The glycan alphabet is not universal: a hypothesis

Area of Science:

• Biochemistry
• Genomics
• Evolutionary Biology

Background:

• Naturally occurring glycans are composed of various monosaccharides.
• The universality of the monosaccharide set, analogous to protein and DNA alphabets, remains uncertain.

Purpose of the Study:

• To investigate the hypothesis that the glycan alphabet is not universal.
• To analyze the presence and variation of monosaccharide biosynthesis pathways across archaeal and bacterial genomes.

Main Methods:

• Bioinformatic analysis of 12,939 complete archaeal and bacterial genomes.
• Identification of monosaccharide biosynthesis pathway enzymes through homolog searches.
• Classification of monosaccharides into common, less common, and rare groups based on prevalence.

Main Results:

• Observed substantial variations in monosaccharide sets even within the same species.
• Identified a 'common' group of monosaccharides likely originating before the three domains of life.
• Found 'rare' monosaccharides confined to specific species, suggesting later evolution possibly through gene neo- and sub-functionalization.

Conclusions:

• The glycan alphabet is not universal, with significant diversity in monosaccharide composition.
• Common monosaccharides have ancient origins, while rare ones evolved later.
• The non-universality raises questions about the role of specific monosaccharides in organismal fitness.