Properties of the Glucan Branching Enzyme of the Hyperthermophilic Bacterium Aquifex aeolicus

• Published in: Biocatalysis and biotransformation Vol. 21; no. 4-5; pp. 199 - 207
• Main Authors: van der Maarel, M. J. E. C., Vos, A., Sanders, P., Dijkhuizen, L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Abingdon Informa UK Ltd. (Informa Healthcare, Taylor & Francis AS) 01.10.2003; Taylor & Francis; Taylor and Francis
• Subjects: Aquifex aeolicus; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Fundamental and applied biological sciences. Psychology; Glucan branching enzyme; Glycoside hydrolase; Miscellaneous; Mission oriented research; Starch; Thermostability; α-amylase superfamily; 1,4-α-Glucan branching enzyme; Thermostability; Enzyme; Hyperthermophily; Starch; α-amylase superfamily; Transferases; Glycosyltransferases; Hexosyltransferases; Glucan branching enzyme; Aquifex aeolicus; Glycoside hydrolase
• ISSN: 1024-2422; 1029-2446
• DOI: 10.1080/10242420310001618528

Abstract Glucan branching enzymes are responsible for the synthesis of α(1→6) glycosidic bonds in glycogen and amylopectin. The glucan branching enzyme of the hyperthermophile Aquifex aeolicus is the most thermoactive and thermostable glucan branching enzyme described. The gene encoding this glucan branching enzyme was overexpressed in E. coli and purified using γ-cyclodextrin affinity chromatography. Subsequently, the enzyme was stable up to 90°C. Its thermostability may be explained by the relatively high number of aromatic amino acid residues present, in combination with a relatively low number glutamine/asparagine residues. The Km for amylose was 4µM and the Vmax was 4.9 U/mg of protein (at optimal pH and temperature). The side-chain distribution of the branched glucan formed from amylose was determined.