Diversity and ecological roles of alginate lyases in marine and human microbial ecosystems

Acidic polysaccharides such as alginate, a key component of brown algae, have unique properties conferred by their carboxyl groups. Alginate is degraded by alginate lyases, a class of polysaccharide lyases (PLs) that cleave uronic acid glycoside bonds via β-elimination. These enzymes, which are classified into various PL families, differ in structure and substrate specificity but frequently share structural motifs including β-helices, β-jelly rolls, and (α/α)6 barrels coupled with antiparallel β-sheets. Moreover, marine bacteria from the genera Alteromonas, Pseudoalteromonas, and Vibrio produce alginate lyases that belong to several PL families that are associated with blue carbon cycling. Furthermore, some Bacteroides species in the human gut have acquired alginate-degrading genes via horizontal transfer from marine bacteria and/or other Bacteroides species. Alginate fermentation by gut microbes can produce short-chain fatty acids with potential prebiotic effects. This review explores alginate lyase diversity, ecological roles, and relevance in both marine and human microbial ecosystems.