Shunya Takahashi

Pheromone gland-specific fatty-acyl reductase of the silkmoth, Bombyx mori

The C10-C18 unsaturated, acyclic, aliphatic compounds that contain an oxygenated functional group (alcohol, aldehyde, or acetate ester) are a major class of sex pheromones produced by female moths. In the biosynthesis of these pheromone components, the key enzyme required to produce the oxygenated functional groups is fatty-acyl reductase (FAR). This enzyme converts fatty-acyl pheromone precursors to their corresponding alcohols, which, depending on the moth species, can then be acetylated or oxidized to the corresponding aldehydes. Despite the significant role this enzyme has in generating the species-specific oxygenated constituents of lepidopteran sex pheromones, the enzyme has yet to be fully characterized and identified. In experiments designed to characterize a pheromone-gland-specific FAR in the silkmoth, Bombyx mori, we have isolated a cDNA clone encoding a protein homologous to a FAR from the desert shrub, Simmondsia chinensis, commonly known as jojoba. The deduced amino acid sequence of this clone predicts a 460-aa protein with a consensus NAD(P)H binding motif within the amino terminus. Northern blot analysis indicated that 2-kb transcripts of this gene were specifically expressed in the pheromone gland at 1 day before adult eclosion. Functional expression of this gene in the yeast Saccharomyces cerevisiae not only confirmed the long-chain FAR activity, but also indicated a distinct substrate specificity. Finally, the transformed yeast cells evoked typical mating behavior in male moths when cultured with the pheromone precursor fatty acid, (E,Z)-10,12-hexadecadienoic acid.

Structural determination of sulfoquinovosyldiacylglycerol by chiral syntheses

Abstract Chiral sulfoquinovosyldiacylglycerols (SQDGs) have been synthesized to determine the absolute stereochemistry and the biological activities. The 1 H NMR spectrum of a natural SQDG is comparable to that of synthetic (2 S )-SQDG rather than that of the (2 R ) analogue. The biological activity of the respective isomers for DNA polymerase α and β inhibition was not distinguishable in the enzymatic assay.

Anti‐tumor Effect of Chemically Synthesized Sulfolipids Based on Sea Urchin's Natural Sulfonoquinovosylmonoacylglycerols

We recently reported that 3′‐sulfonoquinovosyl‐1′‐monoacylglycerol (designatedA‐5) extracted from sea urchin intestine was effective in suppressing the growth of solid tumors. Although the major fatty acid component of A‐5 was a saturated C16 acid, there were five other fatty acids, 14:0, 18:0, 14:1, 16:1, and 18:1, which constitute minor components of A‐5. Therefore, it remains unclear as to which of these six fatty acid components of A‐5 has the anti‐tumor effect. In this study, we synthesized sulfolipids each containing only one of these six fatty acids and tested their cytotoxicity against tumor cells and in vivo anti‐tumor effects on nude‐mice bearing solid tumors of human lung adenocarcinoma cell line A‐549. The IC50 values of all products against tumor cells were more than 10‐5M, suggesting weak cytotoxic activity compared with other chemotherapeutic compounds for cancer. On the other hand, in vivo anti‐tumor assay showed that sulfoquinovosyl‐monoacylglycerols (SQMG) composed of 14:1 and 18:1 (designated SQMG(14:1) and SQMG(18:1), respectively) were significantly effective in suppressing the growth of solid tumors. Our data suggested that these two SQMGs had a substantial anti‐tumor effect in vivo, and they are of interest as candidate drugs for anti‐cancer treatment.

Expeditious Synthesis of Vialinin B, an Extremely Potent Inhibitor of TNF-α Production

A first total synthesis of vialinin B, a powerful inhibitor (IC(50) 20 pM) of TNF-alpha production, is described. The key reactions include a double Suzuki-Miyaura coupling of electron-rich aryl bromide with a couple of phenylboronic acids, a Cu-mediated Ullmann reaction, and a LHMDS-promoted phenylacetylation. This synthesis proceeded in 11 steps with 18% overall yield from a known sesamol derivative.

An immunosuppressive effect by synthetic sulfonolipids deduced from sulfonoquinovosyl diacylglycerols of sea urchin.

