title: Characterization of two novel family 12 xyloglucanases from the thermophilic Rhizomucor miehei.
abstract: Two novel glycoside hydrolase (GH) family 12 xyloglucanase genes (designated RmXEG12A and RmXEG12B) were cloned from the thermophilic fungus Rhizomucor miehei. Both genes contained open reading frames of 729 bp encoding 242 amino acids. Their deduced amino acid sequences shared 68% identity with each other and less than 60% with other xyloglucanases. The two genes, without the sequences for the signal peptides, were cloned and successfully expressed in Escherichia coli as active xyloglucanases, designated RmXEG12A and RmXEG12B, with similar molecular masses--25.6 and 25.9 kDa, respectively. RmXEG12A showed optimal activity at pH 6.5 and 65 °C, RmXEG12B at pH 5.0 and 60 °C. Both recombinant xyloglucanases displayed very high specific activities, 6,681.4 and 3,092.2 U mg(-1), respectively, toward tamarind xyloglucan, but no activity toward carboxymethylcellulose, Avicel, or p-nitrophenyl derivatives. The main products of tamarind xyloglucan hydrolysis by the two xyloglucanases were XXXG, XXLG/XLXG, and XLLG (where G is an unsubstituted β-D-Glc residue, X is a xylosylated β-D-Glc residue, and L is a β-D-Glc residue substituted by xylosyl-galactose).
authors: Department of Biotechnology, College of Food Science and Nutritional Engineering, China Agricultural University, No.17 Qinghua Donglu, Haidian District, Post Box 294, Beijing, 100083, China.
authors: Shuang
authors: S
authors: Song
authors: Yanbin
authors: Y
authors: Tang
authors: Shaoqing
authors: S
authors: Yang
authors: Qiaojuan
authors: Q
authors: Yan
authors: Peng
authors: P
authors: Zhou
authors: Zhengqiang
authors: Z
authors: Jiang
mesh_terms: D055162:Biocatalysis; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005936:Glucans / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D005810:Multigene Family; D020103:Rhizomucor / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D006026:Glycoside Hydrolases; C072818:xyloglucan endo(1-4)-beta-D-glucanase