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

The rate of degradation of poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG), poly(L-glutamic acid) (PGA) and poly[HEG-co-GA] random copolymers by papain was measured in the pH range 4.0-7.5, employing the gel permeation chromatography method. The effect of the degree of ionization on the polymer conformation was measured by circular dichroism (c.d.). PHEG, which is uncharged, had a random coil conformation and an almost constant degradation rate within the whole pH interval. The ionization of PGA increased with increasing pH and was accompanied by conformational transition from helix to random coil. The hydrolysis of PGA by papain depended on pH with the optimum at about pH 5, indicating that both the high content of helix (at pH less than 5) and increasing charge density (at pH greater than 5), decreased the degradation rate. Contrary to PGA, pH profiles of the degradation rate of poly[HEG-co-GA] copolymers are monotonous and do not decrease at pH less than 5. In the copolymers the HEG residues act as a helix breaker and limit the formation of helical conformation. The role of structural features of a macromolecular substrate, i.e. the charge, helical conformation and the nature of amino acid residues, in the interaction between enzyme and polymer is discussed.
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PMID:Degradation of N5-(2-hydroxyethyl)-L-glutamine and L-glutamic acid homopolymers and copolymers by papain. 198 24

Poly(L-glutamic acid) (PGA) suppresses the polymerization of porcine brain microtubule proteins and induces the depolymerization in vitro in a concentration-dependent manner. The extent of inhibition increases with increasing molecular weight of the PGA tested. A 50% inhibition of the protein polymerization was observed at a PGA (molecular weight = 60,000) to microtubule protein ratio of 0.04 (w/w), and complete inhibition was obtained at a ratio of 0.07. Such an inhibition on the polymerization by PGA is greatly decreased when Mg2+ is present at a higher concentration. The addition of PGA raises the critical concentration of microtubule proteins necessary for assembly. During incubation with PGA, microtubule proteins retain the ability to assemble, i.e., substoichiometric amounts of taxol considerably relieve the inhibition of assembly by PGA. PGA interacts with microtubule-associated proteins (MAPs) preferentially, because the amount of MAPs binding to PGA-Sepharose 4B is much larger than that of tubulin. Tau proteins were observed only in adsorbed fractions, while MAP-2 was present in both unbound and adsorbed fractions.
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PMID:Inhibition of microtubule assembly by poly(L-glutamic acid) and the site of its action. 242 86

Bacillus licheniformis ATCC 9945A was cultivated in shake flasks using citrate (12 gl-1), glutamate (20 gl-1) and glycerol (80 gl-1) as carbon sources for cell growth and gamma-poly(glutamic acid) (gamma-PGA) production. The effect of the MnSO4 concentration in the medium over a range from 0.0 to 615 microns was studied. The number of viable cells increased for all concentrations of MnSO4 from approximately 10(5) to 10(9) colony-forming units (cfu) ml-1 by the early stationary phase (24 h). However, after 50 h, the cell viability decreased rapidly for relatively lower MnSO4 concentrations (0.615 and 0 microns). The utilization of carbon sources by B. licheniformis was greater for cultures containing 33.8 and 615 microns MnSO4 relative to cultures with no added MnSO4. For example, cultures with 615 microns MnSO4 utilized 37, 54 and 93% and cultures with no added MnSO4 utilized 19, 10 and 17% of glutamate, glycerol and citrate, respectively. The gamma-PGA volumetric yield increased from approximately 5 to 17 gl-1 for corresponding increases in MnSO4 concentration from 0 to 33.8 microns and then decreased at higher MnSO4 concentrations. The stereochemical content of gamma-PGA was found to vary inversely with MnSO4 concentration, and ranged from 59 to 10% L-glutamate units for MnSO4 concentrations of 0 and 615 microns, respectively. For all of the MnSO4 concentrations investigated, the gamma-PGA molecular weights decreased rapidly as the gamma-PGA volumetric yield simultaneously increased for cultivation times from 24 to approximately 50 h. Mw and Mn values after approximately 50 h cultivation times, determined by gel permeation chromatography (GPC), were 1.3 to 1.6 and 0.5 to 0.8 million g mol-1, respectively. A complex gamma-PGA molecular weight distribution that appeared bimodal by GPC analysis due to the presence of a low-molecular-weight product fraction was observed in cultures containing 33.8 and 61.5 microns MnSO4 at extended cultivation times. A high-molecular-weight fraction and the unfractionated gamma-PGA sample from the 33.8 microns MnSO4 culture contained 13 +/- 4 and 30 +/- 1% L-repeat units, respectively. A relationship between the product molecular weight and its stereochemical composition was thus established.
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PMID:Effects of manganese (II) on Bacillus licheniformis ATCC 9945A physiology and gamma-poly(glutamic acid) formation. 858 90

