Purification and Characterization of a Novel Fungal α-Glucosidase from Mortierella alliacea with High Starch-hydrolytic Activity(Biochemistry & Molecular Biology)

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The fungal strain Mortierella alliacea YN-15 is an arachidonic acid producer that assimilates soluble starch despite having undetectable α-amylase activity. Here, a α-glucosidase responsible for the starch hydrolysis was purified from the culture broth through four-step column chromatography. Maltose and other oligosaccharides were less preferentially hydrolyzed and were used as a glucosyl donor for transglucosylation by the enzyme, demonstrating distinct substrate specificity as a fungal α-glucosidase. The purified enzyme consisted of two heterosubunits of 61 and 31 kDa that were not linked by a covalent bond but stably aggregated to each other even at a high salt concentration (0.5 M), and behaved like a single 92-kDa component in gel-filtration chromatography. The hydrolytic activity on maltose reached a maximum at 55℃ and in a pH range of 5.0-6.0, and in the presence of ethanol, the trans-glucosylation reaction to form ethyl-α-D-glucoside was optimal at pH 5.0 and a temperature range of 45-50℃.
2002-11-23