title: Gene cloning and characterization of L-ribulose 3-epimerase from Mesorhizobium loti and its application to rare sugar production.
abstract: A gene encoding L-ribulose 3-epimerase (L-RE) from Mesorhizobium loti, an important enzyme for rare sugar production by the Izumoring strategy, was cloned and overexpressed. The enzyme showed highest activity toward L-ribulose (230 U/mg) among keto-pentoses and keto-hexoses. This is the first report on a ketose 3-epimerase showing highest activity toward keto-pentose. The optimum enzyme reaction conditions for L-RE were determined to be sodium phosphate buffer (pH 8.0) at 60 °C. The enzyme showed of higher maximum reaction a rate (416 U/mg) and catalytic efficiency (43 M(-1) min(-1)) for L-ribulose than other known ketose 3-epimerases. It was able to produce L-xylulose efficiently from ribitol in two-step reactions. In the end, 7.2 g of L-xylulose was obtained from 20 g of ribitol via L-ribulose at a yield of 36%.
authors.affiliation: Rare Sugar Research Center, Kagawa University, Miki, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Uechi
authors.forename: Goro
authors.initials: G
authors.lastname: Takata
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Fukai
authors.forename: Akihide
authors.initials: A
authors.lastname: Yoshihara
authors.forename: Kenji
authors.initials: K
authors.lastname: Morimoto
mesh_terms: D000595:Amino Acid Sequence; D002238:Carbohydrate Epimerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004795:Enzyme Stability / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D059128:Mesorhizobium / Q000201:enzymology* / Q000235:genetics*; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D010429:Pentoses / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012255:Ribitol / Q000737:chemistry; D017421:Sequence Analysis; D013379:Substrate Specificity; D013696:Temperature; D014996:Xylulose / Q000737:chemistry*
chemical_list: D008670:Metals; D010429:Pentoses; D011994:Recombinant Proteins; D012255:Ribitol; C100182:ribulose; D014996:Xylulose; D002238:Carbohydrate Epimerases