Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Biotechnology & Applied Microbiology, Bacillus subtilis endoxylanase, Triticum aestivum xylanase inhibitor, inhibition sensitivity, site-directed mutagenesis, WHEAT-FLOUR, TAXI-I, XYLANASE INHIBITORS, BREAD-MAKING, PROTEIN, IDENTIFICATION, FRACTIONATION, SPECIFICITY, GLYCOSIDASE, RESIDUES, Amino Acid Sequence, Bacillus subtilis, Biotechnology, Endo-1,4-beta Xylanases, Enzyme Activation, Genetic Engineering, Molecular Sequence Data, Mutagenesis, Site-Directed, Protein Structure, Secondary, Protein Structure, Tertiary, Substrate Specificity, Triticum, 06 Biological Sciences, 09 Engineering, 10 Technology, 3001 Agricultural biotechnology, 3206 Medical biotechnology, 3601 Art history, theory and criticism

Abstract:

The Bacillus subtilis endoxylanase XynA (BSXY) is frequently used to improve the functionality of arabinoxylan-containing material in cereal based industries. The presence of endogenous Triticum aestivum xylanase inhibitors (TAXI-I and TAXI-II) in wheat is a real concern as they have a direct negative impact on the efficiency of this enzyme. Here, we used the recently determined structure of the complex between TAXI-I and an endoxylanase of Aspergillus niger to develop inhibitor-insensitive BSXY variants by site-directed mutagenesis of strategically chosen amino acids. We either induced steric hindrance to reject the inhibitors or interrupted key interactions with the inhibitors in the endoxylanase substrate-binding groove. The first strategy was successfully applied to position G12 where G12W combined inhibition insensitivity with unharmed catalytic performance. Variants from the second strategy showed altered inhibitor sensitivities concomitant with changes in enzyme activities and allowed to gain insight in the binding-mode of both TAXI-I and TAXI-II with BSXY.