Purification and some properties of an extremely thermostable trehalose-hydrolyzing alpha-glucosidase from Bacillus flavocaldarius KP1228
1998
Murakami, S. | Yagami, M. | Suzuki, Y.
An intracellular trehalose-hydrolase of the extreme thermophile Bacillus flavocaldarius KP1228 (FERM-P9542) was purified to homogeneity. The molecular weight of the enzyme was estimated as 102,000 by sodium dodecylsulfate-polyacrylamide gel electrophoresis, but as 420,000 by gel filtration and gel electrophoresis under native conditions. Its Stoke's radius, frictional ratio and isoelectric point were estimated as 7.0 nm, 1.4 and 4.43, respectively. The enzyme was most active at 78 degrees C and pH 6.2. Its half-life was 10 min at 90 degrees C and pH 6.5. The enzyme hydrolyzed alpha-glucosidic bonds of trehalose, maltose, sucrose and p-nitrophenyl-alpha-D-glucopyranoside (each at 10 mM) with respective relative rates of 100, 130, 11 and 7.8 at 80 degrees C and pH6.8, but neither of alpha-glucosidic bonds in isomaltose, dextrin nor soluble starch. The Michaelis constant and the molecular activity (/subunit) were 85 mM and 4.0 s(-1) for trehalose, and 61mM and 4.2 s(-1) for maltose, respectively. We have suggested that the enzyme is a novel thermostable homotetrameric alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2. 1.20) active on both alpha-1,1 bond of trehalose and alpha-1,4 bond of maltose.
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