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)

Optimal conditions for detecting staphylokinase, phosphatase, protease, lipase, esterase, egg yolk factor, lysozyme, deoxyribonuclease, hyaluronidase, penicillinase, and alpha-, beta-, and delta-hemolysins in cell-free filtrates of selected strains of staphylococci by agar plate methods were established by studying the effect of factors such as buffer composition, pH, ionic strength, type of agar, nature and concentration of substrate, and certain metal ions. The final tests that evolved from this study are simple to perform, require only 6 mul of the sample per test, and are capable of detecting microgram and, in some cases, nanogram quantities of the product. The zones of reaction can also be quantitatively related to the amount of material present. The test may also be useful for the detection of extracellular products of other microorganisms.
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PMID:Agar plate tests of enhanced sensitivity for detecting biologically active products of staphylococcal filtrates. 18 61

The extracellular production of hyaluronidase and chondroitin sulfatase was demonstrated in all of the subspecies of Bacteroides fragilis tested with the exception of B. fragilis subsp. vulgatus. Elastase was found only in one strain of B. coagulans tested. This appears to be the first report of these enzyme activities in this genus. Additional enzymes found to be produced by certain members othis genus were fibrinolysin, penicillinase, lysozyme, lecithinase, deoxyribonuclease, phosphatase, protease, and lipase.
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PMID:Extracellular enzymes of the genus Bacteroides. 18 84

Three methods at present available for the purification of staphylococcal delta-haemolysin were compared as to the purity and identify of the product obtained. None yielded a pure preparation of delta-haemolysin; one of the three preparations did not contain demonstrable delta-haemolysin when tested electrophoretically, but it contained deoxyribonuclease, penicillinase, phosphatase and alpha-haemolysin. The second preparation had delta-haemolysin activity and was free of alpha-haemolysin, but it contained lipase, egg-yolk factor, esterase, deoxyribonuclease, penicillinase, phosphatase and hyaluronidase. The third preparation contained all of the products mentioned above, except phosphatase, and it also contained alpha-haemolysin, staphylokinase, lysozyme and caseinase. These findings are discussed with special reference to the requirement for criteria of purity in work with staphylococcal products.
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PMID:Purity of staphylococcal delta-haemolysin obtained by three different procedures. 18 51

The degree of peptidoglycan cross-linking has been studied in growing cells of a Dap(-) Lys(-) auxotroph of Escherichia coli K-12 by following the incorporation of [(3)H]diaminopimelic acid into the lysozyme digestion products of crude, isolated peptidoglycan. The percentage of inhibition of cross-linking increases with increasing concentrations of penicillin G, cephaloridine, and cefuroxime. When the R factor R1drd 19 was introduced into the strain by conjugation, it was found that the type IIIa, beta-lactamase specified by the plasmid was able to protect the cross-linking target against inhibition by penicillin G but not against cephaloridine, even though the beta-lactamase hydrolyzes this substrate 50% faster than penicillin G. Cefuroxime, which is completely resistant to hydrolysis by the type IIIa beta-lactamase, inhibited the peptidoglycan cross-linking target in both the R(+) and R(-) variants of the assay strain. A mutant plasmid, R1drd19amp2, which specified no type IIIa beta-lactamase synthesis, could not provide protection of the cross-linking target against penicillin G. The significance of these results, in relation to the ability of the antibiotics to pass the permeability barrier of the bacterial envelope, is discussed.
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PMID:Inhibition of peptidoglycan cross-linking in growing cells of Escherichia coli by penicillins and cephalosporins, and its prevention by R factor-mediated beta-lactamase. 77 94

