PRELIMINARY CHARACTERIZATION OF ENDOGENOUS WHEAT ARABINOXYLAN-DEGRADING ENZYMATIC EXTRACTS

Endogenous arabinoxylan-degrading enzymes in wheat were investigated i n extracts of whole grains and tissues. Crude enzymes from two Europea n cultivars were observed to hydrolyse various substrates, such as o-n itrophenyl beta-D-xylopyranoside, p-nitrophenyl alpha-L-arabinofuranos ide, xylan, and water-extractable and water-unextractable wheat arabin oxylans. Viscosity measurements and gel permeation chromatography of d igests of arabinoxylans by crude extracts indicated the presence of en do-acting enzymes. Moreover, high-performance anion-exchange chromatog raphy showed that monomers (arabinose, xylose) and small xylooligosacc harides were also released. Wheat variety and han est year were shown to have little influence on the level of activity. Grains were fractio nated on a laboratory mill and assays of the crude extracts obtained f rom the different fractions showed that the inner tissues were less ac tive towards arabinoxylans and model substrates than the outer. (C) 19 98 Academic Press.