Irina Y. Bakunina

Structure, biological activity, and enzymatic transformation of fucoidans from the brown seaweeds.

Recent advances in the study of fucoidans, biologically active sulfated α‐L‐fucans of diverse structures and synthesized exclusively by marine organisms, are overviewed. Their structure, biological activity, the products of their enzymatic degradation and the different enzymes of degradation and modification are considered.

A new precursor for the immobilization of enzymes inside sol-gel-derived hybrid silica nanocomposites containing polysaccharides

Tetrakis(2-hydroxyethyl) orthosilicate (THEOS) introduced by Hoffmann et al. (J. Phys. Chem. B., 106 (2002) 1528) was first used to prepare hybrid nanocomposites containing various polysaccharides and immobilize enzymes in these materials. Two different types of O-glycoside hydrolyses (EC3.2.1), 1-->3-beta-D-glucanase LIV from marine mollusk Spisula sacchalinensis and alpha-D-galactosidase from marine bacterium Pseudoalteromonas sp. KMM 701, were taken for the immobilization. To reveal whether the polysaccharide inside the hybrid material influences the enzyme entrapment and functioning, negatively charged xanthan, cationic derivative of hydroxyethylcellulose and uncharged locust bean gum were examined. The mechanical properties of these nanocomposites were characterized by a dynamic rheology and their structure by a scanning electron microscopy. It was found that 1-->3-beta-D-glucanase was usually immobilized without the loss of its activity, while the alpha-D-galactosidase activity in the immobilized state depended on the polysaccharide type of material. An important point is that the amount of immobilized enzymes was small, comparable to their content in the living cells. It was shown by the scanning electron microscopy that the hybrid nanocomposites are sufficiently porous that allows the enzymatic substrates and products to diffuse from an external aqueous solution to the enzymes, whereas protein molecules were immobilized firmly and not easily washed out of the silica matrix. A sharp increase of the enzyme lifetime (more than a hundred times) was observed after the immobilization. As established, the efficient entrapment of enzymes is caused by few advantages of new precursor over the currently used TEOS and TMOS: (i) organic solvents and catalysts are not needed owing to the complete solubility of THEOS in water and the catalytic effect of polysaccharides on the sol-gel processes; (ii) the entrapment of enzymes can be performed at any pH which is suitable for their structural integrity and functionality; (iii) a gel can be prepared at reduced concentrations of THEOS (1-2%) in the initial solution that excludes a notable heat release in the course of its hydrolysis.

Ecophysiological variabilities in Ectohydrolytic enzyme activities of some Pseudoalteromonas species, P. citrea, P. issachenkonii, and P. nigrifaciens

The ecophysiological variabilities in the ectohydrolytic enzyme profiles of the three species of Pseudoalteromonas, P. citrea, P. issachenkonii, and P. nigrifaciens, have been investigated. Forty-one bacteria isolated from several invertebrates, macroalgae, sea grass, and the surrounding water exhibited different patterns of hydrolytic enzyme activities measured as the hydrolysis of either native biopolymers or fluorogenic substrates. The activities of the following enzymes were assayed: proteinase, tyrosinase, lipase, amylase, chitinase, agarase, fucoidan hydrolase, laminaranase, alginase, pustulanase, cellulase, β-glucosidase, α- and β-galactosidases, β-N-acetylglucosaminidase, β-glucosaminidase, β-xylosidase, and α-mannosidase. The occurrence and cell-specific activities of all enzymes varied over a broad range (from 0 to 44 μmol EU per hour) and depended not only on taxonomic affiliation of the strain, but also on the source/place of its isolation. This suggests ‘specialization’ of different species for different types of polymeric substrates as, for example, all strains of P. citrea and P. issachenkonii hydrolyzed alginate and laminaran, while strains of P. nigrifaciens were lacking the ability to hydrolyze most of the algal polysaccharides. The incidence of certain enzymes such as fucoidan hydrolases, alginate lyases, agarases, and α-galactosidases might be strain specific and reflect its particular ecological habitat.

