Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Purified and biochemically characterised barley endoxylanase inhibitors

By using classical biochemical and affinity chromatographical techniques, two types of endoxylanase inhibitors were purified and characterised from barley, i.e. the Hordeum vulgare endoxylanase inhibitor (HVXI) and the endoxylanase inhibiting protein (XIP)-type inhibitor.

HVXI occurs as two molecular forms, both with a molecular weight (MW) of ca. 40,000. It strongly inhibits endoxylanases from glycoside hydrolase family 11, while no inhibition is found against those of family 10.

In contrast to HVXI, the barley XIP-type inhibitor is monomeric with a MW of ca. 30,000 and shows a strong inhibition against fungal endoxylanases, while bacterial endoxylanases were not inhibited at all by the barley XIP-type inhibitor.

Both types of inhibitors play probably an important role in plant protection mechanisms against microbial endoxylanases. Therefore, selection of barley cultivars with high endoxylanase inhibitor levels may in the future lead to decreased levels of fungicides.

Due the presence of endoxylanase inhibitors in barley, the activity and functionality of endoxylanases in barley-based processes (e.g. bread-making, beer production, feed industry) will be influenced. Inhibition sensitive endoxylanases will progressively lose their activity during processing, resulting in the need of higher endoxylanase dosages compared to inhibition insensitive endoxylanases. While endoxylanase inhibitors are undesirable in bread-making, they are beneficial in the refrigerated dough industry because they can reduce the action of endogenous endoxylanases, which form an undesirable brown liquid during dough storage.

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Katholieke Universiteit Leuven, Laboratory of Food Chemistry
Kasteelpark Arenberg 20
3001 Heverlee
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