Bacteroidetes use thousands of enzyme combinations to break down glycans.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31053724.
- Also identified by DOI 10.1038/s41467-019-10068-5 and PMC identifier 6499787.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Unlike proteins, glycan chains are not directly encoded by DNA, but by the specificity of the enzymes that assemble them. Theoretical calculations have proposed an astronomical number of possible isomers (> 10<sup>12</sup> hexasaccharides) but the actual diversity of glycan structures in nature is not known. Bacteria of the Bacteroidetes phylum are considered primary degraders of polysaccharides and they are found in all ecosystems investigated. In Bacteroidetes genomes, carbohydrate-degrading enzymes (CAZymes) are arranged in gene clusters termed polysaccharide utilization loci (PULs). The depolymerization of a given complex glycan by Bacteroidetes PULs requires bespoke enzymes; conversely, the enzyme composition in PULs can provide information on the structure of the targeted glycans. Here we group the 13,537 PULs encoded by 964 Bacteroidetes genomes according to their CAZyme composition. We find that collectively Bacteroidetes have elaborated a few thousand enzyme combinations for glycan breakdown, suggesting a global estimate of diversity of glycan structures much smaller than the theoretical one.
Medical subject headings
- Bacterial Proteins
- Bacteroidetes
- Enzymes
- Genome, Bacterial
- Polysaccharides