Assimilation of Xylose, Mannose, and Mannitol for Synthesis of Glucuronoxylomannan of Cryptococcus neoformans Determined by ¹³ C Nuclear Magnetic Resonance Spectroscopy

Abstract

Cryptococcus neoformans NIH 409 was cultured in a defined medium containing d-[1-13C]xylose (Xyl), d-[1-13C]mannose (Man), ord-[1-13C]mannitol as the sole carbon source. The distribution of 13C in the Man, Xyl, glucuronic acid (GlcA), and O-acetyl constituents of native and de-O-acetylated glucuronoxylomannan (GXM) was determined by one-dimensional13C nuclear magnetic resonance spectroscopy. The carbon chain of Man was incorporated intact into GXM since13C was observed only in carbon 1 of Man, GlcA, and Xyl. The carbon chain of mannitol was incorporated intact into GXM since13C was observed only in carbons 1 and 6. This was expected since mannitol has an axis of symmetry. The carbon chain of Xyl was identified only in carbons 1 and 3 of Man, GlcA, and Xyl. This pattern of labeling is consistent with the assimilation of Xyl through the pentophosphate pathway.

The polysaccharide capsule of the pathogenic fungus Cryptococcus neoformans enlarges by distal growth and is rearranged during budding

“…To confirm that radioactivity was incorporated into GXM, we incubated the supernatants obtained after the radiation with sepharose conjugated with the mAb to GXM 18B7, and observed that most of the radioactivity was retained by the sepharose matrix (result not shown). This result indicated that most of the radioactive mannose was incorporated into GXM, a finding consistent with previous report that mannose is incorporated directly into GXM (Cherniak et al ., 1998).…”

Cryptococcus neoformans responds to mannitol by increasing capsule size in vitro and in vivo

“…The cryptococcal capsule is composed of two major PSs, glucuronoxylomannan (GXM) and galactoxylomannan (GalXM) (Doering, 2000;Mcfadden et al, 2007;Frases et al, 2008;Villena et al, 2008;Yoneda and Doering, 2008). GXM comprises approximately 90% of the capsule and is formed by a linear (1→3)-a-dmannopyranan main chain bearing b-d-xylopyranosyl (Xyl) in b(1→2) or b(1→4) linkages (Cherniak et al, 1998a), (1→2)b-d-glucopyranosyluronic acid (GlcA) attached to every third mannose, on average, and 6-Oacetyl substituents (Kozel et al, 1988;Cherniak et al, 1998a, Reese andDoering, 2003;Mcfadden et al, 2006a,b;Nimrichter et al, 2007;Frases et al, 2008). GalXM is an a(1→6)-galactan containing b(1, 3) oligosaccharyl substitutions at alternate residues of galactose.…”

Nutritional Requirements and Their Importance for Virulence of Pathogenic Cryptococcus Species

“…Creatinine is not used as a source of carbon by C. neoformans , but is used as a source of nitrogen [ 81 ]. C. neoformans can use xylose, mannose, and mannitol as a sole carbon source [ 82 ]. Cherniak et al used nuclear magnetic resonance spectroscopy (NMR) to study the assimilation of radiolabelled [1-13C]Xyl, [1-13C]Man, and [1-13C]mannitol mannose and their incorporation into capsular glucuronoxylomannan (GXM) [ 82 ].…”

“…C. neoformans can use xylose, mannose, and mannitol as a sole carbon source [ 82 ]. Cherniak et al used nuclear magnetic resonance spectroscopy (NMR) to study the assimilation of radiolabelled [1-13C]Xyl, [1-13C]Man, and [1-13C]mannitol mannose and their incorporation into capsular glucuronoxylomannan (GXM) [ 82 ]. The carbon chains of both mannose and mannitol are incorporated into capsular polysaccharide whilst the carbon chain of xylose was not incorporated intact by the yeast and it was suggested that xylose is assimilated through the pentophosphate pathway (hexose monophosphate shunt).…”