Analysis of structure and function of gellans with different substitution patterns

Jay, A.J.; Colquhoun, Ian J.; Ridout, Michael J.; Brownsey, G.J.; Morris, Victor J.; Fialho, Arsénio M.; Leitão, Jorge H.; Sá‐Correia, Isabel

doi:10.1016/s0144-8617(97)00241-5

Cited by 62 publications

(39 citation statements)

References 32 publications

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“…The weight percentage of the polysaccharide and calcium ion in the hydrogels was selected according to literature [12,17,18] and to the results of several tests like the contact angle test, [3] performed in our laboratories on all samples to be treated. To prepare the hydrogel an aqueous solution of Gellan (20 g L…”

Section: Gel Preparationmentioning

confidence: 99%

“…Deacylated Gellan gum is obtained by alkali treatment of the native polysaccharide. Both native and deacetylated polymers form hydrogels [12][13][14][15][16][17][18] whose sol-gel transition process is temperature dependent [16,17]; in particular, the deacylated polysaccharide, in presence of calcium salts, forms hard and rigid hydrogel with a slow syneresis rate; moreover, it is homogenous, transparent, and stable to pH variations [14,18]. The pH stability assures that the hydrogel can be safety applied to every paper samples whatever its pH value.…”

Section: Introductionmentioning

confidence: 99%

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Gellan hydrogel as a powerful tool in paper cleaning process: A detailed study

Meisina

Micheli

Carbone

et al. 2014

Journal of Colloid and Interface Science

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Section: Gel Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gellan hydrogel as a powerful tool in paper cleaning process: A detailed study

Meisina

Micheli

Carbone

et al. 2014

Journal of Colloid and Interface Science

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“…In its native form, gellan is a linear anionic heteropolysaccharide based on a tetrasaccharide repeat unit composed of two molecules of D-glucose (D-Glc), one of D-glucuronic acid (D-GlcA), and one of L-rhamnose (LRha). Native gellan is partially esterified, with acetate and glycerate substituents on the D-glucosyl residue adjacent to the D-glucuronyl residue (1 mol of glycerate and 0.5 mol of acetate per repeat unit) (18), with an average molecular mass of about 0.5 MDa. The rheological properties of gellan are significantly modified upon the removal of acyl substituents.…”

mentioning

confidence: 99%

“…The rheological properties of gellan are significantly modified upon the removal of acyl substituents. They may be turned from soft and elastic gels to more brittle and harder ones, depending on the level of glycerate substituents present in the repeating unit (18).…”

mentioning

confidence: 99%

The Complex of Sphingomonas elodea ATCC 31461 Glucose-1-Phosphate Uridylyltransferase with Glucose-1-Phosphate Reveals a Novel Quaternary Structure, Unique among Nucleoside Diphosphate-Sugar Pyrophosphorylase Members

et al. 2007

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Gellan gum is a widely used commercial material, available in many different forms. Its economic importance has led to studies into the biosynthesis of exopolysaccharide gellan gum, which is industrially prepared in high yields using Sphingomonas elodea ATCC 31461. Glucose-1-phosphate uridylyltransferase mediates the reversible conversion of glucose-1-phosphate and UTP into UDP-glucose and pyrophosphate, which is a key step in the biosynthetic pathway of gellan gums. Here we present the X-ray crystal structure of the glucose-1-phosphate uridylyltransferase from S. elodea. The S. elodea enzyme shares strong monomeric similarity with glucose-1-phosphate thymidylyltransferase, several structures of which are known, although the quaternary structures of the active enzymes are rather different. A detailed comparison between S. elodea glucose-1-phosphate uridylyltransferase and available thymidylyltransferases is described and shows remarkable structural similarities, despite the low sequence identities between the two divergent groups of proteins.

