Tetsuya Kajimoto

Azasugar and glycal inhibitors of α-L-fucosidase

Abstract Several azasugar and glycal inhibitors were studied to map the active site of α-L-fucosidase enzyme.

Enzymes for carbohydrate and peptide syntheses

New practical procedures have been developed for the enzyme-catalyzed synthesis of carbohydrates and peptides. Aldolases have been shown to be effective catalysts for the synthesis of uncommon sugars, particularly azasugars. Enzymatic methods for the large-scale synthesis of oligosaccharides have been developed with the use of glycosyltransferases coupled with the regeneration of sugar nucleotides. Engineered subtilisin variants that are stable and active in anhydrous dimethylformamide and in aqueous solution have been developed for peptide segment coupling.

Practical synthesis of carbohydrates based on aldolases and glycosyl transferases

With various recombinant DNA and protein engineering techniques now available, enzyme-bad technologies are emerging as practical methods for large-scale synthesis of chiral intermediates and bioactive molecules, especially carbohydrates, oligosaccharides, their conjugates and related substances. This paper describes recent developments in the synthesis of novel monosaccharides and aza sugars based on aldolases, and the synthesis of oligosaccharides and analogs based on glycosyltransferases coupled with in sins regeneration of sugar nucleotides. As many enzymes are available for the stereocontrolled synthesis of chiral synthons (l), attention has been extended to the development of more effective and stable enzymes for the synthesis of molecules with increasing complexity (2). One class of such complex molecules are carbohydrates and their conjugates, especially those that exist on cell surfaces (3). These molecules are involved in many types of recognition phenomena (3-6); however, most of their precise functions have not been clearly identified at the molecular level. Part of the reason is that these molecules have been difficult to isolate, characterize and synthesize. Enzyme-based technology seems to be well suited for the synthesis of glycoconjugates and related substances for the study of their functions as these molecules are multifunctional and highly soluble in polar solvents, and many enzymes are available for the transformation of these molecules (7). The following describes some new technologies developed for the synthesis of sugar- and peptide- related substances based on recombinant or engineered enzymes.

Chemical-Enzymatic Synthesis of Carbohydrates

This paper describes the use of three types of enzymes in carbohydrate synthesis. Aldolases are a useful class of catalysts for the synthesis of aza sugars and related compounds. Glycosyltransferases have been developed for the synthesis of oligosaccharides. The enzymatic oligosaccharide synthesis has been proven effective and practical when coupled with in situ regeneration of sugar nucleotides. A subtilisin variant prepared via site-directed mutagenesis is stable and active in dimethylformamide and is useful for regioselective acylation of sugars.

Developing better enzymes for organic synthesis.

Glycoconjugates that exist on cell surfaces are involved in many types of biochemical recognitions. These molecules have been difficult to isolate, characterize, and synthesize, and are the least explored of the major classes of biomolecules. Carbohydrate-related structures therefore offer opportunities for the study of molecular recognition and for the development of therapeutic agents. The recently identified tetrasaccharide sialyl Lewis x, as the ligand of the endothelial leukocyte adhesion molecule,* stimulates new interests in the development of practical methods for the synthesis of carbohydrates and mimetics as ligands or antagonists of carbohydratebinding proteins, or as inhibitors of specific glycoenzymes such as glycosidases and glycosyltransferases. Our interest in this area is to develop enzyme-based technology for the synthesis of carbohydrates and related substances, to make these materials readily available to study their structure-function relation, and to evaluate their therapeutic potential.