Showing papers by "Michio Murata published in 1994"

Affinity of okadaic acid to type-1 and type-2A protein phosphatases is markedly reduced by oxidation of its 27-hydroxyl group.

Abstract: Okadaic acid (OA), a potent inhibitor of type-1 and type-2A protein phosphatases (PP1 and PP2A), has four hydroxyl groups at 2, 7, 24 and 27 positions (see Figure 1). By chemical treatment of OA we synthesized a derivative, in which the 27-hydroxyl group was specifically oxidized (27-dehydro-OA). The inhibitory effect of this OA derivative was examined on the activities of PP1 and PP2A, which were inhibited by intact OA with dissociation constants (Ki) of 150 nM and 32 pM respectively. We found that the affinity of OA was decreased 40-fold (Ki = 6 microM) with PP1 and 230-fold (Ki = 7.3 nM) with PP2A after oxidation of the 27-hydroxyl group. According to the model of the three-dimensional conformation of OA on the basis of X-ray analyses, the 27-hydroxyl group appears to be present in a position relatively free from intramolecular bonding formation, in comparison with the other three hydroxyl groups. The marked increases in the Ki values for PP1 and PP2A, which indicate the reduction of the absolute values of the free energy of binding by 9 kJ/mol and 14 kJ/mol respectively, may imply that the 27-hydroxyl group serves as a binding site with the phosphatase molecules.

Fermentation broth and microorganisms which produce them

Abstract: The present invention relates to the compound A of the formula (A), the related compound B, carboxylic acid derived from acid anhydride group of these compounds and esters and salts thereof, microorganisms for producing the compounds, methods for producing the compounds A and/or B by using the microorganisms, and a treated or untreated fermentation broth obtained by culturing strains belonging to genus Zopfiella or Zopfiella curvata No. 37-3 strain. ##STR1## The present invention provides the compounds A and B, derivatives thereof, and treated or untreated fermentation broth obtained by culturing the strains belonging to genus Zopfiella or Zopfiella curvata No. 37-3 strain, which show an excellent activities as antifungal agent and anti-thrombotic agent.

Synthesis and Stereochemical Confirmation of the cis-Fused L/M and N/O Ring Systems of Maitotoxin.

Abstract: Stereocontrolled synthesis of cis-fused 1,6-dioxadecalin system 1, which corresponds to the L/M and N/O rings of maitotoxin, was accomplished. Comparison of its 1H and 13C NMR data with those of the natural toxin established the earlier stereochemical assignments.