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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some Bacillus subtilis strains, including natto (fermented soybeans) starter strains, produce a capsular polypeptide of glutamate with a gamma-linkage, called poly-gamma-glutamate (gamma-PGA). We identified and purified a monomeric 25-kDa degradation enzyme for gamma-PGA (designated gamma-PGA hydrolase, PghP) from bacteriophage PhiNIT1 in B. subtilis host cells. The monomeric PghP internally hydrolyzed gamma-PGA to oligopeptides, which were then specifically converted to tri-, tetra-, and penta-gamma-glutamates. Monoiodoacetate and EDTA both inhibited the PghP activity, but Zn(2+) or Mn(2+) ions fully restored the enzyme activity inhibited by the chelator, suggesting that a cysteine residue(s) and these metal ions participate in the catalytic mechanism of the enzyme. The corresponding pghP gene was cloned and sequenced from the phage genome. The deduced PghP sequence (208 amino acids) with a calculated M(r) of 22,939 was not significantly similar to any known enzyme. Thus, PghP is a novel gamma-glutamyl hydrolase. Whereas phage PhiNIT1 proliferated in B. subtilis cells encapsulated with gamma-PGA, phage BS5 lacking PghP did not survive well on such cells. Moreover, all nine phages that contaminated natto during fermentation produced PghP, supporting the notion that PghP is important in the infection of natto starters that produce gamma-PGA. Analogous to polysaccharide capsules, gamma-PGA appears to serve as a physical barrier to phage absorption. Phages break down the gamma-PGA barrier via PghP so that phage progenies can easily establish infection in encapsulated cells.
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PMID:Characterization of poly-gamma-glutamate hydrolase encoded by a bacteriophage genome: possible role in phage infection of Bacillus subtilis encapsulated with poly-gamma-glutamate. 1273 13

The immunomodulatory effect of GMP and its derivates on the cell proliferative response of human macrophagelike cell, U937, and its effect on phagocytic activities via incorporation of fluorescence beads were studied. GMP was found to be a potent immunoenhancer at low concentrations, significantly enhancing the proliferation and phagocytic activities of U937. The modulatory function could be radically altered by enzymatic treatments. Pepsin digestion significantly enhanced the degree of cell proliferation and phagocytic activities, whereas trypsin had no significant effect. The immunoenhancing effects decreased significantly after sialidase treatment; however, more than 70% of activity was retained after treatment. GMP with different carbohydrate chains was shown to possess different modulatory capabilities. Sialic acid-rich GMP fractions showed an enhanced response. These findings indicate that both the carbohydrate chains compositions, including the terminal sialic acids and the polypeptide portions of GMP, are essential for the stimulatory effects of GMP on cell proliferation and phagocytic activities of U937.
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PMID:Immunoenhancing effects of bovine glycomacropeptide and its derivatives on the proliferative response and phagocytic activities of human macrophagelike cells, U937. 1511 79

Many bacteria, including Escherichia coli, have a unique gene that encodes glutamate racemase. This enzyme catalyses the formation of d-glutamate, which is necessary for cell wall peptidoglycan synthesis. However, Bacillus subtilis has two glutamate racemase genes, named racE and yrpC. Since racE appears to be indispensable for growth in rich medium, the role of yrpC in d-amino acid synthesis is vague. Experiments with racE- and yrpC-knockout mutants confirmed that racE is essential for growth in rich medium but showed that this gene was dispensable for growth in minimal medium, where yrpC executes the anaplerotic role of racE. LacZ fusion assays demonstrated that racE was expressed in both types of media but yrpC was expressed only in minimal medium, which accounted for the absence of yrpC function in rich medium. Neither racE nor yrpC was required for B. subtilis cells to synthesize poly-gamma-dl-glutamate (gamma-PGA), a capsule polypeptide of d- and l-glutamate linked through a gamma-carboxylamide bond. Wild-type cells degraded the capsule during the late stationary phase without accumulating the degradation products, d-glutamate and l-glutamate, in the medium. In contrast, racE or yrpC mutant cells accumulated significant amounts of d- but not l-glutamate. Exogenous d-glutamate utilization was somewhat defective in the mutants and the double mutation of race and yrpc severely impaired d-amino acid utilization. Thus, both racemase genes appear necessary to complete the catabolism of exogenous d-glutamate generated from gamma-PGA.
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PMID:Roles and regulation of the glutamate racemase isogenes, racE and yrpC, in Bacillus subtilis. 1534 50

