Kimiko Ohtani

Possible immunodulating activities in an extract of edible brown alga, Hijikia fusiforme (Hijiki)

A significant immunomodulating activity was found in the hot-water-soluble extract of an edible brown seaweed, Hijikia fusiforme (Hijiki in Japanese) which showed an enhancing activity for the proliferative response of spleen cells in endotoxin-nonresponder C3H/HeJ mice. This activity was separated into polysaccharide and nonpolysaccharide fractions. The former fraction exhibited a much higher activity than that of the latter fraction. The enhancing effect of the polysaccharide fraction on the proliferative response of spleen cells was associated with the response of the B cell population, but not with that of the T cell population judged by experiments using nylon wool column-purified T cells and antisera against B cell- or T-cell-specific antigens. The active component of the polysaccharide fraction was further fractionated using DEAE cellulose column chromatography which also caused enhancing effects on polyclonal antibody (IgM and IgG) production and the release of interleukin-1α or tumour necrosis factor-α from peritoneal macrophages of C3H/HeJ mice. In addition, these immunomodulating activities of the polysaccharide fraction were associated with the polysaccharides themselves, but not with the artificial activities induced by contaminated endotoxins. The biochemical and physicochemical properties of the immunoenhancing polysaccharides were partially characterised and the significance of the present finding is discussed from the viewpoint of the immunopotentiating activity of edible seaweeds against carcinogenesis.

The structure of the glycan moiety of tora-bean (phaseolus vulgaris)lectin

Abstract The structure of the carbohydrate unit of Tora-bean lectin, which contains 7.8% of neutral carbohydrate, was elucidated by isolation of the glycopeptide from the digest by the action of proteolytic enzymes. The purified glycopeptide (mol. wt. 2,700) comprises 9.2 moles of d -mannose, 2.0 moles of 2-acetamido-2-deoxy- d -glucose, 0.6 mole of l -fucose, and 0.7 mole of d -xylose per mole of asparagine. Methylation analysis, Smith degradation and enzymic-degradation studies permitted formulation of a possible structure of the glycan of the glycopeptide, as follows.

The requirement of Zn2+ for the increase in ornithine decarboxylase induced by insulin and epidermal growth factor in primary cultured rat hepatocytes

Abstract The effect of restricted Zn 2+ on ornithine decarboxylase (ODC) was studied in primary cultured adult rat hepatocytes. ODC activity was increased 4 hr after adding insulin and epidermal growth factor. The maximal activity was maintained for 12 hr, it then decreased and returned to the control level by 24 hr. When the chelator, diethylenetriamine penta-acetic acid (DTPA) was added to insulin and epidermal growth factor, the enzyme activity was decreased by 50% and only the Zn 2+ of the bivalent metal ions tested was effective in reversing this effect. The level of the ODC messenger RNA did not change with addition of the chelator. The half-life of the ODC activity was decreased 2-fold by the chelator. Exposing the hepatocytes to DTPA reduced the incorporation of [ 3 H]thymidine into acid insoluble fraction. The inhibition of DNA synthesis was fully reversed by the addition of 600 μM Zn 2+ . These results suggest that a lack of Zn 2+ in hepatocytes impairs ODC activity mainly by destabilizing the enzyme resulting in the inhibition of DNA synthesis.

Effect of sucrose monostearate, an emulsifier, on polyamine metabolism and phosphatidylinositol turnover in Ehrlich ascites tumor cells

Sucrose esters of fatty acids have antitumor activity. We studied the effect of sucrose monostearate (SS), an emulsifier, on polyamine metabolism and phosphatidylinositol turnover in Ehrlich ascites tumor cells. The activity of ornithine decarboxylase (ODC) was increased in the cells by changing the medium. This increase in the activity was inhibited by adding sucrose stearate, but not sucrose or stearate to the medium. The activity of spermidine/spermine N1-acetyltransferase (SAT), a rate-limiting enzyme of polyamine biodegradation, was enhanced with the addition of SS in a time- and dose-dependent manner. The elevation of SAT activity was completely prevented when cycloheximide was added to the culture simultaneously. In in vitro studies, SS at various concentrations up to 1 mM hardly affected the activities of ODC or SAT. The incorporation of [3H]inositol into both fractions of inositolphospholipid and inositol phosphates was inhibited by SS. These results suggest that the perturbation of polyamine metabolism and phosphatidylinositol turnover is involved in the mechanism of antitumor activity of SS in Ehrlich ascites tumor cells.

Purification and Characterization of α-D-Mannosidase from the Seeds of Kaya, Torreya nucifera

Alpha-D-mannosidase was purified from the extract of seeds of Kaya, Torreya nucifera. The purified enzyme had a molecular mass of ˜ 3.6 × 105 daltons. This enzyme had an optimum pH at 4.5, and was stable at pH between 5.5 and 6.5. This enzyme appeared to be a metal enzyme containing Zn2+. The enzyme hydrolyzed p-nitrophenyl-α-D-mannoside, methyl-α-D-mannoside, α-1-»3-mannobiose, and α-1»6-mannobiose, with Km of 0.785 mM, 0.236 M, 2.505 mM, and 0.268 mM, respectively. The hydrolysis of various z-linked mannobioses indicated that the enzyme hydrolyzes the α-mannobioses in the order of α-(1→2)> -(1→6)> -(1→3).