Molecular Characterization of a Thermophilic and Salt- and Alkaline-Tolerant Xylanase from Planococcus sp. SL4, a Strain Isolated from the Sediment of a Soda Lake.
To enrich the genetic resource of microbial xylanases with high activity and stability under alkaline conditions, a xylanase gene (xynSL4) was cloned from Planococcus sp. SL4, an alkaline xylanase-producing strain isolated from the sediment of soda lake Dabusu. Deduced XynSL4 consists of a putative signal peptide of 29 residues and a catalytic domain (30-380 residues) of glycosyl hydrolase family 10, and shares the highest identity of 77% with a hypothetical protein from Planomicrobium glaciei CHR43. Phylogenetic analysis indicated that deduced XynSL4 is closely related with thermophilic and alkaline xylanases from Geobacillus and Bacillus species. The gene xynSL4 was expressed heterologously in Escherichia coli and the recombinant enzyme showed some superior properties. Purified recombinant XynSL4 (rXynSL4) was highly active and stable over the neutral and alkaline pH range from 6 to 11, with maximum activity at pH 7 and more than 60% activity at pH 11. It had an apparent temperature optimum of 70°C and retained stable at this temperature in the presence of substrate. rXynSL4 was highly halotolerant, retaining more than 55% activity with 0.25-3.0 M NaCl and was stable at the concentration of NaCl up to 4M. The enzyme activity was significantly enhanced by β-mercaptoethanol and Ca(2+) but strongly inhibited by heavy-metal ions and SDS. This thermophilic and alkaline- and salt-tolerant enzyme has great potential for basic research and industrial applications.
College of Biological Science and Technology, Fuzhou University, Fuzhou 350108, P.R. China.
Xiaoyun
X
Huang
College of Biological Science and Technology, Fuzhou University, Fuzhou 350108, P.R. China.|Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou 350002, P.R. China.
Juan
J
Lin
College of Biological Science and Technology, Fuzhou University, Fuzhou 350108, P.R. China.|Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou 350002, P.R. China.
Xiuyun
X
Ye
College of Biological Science and Technology, Fuzhou University, Fuzhou 350108, P.R. China.|Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou 350002, P.R. China.
Guozeng
G
Wang
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002681:China; D003001:Cloning, Molecular; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004795:Enzyme Stability; D019015:Geologic Sediments / Q000382:microbiology*; D060106:Lakes / Q000382:microbiology*; D008969:Molecular Sequence Data; D058642:Planococcus Bacteria / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment
D001426:Bacterial Proteins; D043364:Endo-1,4-beta Xylanases