Expression of Specific Carbohydrates by Transfection with Carbohydrate Modifying Enzymes

The identification of cDNAs encoding glycosyltransferases and carbohydrate‐modifying enzymes such as sulfotransferases has allowed expression of a given enzyme in cells that lack the enzyme or express it at very low levels. By comparing the function and/or structure of carbohydrates expressed in cells before and after transfection, we can determine the function of the ectopically expressed enzyme. This assay is less time consuming than assaying function by obtaining cells deficient in a given enzyme. Moreover, it is a more definitive method for establishing the function of the enzyme because the result is derived from an enzyme introduced by transfection. Using this method, an enormous amount of knowledge relevant to the structure and function of glycoenzymes has been derived from such studies. In this chapter, we describe methods used to obtain mammalian cells that have acquired new carbohydrate structures and function following transfection of mammalian expression vectors harboring glycoenzymes.