Catalytic properties of a GH10 endo-β-1,4-xylanase from Streptomyces thermocarboxydus HY-15 isolated from the gut of Eisenia fetida

• Published in: Journal of molecular catalysis. B, Enzymatic Vol. 62; no. 1; pp. 32 - 39
• Main Authors: Kim, Do Young, Han, Mi Kyoung, Oh, Hyun-Woo, Park, Doo-Sang, Kim, Su-Jin, Lee, Seung-Goo, Shin, Dong-Ha, Son, Kwang-Hee, Bae, Kyung Sook, Park, Ho-Yong
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2010; Elsevier
• Subjects: Bioconversions. Hemisynthesis; Biological and medical sciences; Biotechnology; Endo-β-1,4-xylanase; Fundamental and applied biological sciences. Psychology; Glycoside hydrolase family 10; Methods. Procedures. Technologies; p-Nitrophenylcellobioside; PNP-cellobioside; Streptomyces thermocarboxydus HY-15; p-Nitrophenylcellobioside; Streptomyces thermocarboxydus HY-15; Endo-β-1,4-xylanase; Glycoside hydrolase family 10; PNP-cellobioside; Streptomycetaceae; Enzyme; Gut; Streptomyces; Endo-1,4-β-xylanase; Actinomycetales; Glycosylases; Glycosidases; Bacteria; Hydrolases; Actinomycetes; Glycoside
• ISSN: 1381-1177; 1873-3158
• DOI: 10.1016/j.molcatb.2009.08.015

A novel GH10 endo-β-1,4-xylanase (XylG) gene from Streptomyces thermocarboxydus HY-15, which was isolated from the gut of Eisenia fetida, was cloned, over-expressed, and characterized. The XylG gene (1182 bp) encoded a polypeptide of 393 amino acids with a deduced molecular mass of 43,962 Da and a calculated pI of 6.74. The primary structure of XylG was 69% similar to that of Thermobifida fusca YX endo-β-1,4-xylanase. It was most active at pH 6.0 and 55 °C. The susceptibilities of xylans to XylG were as follows: oat spelt xylan > birchwood xylan > beechwood xylan. The XylG also showed high activity (474 IU/mg) toward p-nitrophenylcellobioside. Moreover, at pH 6.0 and 50 °C, the V max and K m values of the XylG were 127 IU/mg and 2.51 mg/ml, respectively, for oat spelt xylan and 782 IU/mg and 5.26 mM, respectively, for p-nitrophenylcellobioside. A homology model indicated that XylG folded to form a (β/α) 8-barrel with two catalytic residues of an acid/base (Glu181) and a nucleophile (Glu289). The formation of a disulfide bond between Cys321 and Cys327 were predicted by homology modeling.