Fungal α-mannan (α-mannan)

**Fungal α-mannan** is a highly branched polysaccharide forming the outer layer of the fungal cell wall, most studied in *Aspergillus fumigatus*, *Candida albicans*, and *Saccharomyces cerevisiae*. Its structure consists of an α-(1→6)-linked mannose backbone with α-(1→2) and α-(1→3) side chains, often linked to proteins in the case of yeast N-linked mannan[1][3][6]. Specific mannosyltransferases—including Mnn2, Mnn5, Mnn9, Van1, CmsA/Ktr4, and CmsB/Ktr7—are responsible for its assembly; disruptions to these enzymes affect fungal growth and pathogenicity[1][4][5]. α-mannan is recognized by immune cells and serves as a pathogen-associated molecular pattern (PAMP), triggering host responses[6]. Its complexity and central role in cell wall integrity make it an attractive target for therapeutic intervention and drug development[1][2][4][5]. However, chemical diversity between fungal species and similarity to mammalian glycoproteins pose challenges for drug specificity and safety. Detection of galactomannan (and, less commonly, mannan) antigens in patient samples is widely used as a biomarker for diagnosis of invasive fungal infections, although these tests detect galactofuranose and not pure α-mannan[4]. The α-mannan structure is essential for fungal virulence and survival, making mannan biosynthetic enzymes strategic antifungal drug targets.

Other names

fungal-type mannanyeast mannanα-(1→6)-mannancore-mannanfungal-type galactomannan (FTGM, used when the structure includes galactofuran)N-linked mannan

Inhibition of mannosyltransferases leads to disrupted α-mannan biosynthesis, compromising cell wall integrity and fungal survival; Disruption of cell wall structure exposes fungal pathogens to immune responses or other antifungal agents