When grown on arabinoxylan as the sole carbon Source, the cereal phytopathogen Fusarium graminearum expresses four xylanases. Cloning and heterologous expression of the corresponding xylanase encoding genes and analysis of general biochemical properties, substrate specificities and inhibition sensitivities revealed some marked differences. XyIA and XyIB are glycoside hydrolase family (GH) I I xylanases, while XyIC and XyID) belong to GH 10. pH and temperature for optimal activity of the enzymes were between 6.0 and 7.0 and 40 degrees C, respectively. interestingly, XyIC displayed remarkable pH stability as it retained most of its activity even after pre-incubation at pH 1.0 and 13.0 for 120 min at room temperature. All xylanases hydrolysed xylotetraose, xylopentaose and xylohexaose, but to different extents, while only XyIC and XyID hydrolysed xylotriose. The two GH 10 xylanases released a higher percentage of smaller products from xylan and xylo-oligosaccharides than did their GH11 counterparts. Analysis of kinetic properties revealed that wheat arabinoxylan is the favoured XyIC Substrate while XyIA and XyIB prefer sparsely substituted oat spelt xylan. XyIC and XyID were inhibited by xylanase inhibiting protein (XIP), while XyIA and XyIB were sensitive to Triticum aestivum xylanase inhibitor (TAXI). Because of its pH stability and preference for arabinoxylan, XyIC is a valuable candidate for use in biotechnological applications. (C) 2008 Elsevier Inc. All rights reserved.