Epitamers

Epitomers are a specific type of stereoisomer. When two monosaccharides or other carbohydrates differ in configuration at only one chiral center, they are called epitomers. This is a narrower definition than diastereomers, as epitomers are a subclass of diastereomers. The most common and well-known example of epitomers involves glucose and galactose. These two sugars are epimers because they have identical structures except for the arrangement of the hydroxyl group on the fourth carbon atom.

The epimeric relationship is significant in biological systems. For instance, the interconversion between glucose and its epimer, galactose, is catalyzed by an enzyme called UDP-galactose 4-epimerase. This enzyme is crucial for the synthesis of lactose, the primary sugar in milk. Different carbohydrate structures resulting from epimeric differences can lead to distinct biological functions and recognition patterns. For example, changes in the epimeric form of a sugar moiety on a cell surface can alter cell-cell interactions or how a cell is recognized by the immune system. Therefore, understanding epitomers is important in fields such as biochemistry, organic chemistry, and glycobiology.