ABSTRACT
Enzymes are being recognized as efficient catalysts for many of the stereospecific and regioselective reactions necessary for carbohydrate synthesis [l-4]. Thus, natural and cloned glycosyltransferases are now being used in oligosaccharide synthesis, whereas aldolases belonging to the class of lyases have been applied in preparative synthesis of common monosaccharides and analogues. These enzymes, which have mostly catabolic function in vivo, catalyze reversible stereoselective aldol reactions between a nucleophilic donor and an electrophilic acceptor. Excluding deoxyribose aldolase that catalyzes aldol condensation between two aldehydes [5], aldolases can be classified into three major classes, according to the type of donor substrate required: pyruvate-dependent, phosphoenolpyruvate-dependent, and dihydroxyacetone phosphate-dependent lyases. The latter class has been extensively investigated; the most widely used enzyme is fructose diphosphate aldolase (FDPA), which catalyzes the reversible aldol addition of dihydroxyacetone
phosphate (DHAP) and o-glyceraldehyde-3-phosphate to form 1,6-diphosphate fructose, thus creating a new C3-C4 bond with o-threo stereochemistry (Scheme 1) [6].
