title: Identification and characterization of a novel trehalose synthase gene derived from saline-alkali soil metagenomes.
abstract: A novel trehalose synthase (TreS) gene was identified from a metagenomic library of saline-alkali soil by a simple activity-based screening system. Sequence analysis revealed that TreS encodes a protein of 552 amino acids, with a deduced molecular weight of 63.3 kDa. After being overexpressed in Escherichia coli and purified, the enzymatic properties of TreS were investigated. The recombinant TreS displayed its optimal activity at pH 9.0 and 45 °C, and the addition of most common metal ions (1 or 30 mM) had no inhibition effect on the enzymatic activity evidently, except for the divalent metal ions Zn(2+) and Hg(2+). Kinetic analysis showed that the recombinant TreS had a 4.1-fold higher catalytic efficiency (Kcat/K m ) for maltose than for trehalose. The maximum conversion rate of maltose into trehalose by the TreS was reached more than 78% at a relatively high maltose concentration (30%), making it a good candidate in the large-scale production of trehalsoe after further study. In addition, five amino acid residues, His172, Asp201, Glu251, His318 and Asp319, were shown to be conserved in the TreS, which were also important for glycosyl hydrolase family 13 enzyme catalysis.
authors.affiliation: College of Food Science and Light Industry, Nanjing University of Technology, Nanjing, People's Republic of China.
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Ming
authors.initials: M
authors.lastname: Lin
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yanping
authors.initials: Y
authors.lastname: Li
authors.forename: Xian
authors.initials: X
authors.lastname: Xu
authors.forename: Shuang
authors.initials: S
authors.lastname: Li
authors.lastname: He Huang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004789:Enzyme Activation; D015870:Gene Expression; D015723:Gene Library; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D054892:Metagenome; D008670:Metals; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011487:Protein Conformation; D011994:Recombinant Proteins; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D007477:Ions; D008670:Metals; D011994:Recombinant Proteins; D012987:Soil; D005964:Glucosyltransferases; C099692:trehalose synthase