title: Characterization of a mutant glucose isomerase from Thermoanaerobacterium saccharolyticum.
abstract: A series of site-directed mutant glucose isomerase at tryptophan 139 from Thermoanaerobacterium saccharolyticum strain B6A were purified to gel electrophoretic homogeneity, and the biochemical properties were determined. W139F mutation is the most efficient mutant derivative with a tenfold increase in its catalytic efficiency toward glucose compared with the native GI. With a maximal activity at 80 °C of 59.58 U/mg on glucose, this mutant derivative is the most active type ever reported. The enzyme activity was maximal at 90 °C and like other glucose isomerase, this mutant enzyme required Co(2+) or Mg(2+) for enzyme activity and thermal stability (stable for 20 h at 80 °C in the absence of substrate). Its optimum pH was around 7.0, and it had 86 % of its maximum activity at pH 6.0 incubated for 12 h at 60 °C. This enzyme was determined as thermostable and weak-acid stable. These findings indicated that the mutant GI W139F from T. saccharolyticum strain B6A is appropriate for use as a potential candidate for high-fructose corn syrup producing enzyme.
authors.affiliation: College of Life Science, Jiaying University, Meizhou, 514015, People's Republic of China, xhx@jyu.edu.cn.
authors.forename: Heng
authors.initials: H
authors.lastname: Xu
authors.forename: Dong
authors.initials: D
authors.lastname: Shen
authors.forename: Xue-Qiang
authors.initials: XQ
authors.lastname: Wu
authors.forename: Zhi-Wei
authors.initials: ZW
authors.lastname: Liu
authors.forename: Qi-He
authors.initials: QH
authors.lastname: Yang
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D055162:Biocatalysis; D004795:Enzyme Stability; D005947:Glucose / Q000737:chemistry; D006207:Half-Life; D066248:High Fructose Corn Syrup / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D046950:Thermoanaerobacterium / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D066248:High Fructose Corn Syrup; D050505:Mutant Proteins; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D005947:Glucose