Production of substrate for galactose oxidase by depolymerization of an arabinogalactan-peptide from wheat flour

Water extractable arabinogalactan-peptide (WE-AGP) isolated from white whea t flour was depolymerized enzymatically to liberate substrate for a galacto se oxidase from Dactylium dendroides. A crude liquid pectolytic preparation from Aspergillus niger (p70) displayed activities capable of converting WE -AGP into a substrate for galactose oxidase. The most favorable substrate w as observed when WE-AGP was not fully depolymerized into galactose and arab inose, alpha-L-Arabinofuranosidase B from A. niger was also able to produce substrate from WE-AGP; arabinofuranosidase-treated WE-AGP was a better sub strate for galactose oxidase than galactose. Treatment by the crude p70 and purified enzymes showed that alpha-L-arabinofuranosidase was partly respon sible for the production of substrate, whereas beta-galactosidase did not r esult in any substrate production or improve the effect of alpha-L-arabinof uranosidase. However, the positive effect of alpha-L-arabinofuranosidase wa s increased when p70 was added at the same level of arabinofuranosidase act ivity, suggesting that additional enzyme activities present in p70 were res ponsible for production of substrate for galactose oxidase.