Synthesis of Neuraminidase‐Resistant Sialyllactose Mimetics from N‐Acyl Mannosamines using Metabolically Engineered Escherichia coli

Abstract

Herein, we describe the efficient gram‐scale synthesis of α2,3‐ and α2,6‐sialyllactose oligosaccharides as well as mimetics from N‐acyl mannosamines and lactose in metabolically engineered bacterial cells grown at high cell density. We designed new Escherichia coli strains co‐expressing sialic acid synthase and N‐acylneuraminate cytidylyltransferase from Campylobacter jejuni together with the α2,3‐sialyltransferase from Neisseria meningitidis or the α2,6‐sialyltransferase from Photobacterium sp. JT‐ISH‐224. Using their mannose transporter, these new strains actively internalized N‐acetylmannosamine (ManNAc) and its N‐propanoyl (N‐Prop), N‐butanoyl (N‐But) and N‐phenylacetyl (N‐PhAc) analogs and converted them into the corresponding sialylated oligosaccharides, with overall yields between 10 % and 39 % (200‐700 mg.L−1 of culture). The three α2,6‐sialyllactose analogs showed similar binding affinity for Sambucus nigra SNA−I lectin as for the natural oligosaccharide. They also proved to be stable competitive inhibitors of Vibrio cholerae neuraminidase. These N‐acyl sialosides therefore hold promise for the development of anti‐adhesion therapy against influenza viral infections.