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Characterisation of a recombinant β-xylosidase (xylA) from Aspergillus oryzae expressed in Pichia pastoris

Kirikyali, Narin; Wood, Jonathan; Connerton, Ian F.

Authors

Narin Kirikyali

Jonathan Wood

Ian F. Connerton ian.connerton@nottingham.ac.uk

Abstract

β-xylosidases catalyse the hydrolysis of short chain xylooligosaccharides from their non-reducing ends into xylose. In this study we report the heterologous expression of Aspergillus oryzae β-xylosidase (XylA) in Pichia pastoris under the control of the glyceraldehyde-3-phosphate dehydrogenase promoter. The recombinant enzyme was optimally active at 55°C and pH 4.5 with Km and Vmax values of 1.0 mM and 250 μmol min−1 mg−1 respectively against 4-nitrophenyl β-xylopyranoside. Xylose was a competitive inhibitor with a Ki of 2.72 mM, whereas fructose was an uncompetitive inhibitor reducing substrate binding affinity (Km) and conversion efficiency (Vmax). The enzyme was characterised to be an exo-cutting enzyme releasing xylose from the non-reducing ends of β-1,4 linked xylooligosaccharides (X2, X3 and X4). Catalytic conversion of X2, X3 and X4 decreased (Vmax and kcat) with increasing chain length.

Journal Article Type Article
Publication Date Aug 31, 2014
Journal AMB Express
Electronic ISSN 2191-0855
Publisher Humana Press
Peer Reviewed Peer Reviewed
Volume 4
Issue 68
DOI https://doi.org/10.1186/s13568-014-0068-1
Publisher URL http://www.amb-express.com/content/4/1/68
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0

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