With TEM beta-lactamase as a reporter gene, a set of expression-secretion-promoting fragments were isolated from the chromosome of Lactococcus lactis subsp. lactis. The fact that only translocated beta-lactamase renders cells resistant to ampicillin allowed direct ampicillin selection with an Escherichia coli vector (pKTH33). The clones showing the greatest ampicillin resistance were subcloned onto a replicon capable of replication in lactic acid bacteria (pVS2), and the nucleotide sequences of the relevant fragments were determined. The structure of the secretion-promoting fragments in general resembled that of gram-positive true signal sequences, with a strongly positively charged N terminus, a long hydrophobic core, and a putative signal peptidase recognition site. The promoterlike sequences preceding the signal sequences matched well with those of previously published lactococcal promoters. In addition to E. coli, the functioning of these expression-secretion cassettes was studied in three gram-positive hosts: Bacillus subtilis, L. lactis, and Lactobacillus plantarum. Efficient expression and secretion of TEM beta-lactamase into the culture medium of each gram-positive host was obtained. Furthermore, when a strain of L. lactis subsp. lactis showing increased sensitivity to lysozyme was compared with a standard laboratory strain, threefold-higher secreted enzyme activities were detected.
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PMID:Secretion of TEM beta-lactamase with signal sequences isolated from the chromosome of Lactococcus lactis subsp. lactis. 190 4

Previous work ascribed antibiotic hypersensitivity of the envA1 mutant to lowered lipopolysaccharide levels and exposure of the lipid bilayer. In the detailed characterization of the EnvA permeability phenotype presented here, the envA1 mutation was shown to confer leakage of the periplasmic enzymes beta-lactamase and RNase I. Leakage was observed in three different genetic backgrounds, including the original envA1 strain and its parent. In contrast, no detectable leakage of the cytoplasmic enzyme beta-galactosidase was observed. Sensitivity of envA1 strains to a range of antibiotics not previously reported was tested, and lipophilicity (partition coefficient) of a number of antibiotics was determined. On the basis of observations of periplasmic leakage and sensitivity to large hydrophilic antibiotics and lysozyme, part of the permeability phenotype of the envA1 mutant is proposed to be due to transient rupture and resealing of the EDTA-sensitive outer membrane layer. In this regard, the EnvA permeability phenotype falls into a general class of permeability/leaky mutants of both Escherichia coli and Salmonella typhimurium.
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PMID:Leakage of periplasmic enzymes from envA1 strains of Escherichia coli. 190 54

An efficient fusion system between Gram-negative bacteria and liposomes incorporating detergent-extracted C5b-9 complexes has been developed that allows delivery of preformed terminal complexes to the cell envelope (Tomlinson et al., 1989b). Fusion of Salmonella minnesota Re595 and Escherichia coli 17 with C5b-9-incorporated liposomes resulted in the transfer of 1900 C5b-9 complexes to each target bacterial cell. No loss in viability of bacteria was observed following fusion, even though the deposotion of 900 complexes onto the envelope following exposure to lysozyme-free serum effected a greater than 99% loss of viability. Increased sensitivity to antibiotics normally excluded from the cell by an integral outer membrane (OM), as well as the ability of the chromogenic substrate PADAC to gain access to periplasmically located beta-lactamase, indicated that transferred C5b-9 complexes functioned as water-filled channels through the OM. A similar conclusion was drawn from measurements demonstrating the uptake by cells of the lipophilic cation tetraphenylphosphonium (bromide), a result further indicating that the membrane potential across the cytoplasmic membrane was maintained following C5b-9 transfer to the OM. Examination of S. minnesota Re595 by electron microscopy revealed no obvious difference between cells exposed to lethal concentrations of lysozyme-free serum and cells following fusion with C5b-9-incorporated liposomes. These data suggest either that there are critical sites in the OM to which liposome-delivered C5b-9 complexes are unable to gain access or that bacterial cell death is related to events occurring during polymerization of C9 on the cell surface.
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PMID:Transfer of preformed terminal C5b-9 complement complexes into the outer membrane of viable gram-negative bacteria: effect on viability and integrity. 218 89

