...
PMID:Purification and characterization of biliverdin reductase from rat liver. 721 67

Eosinophils were isolated from the mammary gland of Fasciola hepatica-infected cattle by intramammary infusion with a crude extract from adult F. hepatica. Up to 5 x 10(9) eosinophils with a purity of over 90% could be obtained from a single quarter of the gland. The major contaminating cells were monocytes which reached their peak several days following the eosinophil peak. Two major proteins were isolated from bovine eosinophil granules, a high molecular weight peroxidase-active protein and a smaller molecular weight predominantly basic protein. This smaller protein was thought to be the bovine equivalent of guinea-pig and human major basic protein (MBP), although it possessed an unusually high concentration of cysteine. The bovine MBP had a profound effect on juvenile F. hepatica in vitro causing damage and death at concentrations down to 1 x 10(-6) M. The damage was detected by a 51Cr release assay and/or a viability assay involving microscopical examination of the flukes. Other cations, especially protamine sulphate, were also shown to kill flukes, although both lysozyme, found in neutrophils, and the peroxidase-positive peak from bovine eosinophils were unable to mediate any detectable damage.
...
PMID:Killing of juvenile Fasciola hepatica by purified bovine eosinophil proteins. 743 42

A method has been developed for preparation of an enzymically active two-disulfide bonded derivative from hen egg lysozyme. Lysozyme (0.15 mM) is incubated with 2 mM dithiothreitol at pH 7.8, 23 degrees for 40 min. The products are reacted with [1-14C]iodoacetic acid and then purified by gel filtration and ion-exchange chromatography. An enzymically active derivative containing 4 mol of [1-14C] carboxymethyl groups and no free sulfhydryl groups is obtained in approximately 18% yield. Examinations of hydrodynamic volume, tryptophan fluorescence, CD and tryptic peptides containing [1-14C] carboxymethyl cysteine indicate that this derivative contains two presumably native disulfide bonds and two open disulfide bonds between Cys 6 and Cys 127 and between Cys 76 and Cys 94. The rest of the species in the incubation mixture are intact lysozyme. Thus, the species containing two presumably native disulfide bonds and four free sulfhydryl groups at Cys 6, Cys 76, Cys 94 and Cys 127 appears to be only the intermediate accumulating during reduction of lysozyme with dithiothreitol.
...
PMID:Preparation of a two-disulfide bonded enzymically active derivative from hen egg lysozyme. 744 57

Beta-N-Acetylglucosaminidase has been purified from an acetone extract of Aspergillus niger. The protein has a Mr = 149,000. It contains neither Mn2+, Zn2+, nor cysteine and exhibits no cation requirement for activity. Isoelectric focusing separates two isozymes; the major isoenzyme has a pI = 4.4. Both isozymes exhibit beta-N-acetylgalactosaminidase and beta-glucosidase, as well as glucosaminidase activity. The mechanism of action of this enzyme has been studied in detail using a variety of substrate structure/activity and kinetic experiments. Rate data plotted versus pH depends on the following ionization constants, respectively: for pKm, 2.95; for log Kcat, 7.6; and for log kcat/Km, 2.95 and 8.25. The kcat value of H2O/D2O for p-nitrophenyl-beta-N-acetylglucosaminide hydrolysis is 1.27 at pH 4.6 and 1.00 at pH 7.0. The rho value for the hydrolysis of para-substituted phenylglucosaminides is +0.36; rho for the hydrolysis of fluoro-substituted N-acetyl derivatives is -1.41. Two sulfur-containing substrate analogues, the 1-thioglucosaminide, and the N-thioacetyl derivative, exhibit either no or little substrate activity. The hydrolysis of the 2,4-dinitrophenyl-glucosaminide is not biphasic as indicated by stopped flow kinetic studies. These several results are interpreted to show that: 1) enzymatic nucleophilic catalysis is not employed by beta-N-acetylglucosaminidase; 2) the glycosidic oxygen is protonated very early in the reaction, perhaps even in the Michaelis complex; 3) the acetamido oxygen provides anchimeric assistance to hydrolysis via charge stabilization of the oxocarbonium ion (or via oxazoline formation); 4) additional charge stabilization is provided by an enzymic anion, perhaps a side chain carboxylate group. The role of the acetamido group is discussed and comparisons are made between lysozyme, beta-galactosidase, and beta-N-acetylglucosaminidase.
...
PMID:Purification, properties, kinetics, and mechanism of beta-N-acetylglucosamidase from Aspergillus niger. 744 May 73

Why diabetes is associated with abnormally high susceptibility to infection remains unknown, although two major antibacterial proteins, lysozyme and lactoferrin, have now been shown to specifically bind glucose-modified proteins bearing advanced glycation end products (AGEs). Exposure to AGE-modified proteins inhibits the enzymatic and bactericidal activity of lysozyme, and blocks the bacterial agglutination and bacterial killing activities of lactoferrin. Peptide mapping revealed a single AGE binding domain in lysozyme and two AGE binding domains in lactoferrin; each domain contains a 17- to 18- amino acid cysteine-bounded loop motif (CX15-16C) that is markedly hydrophilic. Synthetic peptides corresponding to these motifs in lysozyme and lactoferrin exhibited AGE binding activity, and similar domains are also present in other antimicrobial proteins. These results suggest that elevated levels of AGEs in tissues and serum of diabetic patients may inhibit endogenous antibacterial proteins by binding to this conserved AGE-binding cysteine-bounded domain 'ABCD' motif, thereby increasing susceptibility to bacterial infections in the diabetic population.
...
PMID:Antibacterial activity of lysozyme and lactoferrin is inhibited by binding of advanced glycation-modified proteins to a conserved motif. 748 52

