Characterisation of a recombinant β-xylosidase (xylA) from Aspergillus oryzae expressed in Pichia pastoris
Kirikyali, Narin and Wood, Jonathan and Connerton, Ian F. (2014) Characterisation of a recombinant β-xylosidase (xylA) from Aspergillus oryzae expressed in Pichia pastoris. AMB Express, 4 (68). pp. 1-7. ISSN 2191-0855
Official URL: http://www.amb-express.com/content/4/1/68
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.
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