Distribution of the O-acetyl groups and β-galactofuranose units in galactoxylomannans of the opportunistic fungus Cryptococcus neoformans

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DOIResolve DOI: http://doi.org/10.1093/glycob/cww127
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TypeArticle
Journal titleGlycobiology
ISSN0959-6658
1460-2423
Article numbercww127
Subjectcryptococcus; galactofuranose; galactoxylomannans; O-acetyl; capsular; polysaccharides
AbstractGalactoxylomannans (GalXMs) are a mixture of neutral and acidic capsular polysaccharides produced by the human opportunistic fungus Cryptococcus neoformans that exhibit potent suppressive effects on the host immune system. Previous studies describing the chemical structure of C. neoformans GalXMs have reported species without O-acetyl substituents. Herein we describe that C. neoformans grown in capsule-inducing medium produces highly O-acetylated GalXMs. The location of the O-acetyl groups was determined by nuclear magnetic resonance (NMR) spectroscopy. In the neutral GalXM (NGalXM), 80% of 3-linked mannose (α-Manp) residues present in side chains are acetylated at the O-2 position. In acidic GalXM also termed glucuronoxylomannogalactan (GXMGal), 85% of the 3-linked α-Manp residues are acetylated either in the O-2 (75%) or in the O-6 (25%) position, but O-acetyl groups are not present at both positions simultaneously. In addition, NMR spectroscopy and methylation analysis showed that β-galactofuranose (β-Galf) units are linked to O-2 and O-3 positions of nonbranched α-galactopyranose (α-Galp) units present in the GalXMs backbone chain. These findings highlight new structural features of C. neoformans GalXMs. Among these features, the high degree of O-acetylation is of particular interest, since O-acetyl group-containing polysaccharides are known to possess a range of immunobiological activities.
Publication date
PublisherOxford University Press
LanguageEnglish
AffiliationHuman Health Therapeutics; National Research Council Canada
Peer reviewedYes
NPARC number23001336
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Record identifier4d9c7bd1-5607-4ee9-9787-19761f45791a
Record created2017-01-19
Record modified2017-01-26
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