Engineering gut microbiota-derived enzymes for glycosaminoglycan metabolism: Catalytic mechanisms, diversity, and technologies

Glycosaminoglycans (GAGs) are structurally complex, sulfate-containing polysaccharides that are abundant in animal-derived foods and host tissues, and they are associated with diverse physiological activities. Their gastrointestinal digestion and utilization depend largely on the enzymatic repertoire of the gut microbiota, which has stimulated growing interest in the mechanisms underlying microbial GAG metabolism. In this context, enzyme engineering is expanding the analytical and biotechnological applications of these enzymes, ranging from GAG disaccharide composition analysis to the preparation of therapeutic GAG-derived oligosaccharides. This review focuses on two key enzymes that govern gut microbial GAG metabolism, polysaccharide lyases (PLs) and sulfatases. We summarize their catalytic mechanisms, substrate specificities, and roles in metabolic pathways. Particular attention is given to structural and functional variations within PL families and S1 sulfatase subfamilies identified in gut microbiota. Recent studies have increasingly revealed enzymes with substrate-specific catalytic properties and gut-adapted functionalities, which in turn provide a mechanistic basis for their rational engineering and targeted design. Overall, these findings underscore the importance of systematic enzymology informing enzyme-engineering strategies and provide new avenues for the selective transformation of dietary sulfated glycans and for the biotechnological production of functional oligosaccharides.