Glucuronyltransferases Involved in the HNK-1 Carbohydrate Epitope Biosynthesis

Over the past decade glucuronyltransferases (GlcATs) involved in the biosynthesis of the HNK-1 carbohydrate epitope have been identified and cloned successively. The structure of the HNK-1 carbohydrate epitope is characterized by terminal sulfated glucuronic acid, and GlcATs are thought to be the key enzyme in the biosynthesis pathway of this epitope. Following isolation of several GlcAT cDNAs, structural comparison of GlcATs has proposed a new glucuronyltransferase family characterized by four conserved modules in the catalytic region. In mammals GlcAT-P and GlcAT-S are involved in the biosynthesis of the HNK-1 epitope, and their expression were mainly localized in the neural tissues. These two enzymes however expressed in the different region of the neural tissues and exhibit different acceptor specificity. Cloned cDNAs of these GlcATs are able to induce expression of the HNK-1 epitope on the surface of HNK-1 negative cells. GlcATs are powerful tools for investigating the biological function of the HNK-1 carbohydrate epitope.