earticle

영어

The International Society of Rare monosaccharide (ISRS) defines rare monosaccharides as monosaccharides and their derivatives that rarely exist in nature. Rare monosaccharides have recently gained increasing attention due to their possible applications as low-calorie sweeteners, bulking agents, antioxidants, inhibitors of microbial growth and glycosidases, nucleoside analogues, and immunosuppressants. Generally, rare monosaccharides have been mainly produced by chemical synthesis. However, the chemical processes have many disadvantages, including low overall yield, many reaction steps, complex purification steps, and by-product formation. Because of them, the bio-conversion of rare monosaccharides by enzymes have been recently attracted much attention as one of alternative production methods for rare monosaccharides to overcome these disadvantages. Among various enzymes, enzymes related sugar metabolism such as sugar phosphate isomerases and sugar isomerases have been paid much attention for the bio-conversion of rare monosaccharides because they are involved interconversion of various types of phosphate sugar or monosaccharides in the sugar metabolism. D-ribose-5-phosphate isomerase and D-lyxose isomerase in the enzymes related sugar metabolism have been reported especially useful enzymes to produce rare monosaccharides with their broad substrate specificities. From the study of the substrate specificities of the sugar isomerases, that has been known the configuration of hydroxyl group on the monosaccharides is one of the most important factor on the enzyme activity. The D-ribose-5-phospahte isomerase has enzyme activity for the aldose substrates with the C2 and C3 hydroxyl groups in the right-hand configuration (Fischer projections). In the case of D-lyxose isomerase, the aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration are the most proper substrates. The substrate specificities of the both enzymes could be applied to produce various kinds of rare keto- and aldo-monosaccharides having various biological functions.