Active oligosaccharides enzymatic synthesis

On the other hand, the enzymatic synthesis of glycoconjugates and oligosaccharides leads to high product yields in a short time by stereo- and regioselective one-step reactions. All enzymatic reactions are easy to scale up and are carried out in aqueous media under mild conditions. A whole set of enzymes is now available to build up OAT bonds in monosaccharides, COP bonds in activated monosaccharides e.g. phosphorylated sugars or nucleotide sugars, and C-O-C bonds in di- and oligosaccharides (Fig. 1). However, all these enzymatic reactions are limited by the substrate spectrum of the individual enzyme. 

The low cost of sucrose makes it an attractive synthetic precursor for a wide range of applications (56), and a chlorinated derivative (l,6-dichloro-6-deoxy-(3-D-fructofuranosyl 6-chloro-4,6-dideoxy-a-D-galactopyranoside, sucralose) is widely used as a noncaloric sweetener (Splenda ). Various other oligosaccharides occur naturally in the free form (57), but far more have been isolated as fragmentation products from larger biomolecules their chemical or enzymatic synthesis is a very active current area of research, as detailed in Chapters 3 and 4. 

Polyphosphate kinase has been found able to phosphorylate nucleoside diphosphates to give nucleoside triphosphates, using PolyP as a phosphate donor. Therefore, the possibility of using PolyP and polyphosphate kinase instead of phosphoenol pyruvate and pyruvate kinase for enzymatic oligosaccharide synthesis was examined, because PolyP is quite cheap when compared with phosphoenol pyruvate (Noguchi and Shiba, 1998 Shiba et al, 2000). Attempts were made to synthesize N-acetyllactosamine (Gal (f> 1-4) GlcNAc) using the nucleoside diphosphate kinase-like activity of polyphosphate kinase, where UDP-Glc pyrophosphorylase and UDP-Glc 4-epimerase catalyse the synthesis of UDP-Glc from... 

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