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Structure and assembly of epiglucan, the extracellular (1→3;1→6)-β-glucan produced by the fungusEpicoccum nigrumstrain F19

Authors
Journal
Carbohydrate Research
0008-6215
Publisher
Elsevier
Publication Date
Volume
341
Issue
3
Identifiers
DOI: 10.1016/j.carres.2005.10.013
Keywords
  • β-Glucan Assembly
  • Epiglucan Elongation
  • Side Chain Insertion
  • Extracellular Polysaccharide
  • Nmr Spectroscopy
  • Biosynthesis
  • Radioisotope Labelling

Abstract

Abstract In a previous article [ Carbohydr. Res. 2001, 331, 163–171] two different structures for the possible modular repeating unit of the extracellular β-glucan, epiglucan produced by the fungus Epicoccum nigrum strain F19 were proposed. Clarifying which was the more likely one was considered essential before attempts were made to understand how epiglucan was assembled by this fungus. Data from Smith degradation analyses of epiglucan were consistent with the repeating unit of structure I, where single glucosyl residues are attached by (1→6)-β-linkages to two out of every three glucosyl residues in the (1→3)-β-linked glucan backbone. Repeated Smith degradations of 14C-glucose labelled epiglucan showed that chain elongation occurred from its non-reducing end. Side chain insertion into the growing glucan was followed by analysis of real time incorporation of 13C-glucose into epiglucan by 13C NMR, and 14C-glucose by enzymic digestion of the synthesised 14C-epiglucan. All data obtained were consistent with the view that single (1→6)-β-linked glucosyl side residues are inserted simultaneously as the glucan backbone elongates.

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