title: [Expression and characterization of a neutral Enterobacter cloacae GX-3 invertase].
abstract: OBJECTIVE
  To characterize a neutral invertase from Enterobacter cloacae GX-3.
  
  
  METHODS
  By searching GenBank database, we found the genes encoding invertase from the same genus Enterobacter. These sequences were aligned and analyzed. Then, a gene encoding neutral invertase was amplified by PCR. The recombinant plasmid pQE-Einv was constructed. We purified the expressed protein Einv with nickel-nitrilotriacetic acid chromatography. At last, the characterics of the recombinant protein Einv were studied in detail.
  
  
  RESULTS
  A gene encoding neutral invertase was discovered and cloned from E. cloacae GX-3. The recombinant enzyme Einv was characterized. Einv had an optimum pH of 6.5 and an optimum temperature of 40 degrees C. The results of sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE) and gel permeation chromatography ( GPC) showed that Einv was a homo-dimer protein. Einv retained 80% activity at sucrose concentrations up to 1170 mmol/L. But, Einv had no transglycosylation activity at high sucrose concentration. It could hydrolyze raffinose, 1-kestose, nystose, fructofuranosylnystose and stachyose.
  
  
  CONCLUSIONS
  It is first reported that an invertase from Enterobacter cloacae is a beta-fructofuranosidase at neutral pH range. It only has hydrolysis activity without tranglycosylation activity. These characteristics indicate that the neutral invertase Einv has important applications in food industry.
authors.forename: Yingli
authors.initials: Y
authors.lastname: Zhao
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Wu
authors.forename: Zhikai
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zilong
authors.initials: Z
authors.lastname: Wang
authors.forename: Yutuo
authors.initials: Y
authors.lastname: Wei
authors.forename: Ribo
authors.initials: R
authors.lastname: Huang
authors.forename: Liqin
authors.initials: L
authors.lastname: Du
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D016972:Enterobacter cloacae / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature; D043324:beta-Fructofuranosidase / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D043324:beta-Fructofuranosidase