An endo-(1→3)-β-d-glucanase from the scallop Chlamys albidus: catalytic properties, cDNA cloning and secondary-structure characterization

An endo-(1-->3)-beta-d-glucanase (L(0)) with molecular mass of 37 kDa was purified to homogeneity from the crystalline style of the scallop Chlamys albidus. The endo-(1-->3)-beta-d-glucanase was extremely thermolabile with a half-life of 10 min at 37 degrees C. L(0) hydrolyzed laminaran with K(m) approximately 0.75 mg/mL, and catalyzed effectively transglycosylation reactions with laminaran as donor and p-nitrophenyl betad-glucoside as acceptor (K(m) approximately 2mg/mL for laminaran) and laminaran as donor and as acceptor (K(m) approximately 5mg/mL) yielding p-nitrophenyl betad-glucooligosaccharides (n=2-6) and high-molecular branching (1-->3),(1-->6)-beta-d-glucans, respectively. Efficiency of hydrolysis and transglycosylation processes depended on the substrate structure and decreased appreciably with the increase of the percentage of beta-(1-->6)-glycosidic bonds, and laminaran with 10% of beta-(1-->6)-glycosidic bonds was the optimal substrate for both reactions. The CD spectrum of L(0) was characteristic for a protein with prevailing beta secondary-structural elements. Binding L(0) with d-glucose as the best acceptor for transglycosylation was investigated by the methods of intrinsic tryptophan fluorescence and CD. Glucose in concentration sufficient to saturate the enzyme binding sites resulted in a red shift in the maximum of fluorescence emission of 1-1.5 nm and quenching the Trp fluorescence up to 50%. An apparent association constant of L(0) with glucose (K(a)=7.4 x 10(5)+/-1.1 x 10(5)M(-1)) and stoichiometry (n=13.3+/-0.7) was calculated. The cDNA encoding L(0) was sequenced, and the enzyme was classified in glycoside hydrolases family 16 on the basis of the amino acid sequence similarity.

Optimization of glycosidases production by Pseudoalteromonas issachenkonii KMM 3549T

Aims: The present work aimed to design an optimized medium to yield a higher production of glycosides by Pseudoalteromonas issachenkonii KMM 3549T. 
Methods and Results: Higher levels of fucoidan hydrolase, alginase, laminaranase and b‐N‐acetylglucosaminidase production were obtained with peptone concentrations ranging from 2·5 g l−1 to 10 g l−1, while the presence of both yeast extract and glucose did not affect enzyme production. The activity of fucoidan hydrolase and laminaranase increased up to 4·83 µM h−1 mg−1 and 19·23 µM h−1 mg−1 protein, respectively, in growth media containing xylose (1·0 g l−1), laminarin (0·5 g l−1) or alginate (0·5 g l−1), and production of b‐N‐acetylglucosaminidase substantially increased in the presence of fucoidan (0·5 g l−1) or galactose (1 g l−1). All polysaccharides tested in concentrations of 0·5 g l−1 fucoidan and 0·2 g l−1 fucose induced production of alginase (up to 5·06 µM h−1 mg−1 protein). 
Conclusions: The production of glycosidases is not only stimulated by the presence of algal polysaccharides, but may also be stimulated by monosaccharides (e.g. xylose). 
Significance and Impact of the Study: The production of glycosidases by Pseudoalteromonas issachenkonii KMM 3549T was significantly improved by using a simple nutrient medium containing peptone (2·5 g l−1) and xylose (5·0 g l−1) in 100% natural seawater.

Molecular Characterization and Therapeutic Potential of a Marine Bacterium Pseudoalteromonas sp. KMM 701 α-Galactosidase

An α-galactosidase capable of converting B red blood cells into the universal blood type cells at the neutral pH was produced by a novel obligate marine bacterium strain KMM 701 (VKM B-2135 D). The organism is heterotrophic, aerobic, and halophilic and requires Na+ ions and temperature up to 34°C for its growth. The strain has a unique combination of polysaccharide-degrading enzymes. Its single intracellular α-galactosidase exceeded other glycoside hydrolases in the level of expression up to 20-fold. The α-galactosidase was purified to determine the N-terminal amino acid sequences and new activities. It was found to inhibit Corynebacterium diphtheria adhesion to host buccal epithelium cell surfaces with high effectiveness. The nucleotide sequence of the homodimeric α-galactosidase indicates that its subunit is composed of 710 amino acid residues with a calculated Mr of 80,055. This α-galactosidase shares structural property with 36 family glycoside hydrolases. The properties of the enzyme are likely to be highly beneficial for medicinal purposes.

Comparative analysis of glycoside hydrolases activities from phylogenetically diverse marine bacteria of the genus Arenibacter.