Two isozymes of gamma-glutamyltranspeptidase, GGT-A and GGT-B, were purified to electrophoretic homogeneity from a culture broth of Bacillus subtilis TAM-4, which produces poly(gamma-glutamic acid) (PGA) de novo. GGT-A was composed of three subunits with molecular weights of 23,000 (I), 39,000 (II), and 40,000 (III). GGT-B was composed of two subunits with molecular weight of 22,000 (I) and 39,000 (II). The N-terminal amino acid sequences of GGT-A subunit I and GGT-B subunit I were very similar. GGT-A subunit II and GGT-B subunit II had an identical N-terminal amino acid sequence. That of GGT-A subunit III showed no similarity to the other subunits. Both GGTs had similar enzymatic properties (optimum pH and temperature: pH 8.8 and 55 degrees C) but showed a significantly different thermal stability at 55 degrees C. Both GGT-A and -B used D-gamma-glutamyl-p-nitroanilide as well as the L-isomer as the gamma-glutamyl donor and used various amino acids and peptides as the acceptor. It was also found that the PGA produced by the strain was hydrolyzed to glutamic acid by its own GGTs.
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PMID:Purification and properties of two isozymes of gamma-glutamyltranspeptidase from Bacillus subtilis TAM-4. 936 11

Bacillus licheniformis ATCC 9945a is one of the bacterial strains that produce gamma-poly(glutamic acid) (gamma-PGA). The use of carbohydrate medium components for gamma-PGA production was explored. Cells were grown in shake flasks or in controlled pH fermentors using medium formulations that contain different carbon sources. During the cultivations, aliquots were removed to monitor cell growth, carbon utilization, polymer production, and polymer molecular weight. Glucose was a better carbon source than glycerol for cell growth. Furthermore, glucose was utilized at a faster rate than glycerol, citrate, or glutamate. However, by using mixtures of glucose and glycerol in medium formulations, the efficiency of gamma-PGA production increased. For example, by increasing the glycerol in medium formulations from 0 to 40 g/L, the gamma-PGA broth concentration after 96 h increased from 5.7 to 20.5 g/L. Considering that glycerol utilization was low for the glucose/glycerol mixtures studied, it was unclear as to the mechanism by which glycerol leads to enhanced product formation. Cell growth and concomitant gamma-PGA production (12 g/L) at pH 6.5 was possible using glucose as a carbon source if trace amounts (0.5 g/L each) of citrate and glutamate were present in the medium. We suggested that citrate and glutamate were useful in preventing salt precipitation from the medium. In addition, glutamate may be preferred relative to ammonium chloride as a nitrogen source. The conversion of glucose to gamma-PGA by the strain ATCC 9945a was believed to occur by glycolysis of glucose to acetyl-CoA and tricarboxylic acid (TCA) cycle intermediates that were then metabolized via the TCA cycle to form alpha-ketoglutarate, which is a direct glutamate precursor.
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PMID:Effects of glucose and glycerol on gamma-poly(glutamic acid) formation by Bacillus licheniformis ATCC 9945a. 1009 19

