Masaakira Maeda

Inhibition of thrombin by sulfated polysaccharides isolated from green algae.

Eight different sulfated polysaccharides were isolated from Chlorophyta. All exhibited thrombin inhibition through a heparin cofactor II (HCII)-dependent pathway, and their effects on the inhibition of thrombin were more potent than those of heparin or dermatan sulfate. In particular, remarkably potent thrombin inhibition was found for the sulfated polysaccharides isolated from the Codiales. In the presence of these sulfated polysaccharides, both the recombinant HCII (rHCII) variants Lys(173)-->Leu and Arg(189)-->His, which are defective in interactions with heparin and dermatan sulfate, respectively, inhibited thrombin in a manner similar to native rHCII. This result indicates that the binding site of HCII for each of these eight sulfated polysaccharides is different from the heparin- or dermatan sulfate-binding site. All the sulfated polysaccharides but RS-2 significantly stimulated the inhibition of thrombin by an N-terminal deletion mutant of HCII (rHCII-Delta74). Furthermore, hirudin(54-65) decreased only 2-5-fold the rate of thrombin inhibition by HCII stimulated by the sulfated polysaccharides, while HD22, a single-stranded DNA aptamer that binds exosite II of thrombin, produced an approximately 10-fold reduction in this rate. These results suggest that, unlike heparin and dermatan sulfate, the sulfated polysaccharides isolated from Chlorophyta activate HCII primarily by an allosteric mechanism different from displacement and template mechanisms.

Heparinoid-active sulphated polysaccharides from Monostroma nitidum and their distribution in the Chlorophyta

Abstract Blood anticoagulant activity, especially antithrombin time, was examined with hot water extracts containing seaweed polysaccharides from 23 dilterent species of the Chlorophyta. No correlation between this activity and the systematic positions of the species was found. A remarkably high activity was found in extracts fromMonostroma nitidum, and the active polysaccharide was purified by chromatography to yield aca six-fold higher activity than that of standard heparin. The active material obtained was a high rhamnose-containing sulphated polysaccharide.

Rhamnan sulfate from cell walls of Monostroma latissimum

Abstract Rhamnan sulfate from cell walls of Monostroma latissimum was purified through subsequent chromatographic systems. The purified polysaccharide consisted of large amounts of rhamnose residues and appeared to be an entire homopolysaccharide. Antithrombin activity was lower than rhamnan sulfate previously obtained from M. nitidum but similar to standard heparin. Studies of the major structural parts of the rhamnan sulfate by periodate oxidation, Smith degradation and permethylation, showed it to consist of 1,3- and 1,2-linked rhamnose residues in a ratio of 3 : 2. Sulfate was mainly substituted at C-3 or C-4 in the 1,2-linked rhamnose residue. The detection of oligosaccharides by matrix-assisted laser desorption\ionization time-of-flight mass spectrometry supports this structure. These results suggested that rhamnan sulfate from the Monostromaceae has quite different structural properties from ulvan from the Ulvaceae.

Studies on the cell-wall mannan of the siphonous green algae, Codium latum

Abstract Cell-wall mannan from Codium latum was completely solubilized as methylol mannan from their microfibrils by treatment with paraformaldehyde-Me 2 SO system at 150 °C, and it was purified by gel-permeation chromatography with Toyopearl gel under Me 2 SO elution. Mannan was regenerated by dilution of the purified methylol mannan with water or methanol. The elution profile of regenerated mannan on gel permeation chromatography under Me 2 SO or the IR spectrum of the deuterium-exchanged, fractionated mannan revealed that the cell-wall mannan was aggregated as higher molecular weight material through intermolecular hydrogen bonding to form a difficulty soluble material. The results of structural determination on the purified mannan, including periodate oxidation and permethylation analysis, revealed a (1 → 4)-β-linked linear polysaccharide, as well as other cell-wall microfibril polysaccharides.

Cellulose in the cell wall of the siphonous green alga, Bryopsis maxima

Abstract The cell wall microfibrils of Bryopsis maxima , a member of the order Siphonales which have been referred to as “noncellulosic plants”, contain d -glucan and >90% of (1→3)-β- d -xylan. A combination of enzymic analysis and 1 H-n.m.r. spectroscopy confirmed that the d -glucan was cellulose and that the algal cell-wall microfibril seems to be composed not of a d -gluco- d -xylan but mainly of a (1→3)-β- d -xylan with small proportions of cellulose, which seemed to be present in an amorphous state in contrast to the trihelical strands of the (1→3)-β- d -xylan.

Cell wall polysaccharides of Pseudodichotomosiphon constrictus with special reference to its systematics

Abstract The major cell wall polysaccharide was isolated from the fibrous materials of Pseudodichotomosiphon constrictus. Structural determination by chemical and enzymatic procedures, established that it was not xylan, which is characteristic of the Siphonales, but cellulose as previously identified in Vaucheria. This character, as well as results from pigment analysis, the fine structures of the chloroplast or motile cells demonstrated that the genus has more affinity to the Xanthosophyceae than Siphonales in the Chlorophyta.

Detection of rutin by high-performance liquid chromatography and its application to taxonomic studies ofCalamagrostis (Poaceae)

A rapid and reproducible microanalysis technique for detecting rutin was established using reversed phase high-performance liquid chromatography. The usefulness of its application to studies in complicated internal structures of some species or species complexes ofCalamagrostis was discussed.