Light microscopy and transmission electron microscopy of thin sections and metal-shadowed specimens showed that the sheath of Leptothrix discophora SP-6 (ATCC 51168) is a tube-like extracellular polymeric structure consisting of a condensed fabric of 6.5-nm-diameter fibrils underlying a more diffuse outer capsular layer. In thin sections, outer membrane bridges seen to contact the inner sheath layer suggested that the sheath fabric was attached to the outer layer of the gram-negative cell wall. The capsular polymers showed an affinity for cationic colloidal iron and polycationic ferritin, indicating that they carry a negative charge. Cell-free sheaths were isolated by treatment with a mixture of lysozyme, EDTA, and N-lauroylsarcosine (Sarkosyl) or sodium dodecyl sulfate (SDS). Both Sarkosyl- and SDS-isolated sheaths were indistinguishable in microscopic appearance. However, the Mn-oxidizing activity of Sarkosyl-isolated sheaths was more stable than that of SDS-isolated sheaths. The Sarkosyl-isolated sheaths also contained more 2-keto-3-deoxyoctanoic acid and more outer membrane protein than SDS-isolated sheaths. The oven-dried mass of detergent-isolated sheaths represented approximately 9% of the total oven-dried biomass of SP-6 cultures; the oven-dried sheaths contained 38% C, 6.9% N, 6% H, and 2.1% S and approximately 34 to 35% carbohydrate (polysaccharide), 23 to 25% protein, 8% lipid, and 4% inorganic ash. Gas-liquid chromatography showed that the polysaccharide was an approximately 1:1 mixture of uronic acids (glucuronic, galacturonic, and mannuronic acids and at least one other unidentified uronic acid) and an amino sugar (galactosamine). Neutral sugars were not detected. Amino acid analysis showed that sheath proteins were enriched in cysteine (6 mol%). The cysteine residues in the sheath proteins probably provide sulfhydryls for disulfide bonds that play an important role in maintaining the structural integrity of the sheath (D. Emerson and W.C. Ghiorse, J. Bacteriol. 175:7819-7827, 1993).
...
PMID:Ultrastructure and chemical composition of the sheath of Leptothrix discophora SP-6. 750 63

The interaction between proteins and a radiological commonly-used contrast medium (iopamidol) have been studied by calorimetry. When aqueous solutions of fibrinogen or of lysozyme (20 g/l) are mixed with an aqueous solution of iopamidol (1,3-5 benzendicardoxamid,N,N'-bis[2-hydroxy-1-(hydroxymethyl)ethyl]-5- [(2-hydroxy-1-oxopropyl)amino]-2,4,6-triiodo) in the clinical blood concentration range (26-485 mM), isothermal calorimetry reveals a weak endothermal interaction at a high concentration of iopamidol for both proteins. This endothermal effect does not appear to be due to direct protein-iopamidol association. Differential scanning calorimetry confirms the influence of iopamidol by the change in protein unfolding in the presence of contrast medium, and suggests alterations in the protein solvation as a mechanism. Dilution studies indicate that iopamidol can influence protein solvation even when water molecules are present in a molecular excess of 1000. The influence of iopamidol on the availability of water molecules and the absence of direct interaction with the protein molecules is shown by Raman spectroscopy of two amino acids in the presence of iopamidol. The spectrum of alanine is unchanged at any iopamidol concentration studied, whereas the spectrum lines due to the thiol group of cysteine are shifted in a manner consistent with altered solvation.
...
PMID:Involvement of protein solvation in the interaction between a contrast medium (iopamidol) and fibrinogen or lysozyme. 770 52

Micromites (genus Dermatophagoides) are the major source of allergens in house dust. Four homologous classes of major allergens have been isolated from extracts of D. pteronyssinus and D. farinae mites. According to current theories, all major mite allergens are proteins of gastrointestinal origin. Group I mite allergens, Der pI and Der fI, are thermolabile glycoproteins with M(r) of 25 kDa. A comparison of primary structure of these proteins reveals a 30% homology with cathepsins B and H, papain and actinidine. Analysis of enzymatic activities reveals that group I allergens are proteolytic enzymes related to the class of cysteine proteinases. With regard to antigenic composition, Der pI and Der fI have three common and two species-specific epitopes. The amino acid sequence of the major allergenic determinant for Der pI has been established. Group II mite allergens, Der pII and Der fII, are single-chain thermostable proteins with M(r) of 10-14 kDa and are said to bear many common features with the lysozyme. Group III mite allergens are analogous to trypsin. A 50% homology of amino acid sequences of Der pIII and Der fIII to those of vertebrate and invertebrate serine proteinases has been found. To the fourth group of major mite allergens one may relate mite amylase (M(r) = 56-60 kDa). A high degree of homology has been established between group IV allergens and mammalian alpha-amylase. Mite allergens of all groups induce the production of specific IgE antibodies in human organism. The use of purified allergens increases the efficiency of diagnosis and treatment of mite-induced allergoses. Modified forms of mite allergens (allergoids, allergens adsorbed on carriers, liposome preparations, etc.) are helpful tools in specific immunotherapy.
...
PMID:[Allergens from Dermatophagoides dust mites: origin, antigenic and structural characteristics, and therapeutic agents]. 771 66


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---