The effect of the helical sense and the helical macrodipole moment of poly(glutamic acid) (PGA) amphiphiles on miscibility in their binary surface monolayers was examined by means of the surface pressure-area isotherm and spectroscopic measurements. Four types of PGA amphiphiles, having different chirality (l or d) and two long alkyl chains at the C- or N-terminus (1 or 2), were successfully prepared by polymerization of the corresponding NCAs. In acidic solutions, these amphiphiles were found to take right-handed or left-handed helical conformation, depending upon the chirality of the glutamic acid unit, and are dispersed in water molecularly without aggregation. On the other hand, the binary mixed monolayer of 1L and 1D provided a marked positive deviation from an ideal mixing curve, while that of the combination of 1L and 2L gave a much smaller negative deviation, suggesting that helical sense would play a more important role in monolayer miscibility. Copyright 1999 Academic Press.
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PMID:Effects of Helical Sense and Macrodipole on Helix Interaction in Poly(glutamic acid) Monolayers at the Air-Water Interface. 1060 53

In order to check the applicability of the broken-rodlike (BR) chain model, consisting of several rods alternatively joined by flexible random coils, to the conformational analysis of a polypeptide chain in the helix-to-coil transition regions, two relations predicted by the Zimm and Bragg theory and the method with the BR chain model are compared. It is shown that, despite a clear difference between the models employed in the two methods, they give substantially identical results in both probability P(j) that a helical residue is in a helical sequence j units long and averaged helical fraction dependence of the mean-squared radius of gyration. Thus the use of the method with the BR chain model in the conformational analysis of a polypeptide chain could be rationalized, at least, with the same degree of approximation as is assumed in the Zimm and Bragg theory. Using the scattering function for the BR chain model, averaged helical-sequence lengths are evaluated for partially ionized poly(L-glutamic acid) (PGA) in added-salt aqueous solution and nonionized PGA in N-methylacetamide, both in a helical state. As a result, it is shown that the length in the latter molecule is approximately tenfold longer than that in the former one.
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PMID:Applicability of broken-rodlike chain model to conformational analysis of polypeptide chain. 1079 81

A novel corrosion-resistant bioreactor composed of polyetherether ketone (PEEK), tech glass and silicium nitrite ceramics was constructed and applied for the cultivation of two newly isolated, extremely halophilic archaea producing poly(gamma-glutamic acid) (PGA), or poly(beta-hydroxy butyric acid) (PHB), respectively. These bacteria were isolated from hypersaline soil close to Aswan (Egypt). The isolate strain 40, which is related to the genus Natrialba, produced large amounts of PGA when cultivated on solid medium. Culture conditions were optimised applying the corrosion-resistant bioreactor. PGA production was dependent on NaCl concentration and occurred about at 20% (w/v) NaCl in the medium. A maximum cell density of about 1.6 g cell dry matter/l was obtained when the bioreactor was stirred and aerated in a batch fermentation process using proteose-peptone medium. The supernatant was monitored with respect to PGA formation, and after 90 h a maximum of 470 mg/l culture volume was detected by HPLC analysis. Culture conditions were optimized for the isolate 56, which accumulated PHB as intracellular granules. Batch fermentations in the stirred and aerated bioreactor applying acetate and n-butyric acid as carbon sources led to cell density of 2.28 g cell dry matter/l and a maximum PHB accumulation contributing to about 53% of cellular dry weight. About 4.6 g PHB were isolated from 10.6 g dried cells of strain 56, which exhibited a weight average molar mass of 2.3 x 10(5) g mol(-1) and a polydispersity of about 1.4.
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PMID:Polymer production by two newly isolated extremely halophilic archaea: application of a novel corrosion-resistant bioreactor. 1103 May 66

