Heterologous expression and characterization of a novel xanthan lyase

Xanthan lyase is a kind of xanthan- modifying enzymes which are powerful tools for xanthan modification and xantho- oligosaccharide preparation.In this paper,a novel xanthan lyase- encoding gene xly was cloned and sequenced for the first time,from an excellent xanthan- degrading strain Microbacterium sp.XT11.The xly gene encoded a 122027 u protein,including a 35- amino acid signal peptide at N terminus and a 392- amino acid carbohydrate binding module( CBM) at C terminus. A mature enzyme without signal peptide and CBM was fused with a GST tag and the resulted XLY- GST could be expressed in Escherichia coli BL21( DE3) in a high level.The purified XLY- GST showed similar features with that of the wild type xanthan lyase.It was optimally active at p H6.0 and 40 ℃ and alkali- tolerant at a high p H value of 10.5.The metal ions including Ca2 +and Mn2 +strongly stimulated xanthan lyase activity but ion Cu2 +was its inhibitor.XLY- GST was specific on the pyruvated and mannosyl residue in the intact xanthan molecule.Our work should be valuable for preparing the xanthan lyase and studying the modification of xanthan side chain.