Glycosidase-catalyzed synthesis

Zeng XX, Murata T, Usui T. Glycosidase-catalyzed synthesis of fucosyl di- and trisaccharide derivatives using alpha-L-fucosidase from Alcaligenes sp. J. Carbohydr. Chem. 2003 22 309-316. 

The two main approaches to glycosidase-catalyzed synthesis of glycosidic linkages involve direct reversal of hydrolysis (equilibrium-controlled synthesis) and trapping of a glycosyl-enzyme intermediate (kinetically-controlled process) [217]. 

Kobayashi and coworkers proposed a mechanism for the enzymatic polymerization of 3-D-cellobiosyl fluoride with cellulase following the general accepted mechanism for glycosidase-catalyzed synthesis of glycosides. 

Scheme 5 Novel strategies for glycosidase-catalyzed transglycosylation reactions, (a) Glycosidase-catalyzed synthesis coupled in situ to improve overall yields, (b) Utilization of a 6-0x0 p-nitrophenyl galactose donor as a means to improve the yield, (c) Synthesis of artificial chitin in quantitative yield at a high pH.

Yield of Glycosidase-Catalyzed Synthesis of Oligosaccharides. The yield of glycosidase-catalyzed synthesis depends on a number of parameters such as reaction time, temperature, organic solvent, and substrate concentration. 

This note of caution illustrates that it is important to empirically determine whether the regioselectivities observed in glycosidase-catalyzed synthesis will bear any resemblance to those found in the corresponding hydrolytic reactions. 

VaUvety R, GUI IS Vulfson EN. 1998. AppUcation of enzymes to the synthesis of amino acid-based bola and gemini surfactants. Journal of Surfactants and Detergents 1(2) 177-185. van Rantwijk F, Woudenberg-van Oosterom M Sheldon RA. 1999. Glycosidase-catalyzed synthesis of alkyl glycosides. Journal of Molecular Catalysis B Enzymatic 6(6) 511-532. 

Bacillus circulans P-galactosidase prefers 1,4-glycosidic bond formation and ha been used in the large-scale synthesis of IV-acetyllactosamine (7). Coupled with a oi2,6-sialyltransferase, the disaccharide 7 was converted to the sialyldisaccharide, which is nc longer subject to the glycosidase-catalyzed hydrolysis, thus improving the yield (set experimental section) [35]. 

Glycosidase-catalyzed in vitro polymerizations enabled the synthesis of not only various natural polysaccharides, but also some unnatural polysaccharides, when the substrate monomer is appropriately designed in combination with a selected enzyme. 

Figure 6 Synthesis of lactosamine via glycosidase-catalyzed transgalactosylation reaction.

Two approaches have dominated enzyme-catalyzed saccharide synthesis glyco-syl transferase and glycosidase-catalyzed glycosidic bond formation. The first uses the normal biosynthetic machinery of living organisms. In the second, enzymes that normally catalyze transfer of an enzyme-bound glycosyl residue to water are induced to transfer it instead to a different acceptor. 

Glycosidase-catalyzed glycoside synthesis is quite analogous to protease-catalyzed peptide synthesis. As with proteases, glycosidases may be used under either equilibrium or kinetically controlled conditions for synthetic purposes (Fig. 11.3-... 

Although the equilibrium for glycosidase-catalyzed reactions normally favors hydrolysis, such in vivo factors as rapid utilization of products, or localized high concentrations of substrate, may promote synthesis of oligosaccharides. 

Vocadlo DJ, Withers SG. Glycosidase-catalyzed oligosaccharide synthesis. Carbohydr Chem Biol 2000 2 723-844. 

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