Fungal xylanase inhibitor. Possesses competitive inhibiting activity against fungal endo-1,4-beta-D-xylanases belonging to glycoside hydrolase family 10 (GH10) and family 11 (GH11). Possesses also inhibitory activity towards barley alpha-amylases. Binding to xylanases or amylases is necessary for inhibition activity. May function in plant defense against secreted fungal pathogen xylanases. Is similar to class III chitinases, but does not exhibit chitinase activity. Binds to fungal GH10 and GH11 xylanases. Forms also a ternary complex with barley alpha-amylase 1 (AMY1) and insoluble starch. Expressed in immature embryos 3 weeks after pollination, in roots and shoots of 3 day and 5 day old seedlings, and in roots of 10 day old seedlings. By wounding, methyl jasmonate, and by E.graminis infection in leaves. Belongs to the glycosyl hydrolase 18 family. Xylanase inhibitor subfamily.