Endo-β-1,4-xylanase inhibitors in leaves and roots of germinated maize

Extracts of both leaves and roots of germinated maize were found to contain endo-beta-1,4-xylanase inhibitors, previously reported only from whole maize meal. The inhibitors seem to be of the xylanase inhibitor protein (XIP) type, since they inhibit endoxylanases of families 10 and 11 and also show some other characteristics similar to XIP inhibitors described in other cereals. Inhibitors from leaves and roots appeared to be similar. A novel property of the inhibitors described in this work is their unusual thermostability. The half-life of inhibitors at pH 4.5 and 100 degrees C is greater than 10 h. However, the inhibitors are less thermostable at higher pH levels. Because they did not inhibit a plant endoxylanase, the inhibitors may play a role in maize defense against phytopathogens. (c) 2007 Elsevier Ltd. All rights reserved.