The human sialyltransferase family

The human genome encodes probably more than 20 different sialyltransferases involved in the biosynthesis of sialylated glycoproteins and glycolipids but to date only 15 different human sialyltransferase cDNAs have been cloned and characterized. Each of the sialyltransferase genes is differentially expressed in a tissue-, cell type-, and stage-specific manner to regulate the sialylation pattern of cells. These enzymes differ in their substrate specificity, tissue distribution and various biochemical parameters. However, enzymatic analysis conducted in vitro with recombinant enzyme revealed that one linkage can be synthesized by multiple enzymes. We present here an overview of these human genes and enzymes, the regulation of their occurrence and their involvement in several physiological and pathological processes.