MODE OF ACTION OF THE XYLAN-DEGRADING ENZYMES FROM ASPERGILLUS-AWAMORI ON ALKALI-EXTRACTABLE CEREAL ARABINOXYLANS

Alkali-extractable cereal arabinoxylan and oligosaccharides of known s tructure derived from it by enzymic hydrolysis were treated with endo- (1 --> 4)-beta-D-xylanases I and III from Aspergillus awamori CMI 1427 17 and the digests subjected to analysis by high performance anion-exc hange chromatography. Clear differences in the mode of action of the t wo endo-(1 --> 4)-beta-D-xylanases were observed. When counting from t he reducing end, at least one unsubstituted xylopyranosyl residue adja cent to singly substituted xylopyranosyl residues or two unsubstituted xylopyranosyl residues adjacent to doubly substituted xylopyranosyl r esidues cannot be removed by endo-(1 --> 4)-beta-D-xylanase I. At leas t two unsubstituted xylopyranosyl residues adjacent to singly or doubl y substituted xylopyranosyl residues cannot be removed by endo-(1 --> 4)-beta-D-xylanase III. Beta-D-Xylosidase from the same xylanolytic sy stem was able to remove terminal xylopyranosyl residues from the nonre ducing end of branched oligosaccharides only when two contiguous unsub stituted xylopyranosyl residues were present adjacent to singly or dou bly substituted xylopyranosyl residues.