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“…This EPS is composed of a repeating linear tetrasaccharide unit consisting of D-glucose (Glc), D-glucuronic acid (GlcA), and L-rhamnose (Rha) in a 2:1:1 ratio, respectively, with glycerate and acetate substituents (22). The significant changes in rheology observed upon the deacylation of gellan are essentially due to the glycerate substituents (17).…”

mentioning

confidence: 99%

Proteins Encoded bySphingomonas elodeaATCC 31461rmlAandugpGGenes, Involved in Gellan Gum Biosynthesis, Exhibit both dTDP- and UDP-Glucose Pyrophosphorylase Activities

Silva

Marques

Fialho

et al. 2005

Appl Environ Microbiol

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The commercial gelling agent gellan is a heteropolysaccharide produced by Sphingomonas elodea ATCC 31461. In this work, we carried out the biochemical characterization of the enzyme encoded by the first gene (rmlA) of the rml 4-gene cluster present in the 18-gene cluster required for gellan biosynthesis (gel cluster). Based on sequence homology, the putative rml operon is presumably involved in the biosynthesis of dTDPrhamnose, the sugar necessary for the incorporation of rhamnose in the gellan repeating unit. Heterologous RmlA was purified as a fused His 6 -RmlA protein from extracts prepared from Escherichia coli IPTG (isopropyl-␤-D-thiogalactopyranoside)-induced cells, and the protein was proven to exhibit dTDP-glucose pyrophosphorylase (K m of 12.0 M for dTDP-glucose) and UDP-glucose pyrophosphorylase (K m of 229.0 M for UDPglucose) activities in vitro. The N-terminal region of RmlA exhibits the motif G-X-G-T-R-X 2 -P-X-T, which is highly conserved among bacterial XDP-sugar pyrophosphorylases. The motif E-E-K-P, with the conserved lysine residue (K 163 ) predicted to be essential for glucose-1-phosphate binding, was observed. The S. elodea ATCC 31461 UgpG protein, encoded by the ugpG gene which maps outside the gel cluster, was previously identified as the UDP-glucose pyrophosphorylase involved in the formation of UDP-glucose, also required for gellan synthesis. In this study, we demonstrate that UgpG also exhibits dTDP-glucose pyrophosphorylase activity in vitro and compare the kinetic parameters of the two proteins for both substrates. DNA sequencing of ugpG gene-adjacent regions and sequence similarity studies suggest that this gene maps with others involved in the formation of sugar nucleotides presumably required for the biosynthesis of another cell polysaccharide(s).Sphingomonas elodea (formerly Pseudomonas elodea and also referred to as Sphingomonas paucimobilis) ATCC 31461 synthesizes the exopolysaccharide (EPS) gellan, a gelling agent with applications in the food, pharmaceutical, and other industries (13,41). This EPS is composed of a repeating linear tetrasaccharide unit consisting of D-glucose (Glc), D-glucuronic acid (GlcA), and L-rhamnose (Rha) in a 2:1:1 ratio, respectively, with glycerate and acetate substituents (22). The significant changes in rheology observed upon the deacylation of gellan are essentially due to the glycerate substituents (17).The gellan repeat unit is formed by sequential transfer of the sugar nucleotides to a membrane-anchored lipid carrier by committed glycosyltransferases, followed by gellan polymerization and export (34). The pathway leading to the formation of the sugar nucleotides UDP-Glc, UDP-GlcA, and dTDP-L-Rha, donors of the monomers for assembling the gellan tetrasaccharidic repeat unit, was elucidated (27, 34). Eighteen genes, organized in the gel cluster (15, 34) and coding for enzymes presumably involved in the synthesis of dTDP-L-Rha, glucosyltransferases, and proteins required for gellan polymerization and export, were identified. The organization and the...

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Analysis of structure and function of gellans with different substitution patterns

Cited by 62 publications

References 32 publications

Gellan hydrogel as a powerful tool in paper cleaning process: A detailed study

Gellan hydrogel as a powerful tool in paper cleaning process: A detailed study

The Complex of Sphingomonas elodea ATCC 31461 Glucose-1-Phosphate Uridylyltransferase with Glucose-1-Phosphate Reveals a Novel Quaternary Structure, Unique among Nucleoside Diphosphate-Sugar Pyrophosphorylase Members

Proteins Encoded bySphingomonas elodeaATCC 31461rmlAandugpGGenes, Involved in Gellan Gum Biosynthesis, Exhibit both dTDP- and UDP-Glucose Pyrophosphorylase Activities

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