Cyclic glucans produced by the intramolecular transglycosylation activity of potato D-enzyme on amylopectin

Biochem Biophys Res Commun. 1998 Jun 18;247(2):493-7. doi: 10.1006/bbrc.1998.8817.


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.

MeSH terms

  • Amylopectin / chemistry
  • Amylopectin / metabolism*
  • Glucan 1,4-alpha-Glucosidase / metabolism
  • Glucans / biosynthesis*
  • Glucans / chemistry
  • Glycogen Debranching Enzyme System / metabolism*
  • Glycosylation
  • Models, Biological
  • Molecular Weight
  • Plants / metabolism
  • Solanum tuberosum / enzymology
  • Starch / metabolism


  • Glucans
  • Glycogen Debranching Enzyme System
  • Starch
  • Amylopectin
  • 4 alpha-glucanotransferase
  • Glucan 1,4-alpha-Glucosidase