Item type: | Article | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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Journal or Publication Title: | Archives of microbiology | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Volume: | 182 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Number of Issue or Book Chapter: | 2-3 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Page Range: | pp. 226-35 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Date: | 2004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Institutions: | Biology, Preclinical Medicine > Institut für Biophysik und physikalische Biochemie > Prof. Dr. Reinhard Sterner | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Identification Number: |
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Classification: |
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Dewey Decimal Classification: | 500 Science > 570 Life sciences | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Status: | Published | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Refereed: | Yes, this version has been refereed | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Created at the University of Regensburg: | Yes | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Item ID: | 13681 |
Abstract
The thermoalkaliphilic anaerobic bacterium Anaerobranca gottschalkii produces an extracellular CGTase when grown on starch at 55 degrees C and pH 9.0. The gene encoding this CGTase was cloned and successfully expressed in Escherichia coli. It encodes a protein consisting of 721 amino acids with a signal sequence of 34 amino acids. On SDS-polyacrylamide gels, the purified CGTase from A. ...
Abstract
The thermoalkaliphilic anaerobic bacterium Anaerobranca gottschalkii produces an extracellular CGTase when grown on starch at 55 degrees C and pH 9.0. The gene encoding this CGTase was cloned and successfully expressed in Escherichia coli. It encodes a protein consisting of 721 amino acids with a signal sequence of 34 amino acids. On SDS-polyacrylamide gels, the purified CGTase from A. gottschalkii displayed the expected molecular mass of 78 kDa. The recombinant enzyme was purified with a yield of 13.5% and displayed a specific activity of 210 units/mg. This CGTase, which represents the first report of a CGTase from an anaerobic thermoalkaliphile, was active at a broad range of temperature and pH, namely 55-70 degrees C and pH 5-10. It completely converted amylose, amylopectin and native starch to cyclodextrins, preferentially alpha-cyclodextrin. With a longer incubation period, the alpha-cyclodextrin to beta-cyclodextrin ratio declined. Variations in substrate type and concentration influenced the product pattern. Increasing the substrate concentration (0.5-20.0%) and glucans containing branching points (alpha-1,6 glycosidic linkages) shifted the product pattern to: beta-cyclodextin > alpha-cyclodextrin > gamma-cyclodextrin. In addition to these cyclodextrins, larger cyclodextrins (>8 glucose units) were formed in the initial reaction period. The CGTase was stabilised against thermal inactivation by calcium ions and high substrate concentrations; and 5 mM of CaCl(2) shifted the apparent melting point of the enzyme from 60 degrees C to 69 degrees C.
Metadata last modified: 29 Sep 2021 07:37