α-mannan, fungal cell wall

**α-mannan** is a structural polysaccharide forming a major component of the outer layer of many fungal cell walls. It consists of repeating α-linked mannose residues (often α-1,6 and α-1,2 linkages) and may serve as a backbone for large, branched mannans, including galactomannan in *Aspergillus* species[2][4][5][6]. In yeasts like *Saccharomyces cerevisiae* and *Candida albicans*, α-mannan is typically highly branched and linked to glycoproteins, whereas in pathogenic molds like *Aspergillus fumigatus*, it forms part of more linear and complex glycans covalently bound to the glucan–chitin core of the cell wall[2][5]. α-mannan is critical for maintaining cell wall integrity, proper morphogenesis, and virulence of fungal pathogens. Its biosynthesis involves multiple mannosyltransferase enzymes; genetic disruption of these enzymes impairs fungal growth and reduces virulence, underscoring its value as an antifungal target[4]. Clinically, α-mannan (and related galactomannan) is released during invasive fungal infection and serves as a diagnostic biomarker, detectable in patient serum or urine by immunological assays[6]. Current antifungal drugs do not directly target α-mannan, but its biosynthetic enzymes (including core-mannan synthase) represent an active area of therapeutic investigation due to their essential roles and fungal specificity[4][6]. There are no major safety concerns for targeting α-mannan because it is not present in human cells, but diagnostic applications face limitations from biological variability. **Note:** α-mannan is not a classical receptor, ion channel, or enzyme, but a structural carbohydrate; its "target" status comes from its essential biological role and druggability of its biosynthetic enzymes. Also, galactomannan and other related mannans should not be conflated but are often measured or discussed together due to immunological cross-reactivity in diagnostics.

Other names

alpha-mannanfungal α-mannanmannan (fungal)fungal cell wall α-mannangalactomannan (related, but not identical)FTGM (fungal-type galactomannan; contains α-mannan core)

- Disruption of α-mannan biosynthesis (e.g., via inhibition of mannosyltransferases) leads to compromised wall integrity and fungal cell death or reduced virulence[4] - Immunological targeting for diagnostic and therapeutic use (e.g., antibody recognition of shed mannan in fluids)[6]