Shuichi Seto

Proton magnetic resonance spectra of D-gluco-oligosaccharides and D-glucans

Abstract The p.m.r. spectra of some D -gluco-oligosaccharides and D -glucans in deuterium oxide were studied with respect to the anomeric proton. In (1→2)-linked glucobioses, the effect of change in configuration of the hydroxyl group at C-1 on the chemical shifts of the glycosidic proton is noted. Equilibrium mixtures of (1→2)-linked glucobioses contained more α-anomer than did the other examples, despite the cis configuration of substituents at C-1 and C-2. Some D -glucans were investigated with regard to the degree of branching, although solubility was a limitation.

13 C nuclear magnetic resonance spectra of glucobioses, glucotrioses, and glucans

Natural-abundance carbon-13 n.m.r. spectra of all the glucobioses and of four selected glucotrioses in aqueous solution have been measured and are discussed. Peak assignments were made on the basis of comparison with the spectra of methyl glucopyranosides, four mono-O-methylglucoses and five methyl glucobiosides. Carbon-13 n.m.r. spectroscopy proved to be a useful tool for stereochemical characterisation of these oligosaccharides. In addition, carbon-13 n.m.r. spectra of the β-limit dextrins from glycogen and amylopectin have been measured and the differences between them are discussed.

Formation of polyprenyl phosphates by a cell-free enzyme of Micrococcus lysodeikticus.

Abstract A cell-free enzyme of Micrococcus lysodeikticus catalyzed the formation of polyprenyl phosphates ranging in carbon chain from C-20 to C-55 with a predominance of C-40. Homogenates of rabbit liver (or kidney) and yeast catalyzed effectively the hydrolysis of these long chain prenyl phosphates but did not act on the pyrophosphate esters.

Variable product specificity of solanesyl pyrophosphate synthetase

Abstract The distribution of polyprenyl pyrophosphates synthesized by the action of solanesyl pyrophosphate synthetase from Micrococcus luteus is dramatically changed depending on the Mg++ concentration. When the metal ion concentration is higher than 5 mM, octaprenyl and solanesyl (nonaprenyl) pyrophosphate are synthesized predominantly. On the other hand, when the metal ion level is lower than 0.5 mM, a variety of polyprenyl pyrophosphates ranging in carbon chain length from C15 to C40 are formed. Heptaprenyl pyrophosphate is the longest of the products formed at 0.1 mM of Mg++.

New butenolides from Aspergillus terreus

Abstract From the culture filtrate of Aspergillus terreus , seven related yellow substances were isolated and the simplest, C 17 H 12 O 5 , was proved to be 3-( p -hydroxyphenyl)-4-hydroxy-5-( p -hydroxybenzylidene)-2(5H)-furanone.

[19] Prenyltransferases of pumpkin fruit

Publisher Summary This chapter focuses on preparation of prenyltransferases of pumpkin fruit. It discusses assay methods in which principle and procedure are described. The assay method determines the amount of 14 C labeled isopentenyl pyrophosphate, which reacts with allylic substrates to form 14 C-labeled compounds which, after acid treatment, are extractable with hexane. In the assay of crude preparations, it is recommended to use geranyl pyrophosphate plus [ 14 C]isopentenyl pyrophosphate in the presence of Mn 2+ and farnesyl pyrophosphate plus [ 14 C]isopentenyl pyrophosphate in the presence of Mn 2+ for the assay of farnesylpyrophosphate synthetase and geranylgeranylpyrophosphate synthetase, respectively. The product of the farnesylpyrophosphate synthetase reaction starting with dimethylallyl pyrophosphate and isopentenyl pyrophosphate is a mixture of geranyl pyrophosphate and all-trans-farnesylpyrophosphate, whereas all-trans-geranylgeranyl pyrophosphate is the only product in the reaction catalyzed by geranylgeranylpyrophosphate synthetase regardless of the chain length of the allylicsubstrate with which the reaction is initiated. Purification of enzymes is also discussed in the chapter in which extraction and fractionation are described.

Comparative specificity of prenyltransferase of pig liver and pumpkin with respect to artificial substrates.

Abstract Comparative studies on the substrate specificity of prenyltransferase (dimethylallyl pyrophosphate:isopentenyl pyrophosphate dimethylallyltransferase, EC 2.5.1.1) from pig liver and from pumpkin showed that the enzyme from liver had broader specificity with respect to artificial substrates than the enzyme from pumpkin. Seven allylic pyrophosphates, which were inactive as substrates for pumpkin enzyme, were found to be active for liver enzyme. These were cis -3-methyl-2-octenyl, trans -3,4-dimethyl-2-pentenyl, trans -3,4-dimethyl-2-hexenyl, trans -3,5-dimethyl-2-hexenyl, trans -3,6-dimethyl-2-heptenyl, 3-propyl-2-hexenyl and cycloheptylideneethyl pyrophosphates. No difference was observed between the two enzymes, in that geranyl pyrophosphate or its homolog was accumulated in an early stage of the reaction of dimethylallyl pyrophosphate or its homolog with isopentenyl pyrophosphate.

A new prenyltransferase from Micrococcus lysodeikticus.

Abstract A new prenyltransferase which catalyzes the synthesis of geranyl pyrophosphate as the only product from dimethylallyl pyrophosphate and isopentenyl pyrophosphate has been separated from other known prenyltransferases from Micrococcus lysodeikticus . This enzyme fraction is also capable of synthesizing all- trans geranylgeranyl pyrophosphate from farnesyl pyrophosphate and isopentenyl pyrophosphate though it lacks ability to synthesize farnesyl pyrophosphate.

Structures of pulvinone derivatives from Aspergillus terreus

Abstract The structures were established of six pulvinone derivatives, together with 3-(p-hydroxyphenyl)-4-hydroxy-5-(p-hydroxybenzylidene)-2(5H)-furanone (dihydroxy pulvinone), which were all isolated from a culture of Aspergillus terreus. Dihydroxy pulvinone is the fundamental structure for the six new compounds, which have one more hydroxyl group and/or two 3,3-dimethylallyll or related groups substituted on the aryl nuclei.

Two isopentenyl pyrophosphate isomerases from pumpkin fruit

Abstract Two isopentenyl pyrophosphate isomerase fractions were separated by hydroxylapatite chromatography of pumpkin fruit extract.