Title: TLXI, a novel type of xylanase inhibitor from wheat (Triticum aestivum) belonging to the thaumatin family
Authors: Fierens, Ellen ×
Rombouts, Sigrid
Gebruers, Kurt
Goesaert, Hans
Brijs, Kristof
Beaugrand, Johnny
Volckaert, Guido
Van Campenhout, Steven
Proost, Paul
Courtin, Christophe
Delcour, Jan #
Issue Date: May-2007
Publisher: Published by Portland Press on behalf of the Biochemical Society
Series Title: Biochemical Journal vol:403 pages:583-591
Abstract: Wheat (Triticum aestivum) contains a previously unknown type of xylanase (EC inhibitor, which is described in the present paper for the first time. Based on its > 60 % similarity to TLPs (thaumatin-like proteins) and the fact that it contains the Prosite PS00316 thaumatin family signature, it is referred to as TLXI (thaumatin-like xylanase inhibitor). TLXI is a basic (pI >=, 9.3 in isoelectric focusing) protein with a molecular mass of approx. 18 kDa (determined by SDS/PAGE) and it occurs in wheat with varying extents of glycosylation. The TLXI gene sequence encodes a 26-amino-acid signal sequence followed by a 151-amino-acid mature protein with a calculated molecular mass of 15.6 kDa and pl of 8.38. The mature TLXI protein was expressed successfully in Pichia pastoris, resulting in a 21 kDa (determined by SDS/PAGE) recombinant protein (rTLXI). Polyclonal antibodies raised against TLXI purified from wheat react with epitopes of rTLXI as well as with those of thaumatin, demonstrating high structural similarity between these three proteins. TLXI has a unique inhibition specificity. It is a noncompetitive inhibitor of a number of glycoside hydrolase family 11 xylanases, but it is inactive towards glycoside hydrolase family 10 xylanases, Progress curves show that TLXI is a slow tight-binding inhibitor, with a K-i of approx. 60 nM. Except for zeamatin, an alpha-amylase/trypsin inhibitor from maize (Zea mays), no other enzyme inhibitor is currently known among the TLPs. TLXI thus represents a novel type of inhibitor within this group of proteins.
ISSN: 0264-6021
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division of Gene Technology (-)
Centre for Food and Microbial Technology
Laboratory of Molecular Immunology (Rega Institute)
× corresponding author
# (joint) last author

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