Enzymatic Synthesis Of Fucosylated Human Milk Oligosaccharides

Human milk oligosaccharides(HMOs)are the third most abundant solid component in human milk following lactose and lipids.All the HMOs share the same lactose core at the reducing end.The core lactose can be enzymatically elongated by the type 1 disaccharide(Gal?1-3GlcNAc)to give the lacto-N-tetrasaccharide(LNT)or by type 2 disaccharide(Gal?1-4GlcNAc)to afford the lacto-N-neotetrasacchride(LNnT).The LNT and LNnT can be further branched or elongated to generate more than 10 core structures,and these core structures can be further modified by sialylation and/or fucosylation at various sites to afford over 100 distinct HMOs.The fucosylated HMOs are the most common structures of known HMOs.It has been well established that the fucosylated HMOs play very important roles in many biological processes.For example,the fucosylated HMOs are prebiotics which can shape the microbiota in gut.They can also act as soluble decoy receptors to block pathogens from attaching to host cells.Despite their important roles,the synthesis of these diverse HMOs is still very challenging.To tackle this problem,a highly efficient enzymatic modular assembly strategy was developed in this study.Seven enzyme modules were designed and successfully applied to the synthesis of twelve fucosylated HMOs via sequential glycosylation,and 11 complex oligosaccharides were synthesized for the first time.This robust enzymatic approach provides an easy access to various fucosylated HMOs,which could be valuable tools for detail biological studies.