Growth of methicillin-resistant Staphylococcus aureus DU4916 in the presence of methicillin yielded crude cell walls that showed an increased rate of autolysis and purified cell walls (PCW) and peptidoglycan (PG) that had increased susceptibilities to autolysin extracted with LiCl and to lysozyme. The PG of cells grown in the presence of methicillin had markedly decreased cross-linking and O acetylation. Growth of the methicillin-susceptible strain H in the presence of subinhibitory concentrations of cefoxitin, a specific inhibitor of penicillin-binding protein (PBP) 4, caused a substantial decrease in PG cross-linking and O acetylation and increased susceptibilities of PCW and PG to LiCl-extracted autolysin and to lysozyme. Strain DU4916 cells grown in the presence of methicillin did not show an increased rate of autolysis or an increased susceptibility to vancomycin- or D-cycloserine-induced lysis, even though their PG was hypo-cross-linked. This implies that the potential for increased autolysis is controlled in intact cells and that this regulation may be involved in the methicillin resistance phenomenon. Growth of the methicillin-susceptible strain DU4916S in the presence of methicillin yielded PCW and PG that showed small increases in susceptibilities to LiCl-extracted autolysin and to lysozyme and a small decrease in PG cross-linking. Comparison of the PBPs of a penicillinase-nonproducing derivative of strain DU4916 (DU4916-K7) with those of strain DU4916S in intact cells and isolated membranes revealed that PBPs 1 to 4 had similar high beta-lactam antibiotic affinities in both strains and identified an additional PBP, PBP2(1), with low beta-lactam affinity in the methicillin-resistant strain DU4916-K7. The low degree of cross-linking of PG in strain DU4916 cells grown with methicillin was probably due mainly to inhibition of the secondary cross-linking function of PBP 4.
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PMID:Effects of growth of methicillin-resistant and -susceptible Staphylococcus aureus in the presence of beta-lactams on peptidoglycan structure and susceptibility to lytic enzymes. 287 55

We have shown recently that an average of three or more C9 molecules must bind to C5b-8 on Escherichia coli strain J5 to cause direct complement killing in the absence of serum lysozyme. We initially confirmed and extended this observation by showing that deposition of a large number of C5b-9 complexes bearing 1C9 per C5b-8 was not bactericidal for J5. To identify the target site for bactericidal C5b-9 deposition, we measured release of periplasmic and cytoplasmic markers of different size from J5 as the C9:C5b-8 ratio was changed, because the diameter of the C5b-9 channel is known to increase as the C9:C5b-8 ratio increases. To facilitate measurement of release of the periplasmic marker beta-lactamase (BLA), J5 was transformed for high level constitutive TEM-1 BLA production (J5-Amp). Multimeric C9 within C5b-9 (C9:C5b-8 greater than 3) was required to release BLA (m.w. 28,900) from J5-Amp regardless of whether cells bore 310, 560, or 890 C5b-9/organism. Curves of both BLA release and killing vs C9:C5b-8 ratio were sigmoidal and nearly superimposable. Release of the small cytoplasmic marker 86Rb, a potassium analog, also required a minimum C9:C5b-8 ratio of 3:1; specific 86Rb release did not occur in the absence of killing. Release of the large cytoplasmic marker beta-galactosidase (m.w. 505,000) did not occur even at the highest achievable C9:C5b-8 ratio of 11:1, despite greater than 99.9% killing, indicating that there was no dissolution of the peptidoglycan layer due to incomplete removal of serum lysozyme. Complement-mediated killing of J5 requires sufficient damage to the outer membrane or formation of a sufficiently large C5b-9 channel to release the large periplasmic marker BLA. The requirement of multimeric C9 for 86Rb release suggests that at low C9:C5b-8 ratios, either C5b-9 does not have access to the cytoplasmic space or that the J5 K+ transport systems are able to compensate for putative C5b-9 channels.
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PMID:Multimeric C9 within C5b-9 is required for inner membrane damage to Escherichia coli J5 during complement killing. 310 Jun 18

Overexpression of Bacillus stearothermophilus gene coding for thermostable alpha-amylase in Escherichia coli was shown to cause outer-membrane damage leading to extracellular location of periplasmic proteins. Prolonged high expression of the alpha-amylase gene under lacZpo control eventually also lysed cells. Surprisingly, expression controlled by the pL promoter of phage lambda allowed specific release of periplasmic proteins into the growth medium without total cell lysis. Accumulation of alpha-amylase in the growth medium continued for at least 24 h under lambda pL control, whereas beta-lactamase activity ceased to increase beyond the exponential growth phase. The extent of outer membrane damage caused by alpha-amylase expression was monitored by following growth kinetics in the presence of lysozyme and by electron microscopy of the cells. Supplementing growth medium with Mg2+ restored the normal growth kinetics. It is suggested that periplasmic protein release caused by alpha-amylase overexpression is a stress response of the cell. A role for induced autolytic activity of the cell as a final effector of protein release is also proposed.
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PMID:Extracellular production of cloned alpha-amylase by Escherichia coli. 332 55


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