Purification, characterization, and synergistic action of phytate-resistant alpha-amylase and alpha-glucosidase from Geobacillus thermodenitrificans HRO10.
The alpha-amylase (1, 4-alpha-d-glucanohydrolase; EC 3.2.1.1) and alpha-glucosidase (alpha-d-glucoside glucohydrolase; EC 3.2.1.20) secreted by Geobacillus thermodenitrificans HRO10 were purified to homogeneity (13.6-fold; 11.5% yield and 25.4-fold; 32.0% yield, respectively) through a series of steps. The molecular weight of alpha-amylase was 58kDa, as estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The alpha-amylase activity on potato starch was optimal at pH 5.5 and 80 degrees Celsius. In the presence of Ca(2+), the alpha-amylase had residual activity of more than 92% after 1h of incubation at 70 degrees Celsius. The alpha-amylase did not lose any activity in the presence of phytate (a selective alpha-amylase inhibitor) at concentrations as high as 10mM, rather it retained 90% maximal activity after 1h of incubation at 70 degrees Celsius. EGTA and EDTA were strong inhibitory substances of the enzyme. The alpha-amylase hydrolyzed soluble starch at 80 degrees Celsius, with a K(m) of 3.05mgml(-1) and a V(max) of 7.35Uml(-1). The molecular weight of alpha-glucosidase was approximately 45kDa, as determined by SDS-PAGE. The enzyme activity was optimal at pH 6.5-7.5 and 55 degrees Celsius. Phytate did not inhibit G. thermodenitrificans HRO10 alpha-glucosidase activity, whereas pCMB was a potent inhibitor of the enzyme. The alpha-glucosidase exhibited Michaelis-Menten kinetics with maltose at 55 degrees Celsius (K(m): 17mM; V(max): 23micromolmin(-1)mg(-1)). Thin-layer chromatography studies with G. thermodenitrificans HRO10 alpha-amylase and alpha-glucosidase showed an excellent synergistic action and did not reveal any transglycosylation catalyzed reaction by the alpha-glucosidase.
Ezeji
Thaddeus C
TC
University of Rostock, Institute of Biological Sciences, Division of Microbiology, Albert-Einstein-Str. 3, D-18051 Rostock, Germany. ezeji@uiuc.edu
Bahl
Hubert
H
D001406:Bacillaceae / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability / Q000187:drug effects; D065089:Glycoside Hydrolase Inhibitors; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D008970:Molecular Weight; D010833:Phytic Acid / Q000494:pharmacology*; D013213:Starch / Q000378:metabolism; D013379:Substrate Specificity; D000516:alpha-Amylases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000302:isolation & purification / Q000378:metabolism*
D001426:Bacterial Proteins; D065089:Glycoside Hydrolase Inhibitors; D010833:Phytic Acid; D013213:Starch; D000516:alpha-Amylases; D000520:alpha-Glucosidases; D002118:Calcium