Targeted molecular engineering of a family 11 endoxylanase to decrease its sensitivity towards Triticum aestivum endoxylanase inhibitor types.
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.
Bourgois
Tine M
TM
Katholieke Universiteit Leuven, Laboratory of Gene Technology, Kasteelpark Arenberg 21, B-3001 Leuven, Belgium. tine.bourgois@biw.kuleuven.be
Nguyen
Dung V
DV
Sansen
Stefaan
S
Rombouts
Sigrid
S
Beliën
Tim
T
Fierens
Katleen
K
Raedschelders
Gert
G
Rabijns
Anja
A
Courtin
Christophe M
CM
Delcour
Jan A
JA
Van Campenhout
Steven
S
Volckaert
Guido
G
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics; D001709:Biotechnology; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004789:Enzyme Activation; D005818:Genetic Engineering / Q000379:methods*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000379:methods; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D014908:Triticum / Q000201:enzymology* / Q000235:genetics*
D043364:Endo-1,4-beta Xylanases