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  • Title: Cyclic glucans produced by the intramolecular transglycosylation activity of potato D-enzyme on amylopectin.
    Author: Takaha T, Yanase M, Takata H, Okada S, Smith SM.
    Journal: Biochem Biophys Res Commun; 1998 Jun 18; 247(2):493-7. PubMed ID: 9642157.
    Abstract:
    Potato D-enzyme catalyses an intramolecular transglycosylation reaction on amylose to produce cycloamylose, a novel cyclic alpha-1, 4 glucan. To determine if a similar activity could be observed with a high molecular weight branched substrate, recombinant potato D-enzyme was incubated with amylopectin. The substrate was converted into two fractions of lower molecular mass. Fraction I comprised 15% cyclic molecules of which the majority contained both alpha-1,4 and alpha-1,6 links. These were shown to be branched molecules with branches shorter than those in amylopectin. Fraction II comprised 80% cyclic molecules of which the majority contained only alpha-1,4 links (cycloamylose). Since fraction II appeared before fraction I, we propose that D-enzyme first catalysed the cyclisation of the outer side chains of amylopectin and then the cyclisation of inner chains to produce branched clusters. These results demonstrate that D-enzyme can catalyse the transfer of branched glucans, and suggest novel ways in which it may participate in starch metabolism in plants.
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