A total of 16 marine strains belonging to the genus Arenibacter, recovered from diverse microbial communities associated with various marine habitats and collected from different locations, were evaluated in degradation of natural polysaccharides and chromogenic glycosides. Most strains were affiliated with five recognized species, and some presented three new species within the genus Arenibacter. No strains contained enzymes depolymerizing polysaccharides, but synthesized a wide spectrum of glycosidases. Highly active β-N-acetylglucosaminidases and α-N-acetylgalactosaminidases were the main glycosidases for all Arenibacter. The genes, encoding two new members of glycoside hydrolyses (GH) families, 20 and 109, were isolated and characterized from the genomes of Arenibacter latericius. Molecular genetic analysis using glycosidase-specific primers shows the absence of GH27 and GH36 genes. A sequence comparison with functionally-characterized GH20 and GH109 enzymes shows that both sequences are closest to the enzymes of chitinolytic bacteria Vibrio furnissii and Cellulomonas fimi of marine and terrestrial origin, as well as human pathogen Elisabethkingia meningoseptica and simbionts Akkermansia muciniphila, gut and non-gut Bacteroides, respectively. These results revealed that the genus Arenibacter is a highly taxonomic diverse group of microorganisms, which can participate in degradation of natural polymers in marine environments depending on their niche and habitat adaptations. They are new prospective candidates for biotechnological applications due to their production of unique glycosidases.

Hooked on α-d-galactosidases: from biomedicine to enzymatic synthesis

Abstract α-d-Galactosidases (EC 3.2.1.22) are enzymes employed in a number of useful bio-based applications. We have depicted a comprehensive general survey of α-d-galactosidases from different origin with special emphasis on marine example(s). The structures of natural α-galactosyl containing compounds are described. In addition to 3D structures and mechanisms of action of α-d-galactosidases, different sources, natural function and genetic regulation are also covered. Finally, hydrolytic and synthetic exploitations as free or immobilized biocatalysts are reviewed. Interest in the synthetic aspects during the next years is anticipated for access to important small molecules by green technology with an emphasis on alternative selectivity of this class of enzymes from different sources.

Stereochemical course of hydrolytic reaction catalyzed by alpha-galactosidase from cold adaptable marine bacterium of genus Pseudoalteromonas

The recombinant α-galactosidase of the marine bacterium (α-PsGal) was synthesized with the use of the plasmid 40Gal, consisting of plasmid pET-40b (+) (Novagen) and the gene corresponding to the open reading frame of the mature α-galactosidase of marine bacterium Pseudoalteromonas sp. KMM 701, transformed into the Escherichia coli Rosetta(DE3) cells. In order to understand the mechanism of action, the stereochemistry of hydrolysis of 4-nitrophenyl α-D-galactopyranoside (4-NPGP) by α-PsGal was measured by 1H NMR spectroscopy. The kinetics of formation of α- and β-anomer of galactose showed that α-anomer initially formed and accumulated, and then an appreciable amount of β-anomer appeared as a result of mutarotation. The data clearly show that the enzymatic hydrolysis of 4-NPGP proceeds with the retention of anomeric configuration, probably, due to a double displacement mechanism of reaction.

Polaribacter staleyi sp. nov., a polysaccharide-degrading marine bacterium isolated from the red alga Ahnfeltia tobuchiensis

A Gram-stain-negative, rod-shaped, motile by gliding and yellow-pigmented bacterium, designated strain 10Alg 139T, was isolated from the Pacific red alga Ahnfeltiato buchiensis. The phylogenetic analysis based on 16S rRNA gene sequences showed that the novel strain belonged to the genus Polaribacter, a member of the family Flavobacteriaceae, the phylum Bacteroidetes, with highest sequence similarity to Polaribacter butkevichii KMM 3938T (99.3 %) and 93.3-98.6 % to other recognized Polaribacter species. The prevalent fatty acids of strain 10Alg 139T were iso-C15 : 0 3-OH, C15 : 0 3-OH, iso-C15:0, iso-C13 : 0, C15 : 0 and C15 : 1ω6c. The polar lipid profile consisted of the major lipids phosphatidylethanolamine, two unidentified aminolipids and four unidentified lipids. The main respiratory quinone was menaquinone 6. The DNA G+C content of the type strain is 31.8 mol%. The new isolate and the type strains of recognized species of the genus Polaribacter were readily distinguished based on a number of phenotypic characteristics. A combination of the genotypic and phenotypic data showed that the isolate from alga represents a novel species of the genus Polaribacter, for which the name Polaribacterstaleyi sp. nov. is proposed. The type strain is 10Alg 139T (=KCTC 52773T=KMM 6729T).