title: D-xylose isomerase from a marine bacterium, Vibrio sp. strain XY-214, and D-xylulose production from β-1,3-xylan.
abstract: The xylA gene from a marine bacterium, Vibrio sp. strain XY-214, encoding D-xylose isomerase (XylA) was cloned and expressed in Escherichia coli. The xylA gene consisted of 1,320-bp nucleotides encoding a protein of 439 amino acids with a predicted molecular weight of 49,264. XylA was classified into group II xylose isomerases. The native XylA was estimated to be a homotetramer with a molecular mass of 190 kDa. The purified recombinant XylA exhibited maximal activity at 60°C and pH 7.5. Its apparent K (m) values for D-xylose and D-glucose were 7.93 and 187 mM, respectively. Furthermore, we carried out D-xylulose production from β-1,3-xylan, a major cell wall polysaccharide component of the killer alga Caulerpa taxifolia. The synergistic action of β-1,3-xylanase (TxyA) and β-1,3-xylosidase (XloA) from Vibrio sp. strain XY-214 enabled efficient saccharification of β-1,3-xylan to D-xylose. D-xylose was then converted to D-xylulose by using XylA from the strain XY-214. The conversion rate of D-xylose to D-xylulose by XylA was found to be approximately 40% in the presence of 4 mM sodium tetraborate after 2 h of incubation. These results demonstrated that TxyA, XloA, and XylA from Vibrio sp. strain XY-214 are useful tools for D-xylulose production from β-1,3-xylan. Because D-xylulose can be used as a source for ethanol fermentation by yeast Saccharomyces cerevisiae, the present study will provide a basis for ethanol production from β-1,3-xylan.
authors.affiliation: Laboratory for the Utilization of Aquatic Bioresources, Department of Life Science, Graduate School of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Umemoto
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shibata
authors.forename: Toshiyoshi
authors.initials: T
authors.lastname: Araki
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007535:Isomerases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D013696:Temperature; D014733:Vibrio / Q000145:classification* / Q000201:enzymology*; D014990:Xylans / Q000378:metabolism*; D014994:Xylose / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D014990:Xylans; C065917:1,3-xylan; D014994:Xylose; D007535:Isomerases