Glycopolypeptide (1) carrying the beta-D-Gal-(1-->3)-alpha-D-GalNAc unit as a kind model of asialo-type mucin was synthesized through three steps: enzymatic synthesis of p-nitrophenyl disaccharide glycoside, reduction of the p-nitrophenyl group, and coupling of the amino group with the carboxyl group of poly(L-glutamic acid)s (PGA). In a similar manner, glycopolypeptides (2-7) carrying beta-D-Gal-(1-->3)-beta-D-GalNAc, beta-D-Gal-(1-->3)-beta-D-GlcNAc, beta-D-Gal-(1-->6)-alpha-D-GalNAc, beta-D-Gal-(1-->6)-beta-D-GalNAc, alpha-D-GalNAc, and beta-D-GalNAc, respectively, were synthesized as analogous polymers of polymer 1. Glycopolypeptides 8 and 9 as a mimic of sialo-type mucin were further prepared from polymers 1 and 2 as the acceptor of CMP-Neu5Ac by alpha2,3-(O)-sialyltransferase, respectively. Interactions of these glycopolypeptides with lectins were investigated with the double-diffusion test and the hemagglutination-inhibition assay and in terms of an optical biosensor based on surface plasmon resonance. Polymers 1 and 2 reacted strongly with peanut (Arachis hypogaea) agglutinin (PNA) and Agaricus bisporus agglutinin (ABA). On the other hand, polymers 8 and 9 through sialylation from polymers 1 and 2 reacted with ABA, but did not with PNA. Other polymers 3-7 did not show any reactivity for both the lectins. These results show that PNA acts precisely in an exo manner on the beta-D-Gal-(1-->3)-D-GalNAc sequence, while ABA acts in an endo manner. Polymers 6 and 7 substituted with GalNAc reacted strongly with soybean (Glycine max) agglutinin and Vicia villosa agglutinin B4, regardless of the configuration of the glycosidic linkage. The interaction of all polymers with Bauhinia purpurea agglutinin was much stronger than that of the corresponding sugars. Polymers 8 and 9 reacted with wheat germ (Triticum vulgaris) agglutinin (WGA), to which Neu5Ac residues are needed for binding, but polymers 1 and 2 did not. These sugar-substituted glycopolypeptides interacted specifically with the corresponding lectins. Furthermore, polymers 4-7 reacted with WGA, but the corresponding sugars did not. It suggests that the N-acetyl group along the PGA backbone has a cluster effect for WGA. The artificial glycopolypeptides were shown to be useful as tools and probes of carbohydrate recognition and modeling in the analysis of glycoprotein-lectin interactions.
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PMID:Chemoenzymatic synthesis of glycopolypeptides carrying alpha-Neu5Ac-(2-->3)-beta-D-Gal-(1-->3)-alpha-D-GalNAc, beta-D-Gal-(1-->3)-alpha-D-GalNAc, and related compounds and analysis of their specific interactions with lectins. 1109 73

Poly(gamma-D-glutamic acid) (PGA)-producing strains of Bacillus species were investigated to determine their ability to contribute to reducing the amount of ammonium nitrogen in liquid manures and their ability to convert some of the ammonium into this polyamino acid as a transient depot for nitrogen. Organisms that do these things should help solve the serious environmental problems which are caused by the use of large amounts of liquid manure resulting from intensified agriculture; these problems are mainly due to the high content of ammonium nitrogen. Bacillus licheniformis ATCC 9945 and Bacillus subtilis were able to grow in liquid manure and to produce PGA in the presence of sodium gluconate. On artificial liquid manure these two strains were able to produce 0.85 and 0.79 g of PGA per liter, respectively. Under conditions that are found in intensified farming situations the ammonia content was reduced within 48 h from 1.3 to 0.75 g/liter. One mutant of B. subtilis 1551 impaired in the catabolism of PGA was obtained after nitrosoguanidine mutagenesis. This mutant produced PGA at a final concentration of 4.8 g/liter, whereas the wild type produced only 3.7 g/liter.
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PMID:Cultivation of bacteria producing polyamino acids with liquid manure as carbon and nitrogen source. 1115 24


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