Preliminary characterisation of endogenous wheat arabinoxylan-degrading enzymic extracts

Endogenous arabinoxylan-degrading enzymes in wheat were investigated in extracts of whole grains and tissues. Crude enzymes from two European cultivars were observed to hydrolyse various substrates, such as o-nitrophenyl beta-D-xylopyranoside, p-nitrophenyl alpha-L-arabinofuranoside, xylan, and water-extractable and water-unextractable wheat arabinoxylans. Viscosity measurements and gel permeation chromatography of digests of arabinoxylans by crude extracts indicated the presence of endo-acting enzymes. Moreover, high-performance anion-exchange chromatography showed that monomers (arabinose, xylose) and small xylooligosaccharides were also released. Wheat variety and han est year were shown to have little influence on the level of activity. Grains were fractionated on a laboratory mill and assays of the crude extracts obtained from the different fractions showed that the inner tissues were less active towards arabinoxylans and model substrates than the outer. (C) 1998 Academic Press.