Search

Fucoidanases (EC 3.2.1.–) catalyze the hydrolysis of glycosidic bonds between fucose residues in fucoidans. Fucoidans are a compositionally and structurally diverse class of fucose‐containing sulfated polysaccharides that are primarily found in brown seaweeds. Here, the structural characterization of a novel endo‐α(1,4)‐fucoidanase, Mef1, from the marine bacterium Muricauda eckloniae is presented, showing sequence similarity to members of glycoside hydrolase family 107. Using carbohydrate polyacrylamide gel electrophoresis and nuclear magnetic resonance analyses, it is shown that the fucoidanase Mef1 catalyzes the cleavage of α(1,4)‐linkages between fucose residues sulfated on C2 in the structure [‐3)‐α‐l‐Fucp2S‐(1,4)‐α‐l‐Fucp2S‐(1‐]n in fucoidan from Fucus evanescens. Kinetic analysis of Mef1 activity by Fourier transform infrared spectroscopy revealed that the specific Mef1 fucoidanase activity (Uf) on F. evanescens fucoidan was 0.1 × 10−3 Uf µM−1. By crystal structure determination of Mef1 at 1.8 Å resolution, a single‐domain organization comprising a (β/α)8‐barrel domain was determined. The active site was in an extended, positively charged groove that is likely to be designed to accommodate the binding of the negatively charged, sulfated fucoidan substrate. The active site of Mef1 comprises the amino acids His270 and Asp187, providing acid/base and nucleophile groups, respectively, for the hydrolysis of glycosidic bonds in the fucoidan backbone. Electron densities were identified for two possible Ca2+ ions in the enzyme, one of which is partially exposed to the active‐site groove, while the other is very tightly coordinated. A water wire was discovered leading from the exterior of the Mef1 enzyme into the active site, passing the tightly coordinated Ca2+ site. [ABSTRACT FROM AUTHOR]

The need for a substitute for allograft and autograft is rising as bone graft surgeries exceed available supplies. We investigated the efficacy of the low‐molecular weight marine bioactive compound fucoidan (FUC) on bone regeneration and implant fixation in seven female sheep, as FUC has shown great promise as a bone substitute. Titanium implants were inserted bilaterally in the distal femurs to test three hydroxyapatite/fucoidan (HA/FUC) groups and compared to allograft. The HA was coated with either 500 or 1500 μg of FUC, obtained by microwave‐assisted chemical extraction, or 500 μg of FUC obtained by an enzyme‐assisted extraction method. The concentric 2‐mm gap around the implant was filled with either one of the HA/FUCs or allograft from the donor sheep. After 12 weeks, implant–bone blocks were harvested and divided into three parts for mechanical push‐out testing, immunohistochemistry, and micro‐CT and histomorphometry. Pronounced bone formations were observed by micro‐CT and histomorphometry in all groups, but higher bone volume fractions were seen in the allograft group compared to the three HA/FUC groups. The trabecular thickness, trabecular separation, and architectural anisotropy were all significantly higher in the allograft group compared to the three HA/FUC groups. In conclusion, adequate bone formation was observed in all groups, although the bone formation was significantly greater in the allograft group. Also, no significant differences existed in the shear mechanical properties between groups, suggesting that the combination of HA and FUC can achieve a similar fixation strength to allograft in this model. [ABSTRACT FROM AUTHOR]

Enriching foods with long‐chain n‐3 polyunsaturated fatty acids requires a delivery emulsion system, which is both thermodynamically and oxidatively stable. The antioxidant and stabilizing properties of three types of polysaccharide extracts from brown algae Saccharina latissima with a mixed composition of polysaccharides (SA: 98% sodium alginate, SF: 90% alginate and 9% fucoidan, SL: 14.5% fucoidan, 9.5% laminarin, and co‐extracted nonpolysaccharides) were evaluated. SA, SF, SL, and REF (added commercial sodium alginate) showed in vitro ferrous ion chelating ability in the order: SA (99%) > SL (78%) > REF (31%) > SF (16%). The difference in antioxidant activity between SA, REF, and SF appeared related to structural differences of alginate (M/G ratio). A storage trial was conducted using 70% (w/w) fish oil‐in‐water delivery emulsions added sodium caseinate (NaCas) (0.23 wt%) as emulsifier in combination with SA, SF, SL, or commercial NaAlg (REF) in different concentrations (C1 = 0.1, C2 = 0.2, C3 = 0.3, and C4 = 0.4 wt%). A control with only NaCas was included (CON). The physical (e.g., creaming and droplet‐size distribution) and oxidative (peroxide value and volatiles) stability of the emulsions, were evaluated (12 days, dark at 20˚C). Acceptable physical stability (creaming index) was found for REF (all concentrations), SF = 0.2 wt% (C2), SL and SA = 0.3 wt% (C3) and 0.4 wt% (C4). In general, the oxidative stability decreased by adding REF, SA, and SF (except for REF at C1), as prooxidant activity was observed. However, SA showed antioxidant activity against the formation of 2‐ethylfuran. SL showed antioxidant activity in decreasing the formation of volatile compounds in emulsions when added in concentrations above 0.2 wt%. [ABSTRACT FROM AUTHOR]