Purification of TAXI-like endoxylanase inhibitors from wheat (Triticum aestivum L.) whole meal reveals a family of iso-forms

An affinity chromatography method has been developed for purification of endoxylanase inhibitors concentrated by cation exchange chromatography from wheat whole meal and is based on immobilisation of a Bacillus subtilis family 11 endoxylanase on N-hydroxysuccinimide activated Sepharose 4 Fast Flow. When followed by high-resolution cation exchange chromatography, the purification of seven TAXIs, Triticum aestivum L. endoxylanase inhibitors was achieved so extending the number of such proteins known to date (TAXI I and II). Based on their inhibition activities against a B. subtilis family 11 and an Aspergillus niger family 11 endoxylanase, six TAXI I- and only one TAXI II-like inhibitor could be distinguished. The first type of endoxylanase inhibitor is active against both endoxylanases and the second type only has significant activity against the B. subtilis endoxylanase.