Sodium poly(gamma-glutamic acid) (PGA), a water-soluble and biodegradable polypeptide, was reacted with polyvinyl alcohol (PVA) to form hydrogel without any chemical treatment. The gelation occurred probably due to physical cross-linking of polymer chains by interpenetrating hydrogen bonding. From the results of thermal analysis, PGA/PVA exhibited better thermal stability than native PVA. Although the swelling ratio decreased with the increase of PGA content, however, the water resistance and retention were improved. The tensile strength of the PGA/PVA hydrogel membranes was about 15-30% lower than that of the native PVA, whereas the elongation was increased 2.0-2.6 times. The amount of protein adsorbed and platelets adhered on the PGA/PVA membranes were significantly curtailed with increasing PGA content, thereby showing improved blood compatibility. The as-fabricated hydrogels were proven to be non-cytotoxic evaluated in vitro by L-929 fibroblast incubation. Overall results demonstrate that the non-cytotoxic PGA/PVA hydrogels, due to better water resistance, mechanical properties and blood compatibility could be very promising candidates for blood-contacting medical devices.
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PMID:Blood compatibility of novel poly(gamma-glutamic acid)/polyvinyl alcohol hydrogels. 1638 82

The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.
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PMID:Immobilization of enamel matrix derivate protein onto polypeptide multilayers. Comparative in situ measurements using ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry. 1715 85

One pepsinogen C gene was cloned from the gastric mucosa of orange-spotted grouper (Epinephelus coioides) for the first time. This gene consisted of nine exons interrupted by eight introns. The nucleotide sequence with the coding region and 3'-flanking region was also determined. The deduced polypeptide sequence was composed of a prosegment of 55 residues and a pepsin moiety of 332 residues. The putative substrate-binding subsites were well conserved among fish with the exception of the residue Thr292 in the S(2) subsite and displayed a significantly low value of hydropathy and high flexibility. These differences may affect the catalytic function and substrate specificity. RT-PCR assay followed by Southern blot revealed that pepsinogen C was primarily distributed in the stomach, but also expressed in various tissues, including gill, intestine, pyloric ceca, esophagus and ovary. This is the first observation of pepsinogen C expression in various tissues of one species of fish. Pepsinogen C transcript was first detected at 41 dph and continuously expressed through to adult fish, coinciding with the pepsin-like enzymes activity during developmental stages. Pepsin-like enzymes activity was present in the early larva stage, increased significantly at the end of juvenile stage and remained at similar levels in young fish and adult. Northern blot analysis suggested that three forms of transcripts were expressed differently during experimental periods. Our results suggest that pepsin C possesses any other functions besides digestion.
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PMID:Characterization and expression of the pepsinogen C gene and determination of pepsin-like enzyme activity from orange-spotted grouper (Epinephelus coioides). 1797 66

The buildup mechanism of polypeptide multilayers prepared by the layer-by-layer deposition of a polyanion (poly(L-glutamic acid) (PGA)) and polycations (poly(L-lysine) (PLL), poly(D-lysine) (PDL), and copoly(DL-lysine)(PDLL)) was reinvestigated by using in situ ATR-IR spectroscopy. A difference spectral technique applied to analyze the spectra indicated that the deposition of both the PGA and PLL (PDL) layers accompanies the formation of secondary structures consisting mainly of the antiparallel pleated sheet (the beta-sheet) structure, and that the formation of the beta-sheet structure cannot always be explained in terms of polyanion/polycation complex formation or charge compensation between the polyanion and polycations, although it has been considered as a major process in the multilayer buildup process. Instead, the present paper proposes the following mechanism. During the deposition of the polyelectrolyte, a small amount of the beta-sheet structures are produced at the interface as a result of charge compensation between a polyelectrolyte and an oppositely charged polyelectrolyte in the multilayer. The beta-sheets act as nuclei from which further propagation of the structure takes place at the solution/multilayer interfaces. The driving force of the buildup process in the new mechanism is a kinetically favorable insolubilization of each polyelectrolyte in solution at the interfaces.
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PMID:Reinvestigation on the buildup mechanism of alternate multilayers consisting of poly(L-glutamic acid) and poly(L-, D-, and DL-lysines). 1897 12

