Substrate specificities of Aspergillus terreus α-arabinofuranosidases

Abstract

The substrate specificities of three purified Aspergillus terreus α-arabinofuranosidases, pI 7.5, 8.3 and 8.5, were studied using various isolated arabinose-containing polysaccharides and oligosaccharides as substrates. In addition, their mode of action was compared with those of some other arabinose-releasing enzymes. All three A. terreus α-arabinofuranosidases preferred branched pectic polysaccharides, such as sugar beet arabinan and β-1,4-arabinogalactans as substrates, but they were also able to release arabinose from linear arabinan, β-1,3/1,6-arabinogalactans and different arabinoxylans. α-Arabinofuranosidases pI 7.5 and pI 8.5 were able to hydrolyse arabinose from oligosaccharide mixtures of wheat flour and larchwood arabinoxylans, forming arabinose and linear xylo-oligosaccharides. However, isolated arabinoxylo-oligosaccharides (DP 3-5) with arabinose substituted at O-3 of an internal xylose residue were only poorly degraded. Arabinose linked to O-2 of either internal or non-reducing end xylose residues was not hydrolysed.