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Applied and Environmental Microbiology, April 1999, p. 1644-1651, Vol. 65, No. 4
Department of Food Science and Technology and
Research Center for New Bio-Materials in Agriculture,
Received 28 October 1998/Accepted 8 February 1999
A maltogenic amylase gene was cloned in Escherichia
coli from a gram-negative thermophilic bacterium,
Thermus strain IM6501. The gene encoded an enzyme (ThMA)
with a molecular mass of 68 kDa which was expressed by the expression
vector p6xHis119. The optimal temperature of ThMA was 60°C, which was
higher than those of other maltogenic amylases reported so far. Thermal
inactivation kinetic analysis of ThMA indicated that it was stabilized
in the presence of 10 mM EDTA. ThMA harbored both hydrolysis and
transglycosylation activities. It hydrolyzed
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Modes of Action of Acarbose Hydrolysis and
Transglycosylation Catalyzed by a Thermostable Maltogenic Amylase, the
Gene for Which Was Cloned from a Thermus
Strain
-cyclodextrin and
starch mainly to maltose and pullulan to panose. ThMA not only
hydrolyzed acarbose, an amylase inhibitor, to glucose and
pseudotrisaccharide (PTS) but also transferred PTS to 17 sugar
acceptors, including glucose, fructose, maltose, cellobiose, etc.
Structural analysis of acarbose transfer products by using methylation,
thin-layer chromatography, high-performance ion chromatography, and
nuclear magnetic resonance indicated that PTS was transferred primarily
to the C-6 of the acceptors and at lower degrees to the C-3 and/or C-4.
The transglycosylation of sugar to
methyl-
-D-glucopyranoside by forming an
-(1,3)-glycosidic linkage was demonstrated for the first time by
using acarbose and ThMA. Kinetic analysis of the acarbose transfer
products showed that the C-4 transfer product formed most rapidly but
readily hydrolyzed, while the C-6 transfer product was stable and
accumulated in the reaction mixture as the main product.
*
Corresponding author. Mailing address: Department of
Food Science and Technology, Seoul National University, 103, Seodun
Dong, Kwonsun Gu, Suwon 441-744, Korea. Phone: 82-331-290-2582. Fax: 82-331-294-1336. E-mail: parkkh{at}plaza.snu.ac.kr.
Applied and Environmental Microbiology, April 1999, p. 1644-1651, Vol. 65, No. 4
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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