ENZYMATIC METHODS IN PREPARATIVE CARBOHYDRATE-CHEMISTRY

This chapter discusses the use of enzymic methods in preparative carbohydrate chemistry. Natural sugars are very active metabolites in cells, and so it can be expected that enzymes are useful at some steps in their in vitro processing. However, enzymes are rare, costly, or need to be isolated by unfamiliar techniques. Coenzymes, which are often necessary, are in most cases complicated and costly molecules and their preparation on a large scale may be exceedingly tedious. An inconvenience of enzymic reactions appears in glycosylation with stoichiometric amounts of “nucleotidesugars.” The result of the coupling reaction is the accumulation, in the medium, of the corresponding free nucleotide that may prove inhibitory to transferases at millimolar concentrations. The now-classical solution to these problems is to attach the enzyme to a suitable polymer that is used as an aqueous suspension. When the reaction is finished, the enzyme is separated from the products by filtration and, not infrequently, may be used again many times. This chapter describes the concepts related to immobilization process. It provides details about aldol additions and other C–C, bond-forming reactions. It also explains the concepts related to phosphorylation and transfer reactions catalyzed by glycosidases. © 1991 Academic Press Inc.