Many recognition events important in biology are mediated via multivalent interactions between relevant oligosaccharides and multiple saccharide receptors present on lectins, viruses, toxins, and cell surfaces. Because of the important role played by protein-carbohydrate interactions in these pathogenic recognition events and in other human diseases, considerable effort has been devoted toward the development of multivalent polymeric ligands for carbohydrate-binding proteins. In this work, we report the synthesis of new polypeptide-based glycopolymers produced via a combination of protein engineering and chemical methods. These methodologies permit control over the number and the spacing of saccharides on the scaffold, as well as the conformation of the polymer backbone, and allow a more purposeful design of polymers for manipulation of multivalent binding events. Two families of galactose-bearing glycopolypeptides with random coil conformations, [(AG)(3)PEG](y) (y = 10 and 16) and {[(AG)(2)PSG](2)[(AG)(2)PEG][(AG)(2)PSG](2)}(y) (y = 6), have been synthesized. The carboxylic acid functionality of the glutamic acid residues allowed subsequent modification with amino-saccharides to yield the desired glycopolypeptides; selective placement of the glutamic acid group permitted investigation of the effects of multivalency and saccharide spacing on toxin inhibition. In addition, a family of galactose-functionalized PGA-based glycopolymers of varying molecular weights was also synthesized to compare the effects of backbone flexibility and hydrodynamic volume, relative to the recombinant glycopolypeptides, on toxin inhibition. Glycopolypeptides were characterized via (1)H NMR, MALDI-TOF mass spectrometry, SDS-PAGE analysis, and spectrophotometric assays. They were tested as inhibitors of the binding of the cholera toxin B subunit via direct enzyme-linked assays. The data from these experiments confirm the relevance of appropriate saccharide spacing on controlling the binding event and also indicate the influence of chain extension in improving inhibition.
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PMID:Effects of Saccharide Spacing and Chain Extension on Toxin Inhibition by Glycopolypeptides of Well-Defined Architecture. 1916 74

We reported the stepwise formation of biocompatible poly(L-lysine)/poly(L-glutamic acid) (PLL/PGA) multilayer films on mesoporous silica (MS) spheres via layer-by-layer (LbL) self-assembly technique. In-situ QCM revealed the nonlinear (exponential) growth of PLL/PGA multilayer films at both pH 5.5 and pH 7.0 conditions. Xi-potential measurements of the multilayer coated particles indicated that the multilayer surface was being charge-overcompensated in each adsorption step, thereby facilitating adsorption of the next oppositely charged polypeptide onto the MS spheres. Hollow polypeptide capsules could be obtained by subsequently removing silica cores in HF solution. By using enzyme-preloaded MS spheres as capsule templates, a general approach was developed for encapsulating enzymes in biocompatible microcapsules with high loading and retained bioactivity. The loading amount for several enzymes with different sizes and their bioactivity after encapsulation were also reported.
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PMID:Biocompatible polypeptide microcapsules via templating mesoporous silica spheres. 1922 40

Molecular dynamics simulations demonstrate that differences in the interaction of sodium and potassium with the carboxylate side chains of alpha-poly-L-glutamate (alpha-PGA) have a dramatic effect on the conformational properties of the polypeptide. Potassium ions cluster mainly in the second and third solvation shells of alpha-PGA because their low charge density makes the electrostatic interactions between them and alpha-PGA too weak for K(+) to compete with water for the first solvation shell of the alpha-PGA glutamic acid residuals. Unlike sodium ions, they do not switch the conformation of alpha-PGA from extended to alpha-helical. Potentials of mean force for pure water, sodium ion solutions, and potassium ion solutions show marked differences in ion association behavior. This supports the idea that Hofmeister effects depend upon direct ion-macromolecule interactions as well as interactions with water molecules in the first solvation shell rather than bulk water structuring.
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PMID:To switch or not to switch: the effects of potassium and sodium ions on alpha-poly-L-glutamate conformations in aqueous solutions. 1961 52


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