| Dokumentenart: | Artikel | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Titel eines Journals oder einer Zeitschrift: | Archives of microbiology | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Band: | 182 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Nummer des Zeitschriftenheftes oder des Kapitels: | 2-3 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Seitenbereich: | S. 226-35 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Datum: | 2004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Institutionen: | Biologie und Vorklinische Medizin > Institut für Biophysik und physikalische Biochemie > Prof. Dr. Reinhard Sterner | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Identifikationsnummer: |
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| Dewey-Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Status: | Veröffentlicht | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Begutachtet: | Ja, diese Version wurde begutachtet | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| An der Universität Regensburg entstanden: | Ja | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Dokumenten-ID: | 13681 |
Zusammenfassung
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. ...
Zusammenfassung
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.
Metadaten zuletzt geändert: 29 Sep 2021 07:37
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