NMR spectroscopic characterisation of oligosaccharides from two Ulva rigida ulvan samples (Ulvales, Chlorophyta) degraded by a lyase

Immunomodulating activities of acidic sulphated polysaccharides obtained from the seaweed Ulva rigida C. Agardh

Water-soluble acidic polysaccharides from the cell walls of Ulva rigida are mainly composed of disaccharides that contain glucuronic acid and sulphated rhamnose. The structure of disaccharides resembles that of glycosaminoglycans (GAGs) as they both contain glucuronic acid and sulphated sugars. Glycosaminoglycans occur in the extracellular matrix of animal connective tissues but can also be produced by leucocytes at inflammatory sites. Certain types of GAGs can even activate macrophages and therefore the acidic polysaccharides from U. rigida probably modulate macrophage activity. In the present study, we evaluated the effects of U. rigida polysaccharides on several RAW264.7 murine macrophage activities, including expression of inflammatory cytokines and receptors, nitric oxide and prostaglandin E2 (PGE(2)) production, and nitric oxide synthase 2 (NOS-2) and cyclooxygenase-2 (COX-2) gene expression. U. rigida acidic polysaccharides induced a more than two-fold increase in the expression of several chemokines (chemokine (C motif) ligand 1, chemokine (C-X-C motif) ligand 12, chemokine (C-C motif) ligand 22 and chemokine (C-X-C motif) ligand 14 (Cxcl14)) and in the expression of IL6 signal transducer and IL12 receptor beta 1. Incubation of macrophages with U. rigida polysaccharides also induced an increase in nitrite production, although this effect decreased considerably after desulphation of polysaccharides, suggesting that the sulphate group is important for the stimulatory capacity of these molecules. U. rigida polysaccharides also stimulated macrophage secretion of PGE(2) and induced an increase in COX-2 and NOS-2 expression. The results indicate that U. rigida acid polysaccharide can be used as an experimental immunostimulant for analysing inflammatory responses related to macrophage functions. In addition, these polysaccharides may also be of clinical interest for modifying certain macrophage activities in diseases where macrophage function is impaired or needs to be boosted.

Structure and Functional Properties of Ulvan, a Polysaccharide from Green Seaweeds

With today's interest in novel renewable chemicals and polymers, the underexploited marine green algae belonging to species of Ulva and Entermorpha stimulated interest as sources of polysaccharides with innovative structure and functional properties. These algae are common on all seashores and can produce in time an important amount of biomass in nutrient-enriched waters. The major water-soluble polysaccharide, ulvan, extracted from the cell wall represents about 8-29% of the algae dry weight. The original physicochemical, rheological, and biological properties recently unraveled for this complex sulfated aldobiouronan open the way for novel potential applications.

In vitro antioxidant activity of acetylated and benzoylated derivatives of polysaccharide extracted from Ulva pertusa (Chlorophyta)

The antioxidant activity of natural ulvan and its derivatives (acetylated and benzoylated ulvans) in vitro was determined, including scavenging activity against superoxide and hydroxyl radicals, reducing power, and chelating ability. Obvious differences in antioxidant activity between natural ulvan and its derivatives were observed, moreover, the antioxidant activity of acetylated and benzoylated ulvans was stronger than that of natural ulvan.

Purification and characterization of a novel glucuronan lyase from Trichoderma sp. GL2

The filamentous fungus Trichoderma sp. GL2 produces an extracellular glucuronan lyase (GL) when grown on glucuronan as the sole carbon source. In this paper, we report the purification to electrophoretical homogeneity of this polysaccharide lyase by size exclusion chromatography and anion exchange chromatography. The purified GL, classified as an endopolyglucuronate lyase, is a monomer with an apparent molecular weight of 27 kDa and an isoelectric point of 6.95. Despite an inhibition of the activity when polysaccharide substrates were substituted by acetates, the enzyme was active toward glucuronans (acetylated or not) and ulvan, leading to various (4,5)-unsaturated products as oligoglucuronans (acetylated or deacetylated), highly acetylated low-molecular-weight (LMW) glucuronans, and LMW ulvans.

Antioxidant activity of different sulfate content derivatives of polysaccharide extracted from Ulva pertusa (Chlorophyta) in vitro

Polysaccharide extracted from Ulva pertusa (Chlorophyta) is a group of sulfated heteropolysaccharide; for simplicity, the sulfated polysaccharide is referred to as ulvan in this paper. In this study, different sulfate content ulvans were prepared with sulfur trioxide/N,N-dimethylformamide (SO3-DMF) in formamide, and their antioxidant activities were investigated including scavenging activity of superoxide and hydroxyl radicals, reducing power and metal chelating ability. As expected, we obtained several satisfying results, as follows: firstly, high sulfate content ulvans had more effective scavenging activity on hydroxyl radical than natural ulvan. Secondly, comparing with natural ulvan, high sulfate content ulvans exhibited stronger reducing power. Thirdly, HU4 (sulfate content, 30.8%) and HU5 (sulfate content, 32.8%) showed more pronounce chelating ability on ferrous ion at high concentration than other samples.

Exopolygalacturonate lyase from Thermotoga maritima: cloning, characterization and organic synthesis application

A new exopolygalacturonate lyase (Pel) gene of the hyperthermophilic bacterium Thermotoga maritima was cloned and overexpressed in Escherichia coli cells. A 42 kDa monomeric Pel was shown to undergo N-terminal processing by cleavage at a putative site between alanine and serine residues. The enzyme catalyzes selectively a beta-4,5 elimination at the third galacturonic unit from the reducing end of polygalacturonic acid by producing (4-deoxy-alpha-L-threo-hex-4-enopyranosyluronic acid)-(1-->4)-(alpha-D-galactopyranosyluronic acid)-(1-->4)-alpha-D-galactopyranuronic acid (3) with a 60% yield. The optimum activity of the enzyme was detected at pH 9.5 and T> or=95 degrees C. The highly thermostable enzyme constitutes a useful catalyst for a simplified synthesis of 4,5-unsaturated trigalacturonic acid 3, a trisaccharide which is extremely difficult to obtain via chemical synthesis.