An efficient one-pot multienzyme approach has been developed for the synthesis of structural diverse LacNAc, lactose, and their derivatives including those containing negatively charged 6-O-sulfated GlcNAc and C2-substituted GlcNAc or Glc analogs. Two bacterial β1–4-galactosyltransferases, NmLgtB and Hp1–4GalT, exhibits promiscuous and complementary acceptor substrate specificity. The application of these enzymes in the one-pot multienzyme system allows the access to complex disaccharides with diverse structural modifications from monosaccharide derivatives and inexpensive Glc-1-P without using expensive sugar nucleotide. Bacterial carbohydrate-biosynthetic enzymes have been proven as efficient tools in novel synthesis of diverse and complex carbohydrates.

Aberrant expression of human sialidases has been shown to associate with various pathological conditions. Despite the effort in sialidase inhibitor design, less attention has been paid to designing specific inhibitors against human sialidases and characterizing the substrate specificity of different sialidases regarding diverse terminal sialic acid forms and sialyl linkages. This is mainly due to the lack of sialoside probes and efficient screening methods, as well as limited access to human sialidases. Low cellular expression level of human sialidase NEU2 hampers its functional and inhibitory studies. Here we report the successful cloning and expression of human sialidase NEU2 in E. coli. About 11 mg of soluble active NEU2 was routinely obtained from 1 L of E. coli cell culture. Substrate specificity studies of the recombinant human NEU2 using twenty para-nitrophenol (pNP)-tagged α2–3- or α2–6-linked sialyl galactosides containing different terminal sialic acid forms including common N-acetylneuraminic acid (Neu5Ac), non-human N-glycolylneuraminic acid (Neu5Gc), 2-keto-3-deoxy-D-glycero-D-galacto-nonulosonic acid (Kdn), or their C5-derivatives in a microtiter plate-based high-throughput colorimetric assay identified a unique structural feature specifically recognized by the human NEU2 but not two bacterial sialidases. The results obtained from substrate specificity studies were used to guide the design of a sialidase inhibitor that was selective against human NEU2. The selectivity of the inhibitor was revealed by the comparison of sialidase crystal structures and inhibitor docking studies.

A Pasteurella multocida N-acetylglucosamine 1-phosphate uridylyltransferase (PmGlmU) was cloned and used efficiently with an N-acetylhexosamine 1-kinase (NahK_ATCC55813) and an inorganic pyrophosphatase (PmPpA) for one-pot three-enzyme synthesis of UDP-GlcNAc derivatives with or without further chemical diversification.

Glycosphingolipids are a diverse family of biologically important glycolipids. In addition to variations on the lipid component, more than 300 glycosphingolipid glycans have been characterized. These glycans are directly involved in various molecular recognition events. Several naturally occurring sialic acid forms have been found in sialic acid-containing glycosphingolipids, namely gangliosides. However, ganglioside glycans containing less common sialic acid forms are currently not available. Herein, highly effective one-pot multienzyme (OPME) systems are used in sequential for high-yield and cost-effective production of glycosphingolipid glycans, including those containing different sialic acid forms such as N-acetylneuraminic acid (Neu5Ac), N-glycolylneuraminic acid (Neu5Gc), 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (Kdn), and 8-O-methyl-N-acetylneuraminic acid (Neu5Ac8OMe). A library of 64 structurally distinct glycosphingolipid glycans belonging to ganglio-series, lacto-/neolacto-series, and globo-/isoglobo-series glycosphingolipid glycans is constructed. These glycans are essential standards and invaluable probes for bioassays and biomedical studies.

A novel D-galactosyl-β1–3-N-acetyl-D-hexosamine phosphorylase cloned from Bifidobacterium infantis (BiGalHexNAcP) was used with a recombinant E. coli K-12 galactokinase (GalK) for efficient one-pot two-enzyme synthesis of T antigens, galacto-N-biose (Galβ1–3GalNAc), lacto-N-biose (Galβ1–3GlcNAc), and their derivatives.