Triticum aestivum L. endoxylanase inhibitor (TAXI) consists of two inhibitors, TAXI I and TAXI II, with different specificities

The Triticum aestivum L. endoxylanase inhibitor (TAXI) discovered by Debyse r and Delcour [(1997) fur. Pat. filed April 1997, published as WO 98/49278] and Debyser, Derdelinckx and Delcour [(1997) J. Am. Sec. Brew. Chem. 55, 1 53-156] seems to be a mixture of two different endoxylanase inhibitors, cal led TAXI I and TAXI II. By using Aspergillus niger as veil as Bacillus subt ilis endoxylanases for assaying inhibition activity, both inhibitors could be purified to homogeneity from wheat (Triticum aestivum L.. var. Soissons) . TAXI I and TAXI II have similar molecular structures. They both have a mo lecular mass of approx. 40.0 kDa, are not glycosylated and occur in two mol ecular forms, i.e. a non-proteolytically processed one and a proteolyticall y processed one. However, the pi of TAXI II (at least 9.3) is higher than t hat of TAXI I (8.8). TAXI I and TAXI II clearly show different inhibition a ctivities towards different endoxylanases. The N-terminal amino acid sequen ces of both inhibitors show a high degree of identity, which might indicate that there is an evolutionary relationship between them.