Characterisation of the (1 leads to 4)-alpha-D-glucan-branching 6-glycosyltransferase by in vitro synthesis of branched starch polysaccharides
1992
Praznik, W. | Rammesmayer, G. | Spies, T. | Huber, A.
Starch branching enzyme (Q-enzyme; EC 2.4.1.18), isolated from young, mature potato tubers (Solanum tuberosum L.) and purified by ammonium sulfate precipitations, hydrophobic-interaction chromatography, and size-exclusion chromatography. was completely free of phosphorylase (EC 2.4.1.1) and alpha-amylase (EC 3.2.1.1) activity, had a molecular mass of 64 kDa, was homogeneous in SDS-PAGE, was inhibited by 4 X 10(-5)M oxidised gluthathione, and could be stored at -80 degrees in the presence of SH-reducing agents. The actions of Q-enzyme alone and in combination with potato phosphorylase on amylose, pea starch, potato amylose, potato amylopectin, and waxy maize was investigated. The combination gave high molecular weight polysaccharides, debranching of which yielded patterns of short and long chains similar to those of debranched amylopectin. Treatment of amylose with Q-enzyme resulted in a decrease in the molecular weight averages and broadening of the molecular weight distribution, and debranching of the product yielded a short-chain distribution pattern.
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