Purification and biochemical characterization of an α‐glucosidase from Xanthophyllomyces dendrorhous

Xanthophyllomyces dendrorhous grown in different media shows amylolytic activity, consisting in an extracellular exo‐acting enzyme able to hydrolysed α,1–4 glycosidic bonds from soluble starch, which also cleaves maltose and malto‐oligosaccharides. The enzyme was purified, using basically a couple of chromatography process on DEAE–Sephacel. It is a glycoprotein with a molecular weight estimated to be 60.2 kDa based on its mobility in SDS–PAGE and 115 kDa based on gel filtration. N‐linked carbohydrate accounts for 12% of the total mass. It exhibited optimum activity at pH 5.5 and 45 °C. Thermostability analysis indicated that it was stable to thermal treatment up to 50 °C; 50% of the activity was maintained after 3 h. The rate parameters measured for the hydrolysis of starch and various chain length malto‐oligosaccharides shows high catalytic efficiency, calculated by the relationship Vcat/Km, for malto‐oligosaccharides, such as maltotriose (873 mM−1 min−1), or maltoheptose (698 mM−1 min−1). The new enzyme hydrolysed soluble starch with nearly 3.5‐ and 1.4‐fold lower efficiency than that for maltotriose and maltose, respectively. No activity was found on heterogeneous substrates, such as sucrose and aryl α‐glucoside, or on isomalto‐oligosaccharides. In accordance to substrate specificity profile, the new enzyme was classified as an α‐glucosidase. Copyright © 2006 John Wiley & Sons, Ltd.