title: Purification and characterization of a novel fungal alpha-glucosidase from Mortierella alliacea with high starch-hydrolytic activity.
abstract: The fungal strain Mortierella alliacea YN-15 is an arachidonic acid producer that assimilates soluble starch despite having undetectable alpha-amylase activity. Here, a alpha-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 alpha-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 degrees C and in a pH range of 5.0-6.0, and in the presence of ethanol, the transglucosylation reaction to form ethyl-alpha-D-glucoside was optimal at pH 5.0 and a temperature range of 45-50 degrees C.
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Tsunehiro
authors.initials: T
authors.lastname: Aki
authors.forename: Yûki
authors.initials: Y
authors.lastname: Hidaka
authors.forename: Yûji
authors.initials: Y
authors.lastname: Furuya
authors.forename: Seiji
authors.initials: S
authors.lastname: Kawamoto
authors.forename: Seiko
authors.initials: S
authors.lastname: Shigeta
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Ono
authors.forename: Osamu
authors.initials: O
authors.lastname: Suzuki
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D002853:Chromatography, Liquid / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004795:Enzyme Stability; D005947:Glucose / Q000032:analysis / Q000096:biosynthesis; D006031:Glycosylation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008320:Maltose / Q000378:metabolism; D020094:Mortierella / Q000145:classification / Q000201:enzymology*; D021122:Protein Subunits / Q000737:chemistry; D013213:Starch / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature; D000520:alpha-Glucosidases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D008320:Maltose; D013213:Starch; D000520:alpha-Glucosidases; D005947:Glucose