Identification and characterization of an o-linked fucose-specific β 1,3-glucosyltransferase activity from chinese hamster ovary cells

O-linked fucose refers to the post-translational modification where the sugar, fucose, is attached directly to protein on serines and threonines. This unique modification has been found on the epidermal growth factor-like domains of several secreted proteins involved in blood coagulation and fibrinolysis. Typ ically in mammalian systems, fucose is found as a terminal sugar on both Nand O-linked carbohydrates. However, we have observed a distincl form of Olinked fucose on Chinese hamster ovary proteins where fucose is elongated by a 3 1.3-glucose residue. Here, we show the identification and characterization of a novel enzyme activity which is responsible for the addition of the glucose residue to O-linked fucose. The activity is linearly dependent on time, enzyme. and substrate concentration. The enzyme utilizes UDP-glucose and transfers glucose only to alpha-linked fucose. Like many typical ER/golgi glycosyltransferases, there is an enhancement of activity in the presence of manganese ions. This novel glucosyltransferase activity was observed in cultured relis from a variety of species (hamster, human, mouse, rat, and chicken), and activity was found to be enriched in brain, heart, and spleen of a normal adult rat. This work was supported by NIH grant GM48666.