SUBSTRATE SPECIFICITIES OF ASPERGILLUS-TERREUS ALPHA-ARABINOFURANOSIDASES

The substrate specificities of three purified Aspergillus terreus alph a-arabinofuranosidases, pi 7.5, 8.3 and 8.5, were studied using variou s isolated arabinose-containing polysaccharides and oligosaccharides a s substrates. In addition, their mode of action was compared with thos e of some other arabinose-releasing enzymes. All three A. terreus alph a-arabinofuranosidases preferred branched pectic polysaccharides, such as sugar beet arabinan and beta-1,4-arabinogalactans as substrates, b ut they were also able to release arabinose from linear arabinan, beta -1,3/1,6-arabinogalactans and different arabinoxylans. alpha-Arabinofu ranosidases pi 7.5 and pi 8.5 were able to hydrolyse arabinose from ol igosaccharide mixtures of wheat flour and larchwood arabinoxylans, for ming arabinose and linear xylo-oligosaccharides. However, isolated ara binoxylo-oligosaccharides (DP 3-5) with arabinose substituted at O-3 o f an internal xylose residue were only poorly degraded. Arabinose link ed to O-2 of either internal or non-reducing end xylose residues was n ot hydrolysed. (C) 1998 Elsevier Science Ltd. All rights reserved.