Background. It is important to develop new immunosuppressive agents without clinical drawbacks. In this article, we reveal the possibility of a chemically synthetic sulfonolipid that acts as a novel immunosuppressive drug. Methods. We evaluated the immunosuppressive effect of 3-O-(6-deoxy-6-sulfono-&bgr;-D-glucopyranosyl)-1,2-di-O-acylglycerol (&bgr;-SQDG) that contains a saturated C18 fatty acid, which is designated as &bgr;-SQDG(18:0) by mixed lymphocyte reaction (MLR) and rat allogeneic skin graft. Then, we investigated the mechanism of immunosuppressive effect of &bgr;-SQDG(18:0). Results. &bgr;-SQDG(18:0) inhibited human MLR in a dose-dependent manner without overt cytotoxic effect and prolonged rat skin allograft rejection in vivo. &bgr;-SQDG(18:0) did not inhibit the direct activation of responder T. This reagent could not affect the expression of either major histocompatibility antigen complex (MHC) class I or class II molecules on the cell surface of the stimulator cells, antigen-presenting cells. In contrast, &bgr;-SQDG(18:0) was demonstrated to inhibit the binding among allogeneic lymphocytes. However, the expression of known cell surface accessory and adhesion molecules, such as CD4, CD28, leukocyte function-associated antigen 1, intercellular adhesion molecule 1, and CTLA-4, was not affected by &bgr;-SQDG(18:0) treatment. Conclusions. &bgr;-SQDG(18:0) might be a new class of the immunosuppressive reagent, and the inhibition of responder T-lymphocyte activation in MLR by &bgr;-SQDG(18:0) may be responsible for certain three-dimensional structures of this reagent or its quinovose binding to sulfonic acid.

Total synthesis of (-)-allosamidin, an insect chitinase inhibitor, employing chitin as a key starting material

Abstract (−)-Allosamidin ( 1 ), a novel insect chitinase inhibitor, was stereoselectively synthesized from di- and monosaccharidic constituens of chitin, N, N′-diacetylchitobiose ( 2 ) and D-glucosamine ( 3 ).

Vialinin A, a Novel 2,2-Diphenyl-1-picrylhydrazyl (DPPH) Radical Scavenger from an Edible Mushroom in China

While screening for bioactive compounds from edible mushrooms, a new potent antioxidant, vialinin A (1), together with a known compound, ganbajunin B (2), and a mixture of ganbajunins D (3) and E (4), were isolated from the dry fruiting bodies of Thelephora vialis. The structure of 1, 5′,6′-bis(phenylacetoxy)-1,1′:4′,1″-terphenyl-2′,3′,4,4″-tetraol, was elucidated by spectroscopic and chemical methods. This compound had strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging activity with an EC50 value of 14.0 μM, nearly equal to that of butylated hydroxytoluene (BHT; EC50=10.0 μM). A radical scavenging experiment using 1 and DPPH radicals indicated that 1 donated two hydrogen atoms to two molecules of the DPPH radical under hydrophobic conditions.

Total synthesis of pederin, a potent insect toxin: the efficient synthesis of the right half, (+)-benzoylpedamide

Abstract A simple and efficient synthesis of (+)-benzoylpedamide, the right half of pederin, was achieved in 16 steps with a 35% overall yield from ( S )-malic acid. The key steps include the SmI 2 -mediated intramolecular Reformatsky reaction, stereoselective allylation, the Sharpless asymmetric dihydroxylation, and amidation. The total synthesis of pederin was accomplished via coupling of the left and right halves.

Stereocontrolled synthesis of (−)-allosamizoline using D-glucosamine as a chiral template

Abstract (−)-Allosamizoline (1), a core component of novel insect chitinase inhibitor, allosamidin (2), was stereoselectively synthesized from D-glucosamine (3), using an efficient ring contraction reaction as a key step.

A novel DNA polymerase inhibitor and a potent apoptosis inducer: 2-mono-O-acyl-3-O-(α-d-sulfoquinovosyl)-glyceride with stearic acid

Sulfo-glycolipids in the class of sulfoquinovosyl diacylglycerol (SQDG) including the stereoisomers are potent inhibitors of DNA polymerase alpha and beta. However, since the alpha-configuration of SQDG with two stearic acids (alpha-SQDG-C(18)) can hardly penetrate cells, it has no cytotoxic effect. We tried and succeeded in making a permeable form, sulfoquinovosyl monoacylglycerol with a stearic acid (alpha-SQMG-C(18)) from alpha-SQDG-C(18) by hydrolysis with a pancreatic lipase. alpha-SQMG-C(18) inhibited DNA polymerase activity and was found to be a potent inhibitor of the growth of NUGC-3 cancer cells. alpha-SQMG-C(18) arrested the cell cycle at the G1 phase, and subsequently induced severe apoptosis. The arrest was correlated with an increased expression of p53 and cyclin E, indicating that alpha-SQMG-C(18) induced cell death through a p53-dependent apoptotic pathway.