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Abstract
Human milk oligosaccharides (HMOs) are structurally diversified carbohydrates rich in the breast milk. They are the third largest component of human milk following lactose and lipids. Decades ago, these components were thought to play a role only as nutrient for intestinal microbiota with health benefits. With growing research into HMOs, they are found to exert additional beneficial properties. The structural similarities between cell surface glycans and HMOs enable pathogen recognition, preventing bacterial from attaching the epithelial cell surface. Although the biological function has been elucidated, multiple cases of breast-fed infants were observed to develop diarrhea in different stage of lactation. Whether variation in the HMO composition accounts for the loss of protective factors remains to be established.
To establish an integrated system of understanding functional and metabolic properties of individual HMOs, accessing well-defined structures is crucial. To address this challenge, chemo-enzymatic strategies have been developed to realize efficient synthetic strategy. For the first time a panel of defined HMOs are built with type I structure on β3 branch, displaying asymmetry and highly complex glycol-epitopes proposed to be baits for glycan-binding proteins. Extensions of HMOs was achieved by engaging a range of glycosyl transferases based on specific regio- and stereo- selectivity. With the growing interest in how fucosylation patterns maneuver binding affinity, the substrate specificities of diverse FUTs (fucosyltransferases) have been thoroughly investigated on type I structures, elucidating the synthetic potential and limitation of such enzyme category. The modular enzymatic synthesis delineates patterns of substrates glycosyltransferases recognize, supplementing information of biosynthetic pathway of complex HMOs.
Our synthetic strategy was fulfilled with an auxiliary anomeric linker which could be used in HPLC purification and potential microarray printing. The linker is composed of a coumarin functional group which gives UV signal for HPLC purification and hydrophobicity, a lysine chain allowing the conjugated glycan to be mobilized on glass slides for subsequent microarray analysis.
To establish an integrated system of understanding functional and metabolic properties of individual HMOs, accessing well-defined structures is crucial. To address this challenge, chemo-enzymatic strategies have been developed to realize efficient synthetic strategy. For the first time a panel of defined HMOs are built with type I structure on β3 branch, displaying asymmetry and highly complex glycol-epitopes proposed to be baits for glycan-binding proteins. Extensions of HMOs was achieved by engaging a range of glycosyl transferases based on specific regio- and stereo- selectivity. With the growing interest in how fucosylation patterns maneuver binding affinity, the substrate specificities of diverse FUTs (fucosyltransferases) have been thoroughly investigated on type I structures, elucidating the synthetic potential and limitation of such enzyme category. The modular enzymatic synthesis delineates patterns of substrates glycosyltransferases recognize, supplementing information of biosynthetic pathway of complex HMOs.
Our synthetic strategy was fulfilled with an auxiliary anomeric linker which could be used in HPLC purification and potential microarray printing. The linker is composed of a coumarin functional group which gives UV signal for HPLC purification and hydrophobicity, a lysine chain allowing the conjugated glycan to be mobilized on glass slides for subsequent microarray analysis.