The O-linked fucose glycosylation pathway: identification and characterization of a uridine diphosphoglucose: fucose-beta 1,3-glucosyltransferase activity from Chinese hamster ovary cells

O-Linked fucose is an unusual carbohydrate modification in which fucose is linked directly to the hydroxyl groups of serines or threonines, It has bee n found on the epidermal growth factor-like modules of several secreted pro teins involved in blood coagulation and fibrinolysis, We have recently repo rted the existence of an elongated form of O-linked fucose in Chinese hamst er ovary cells consisting of a glucose linked to the 3'-hydroxyl of fucose (Glc beta 1,3Fuc-O-Ser/Thr). This structure is highly unusual for two reaso ns. First, in mammalian systems fucose is usually a terminal modification o f N- and O-linked oligosaccharides. Here the fucose is internal. Secondly, terminal beta-linked glucose is extremely rare on mammalian glycoconjugates . Thus, the Glc beta 1,3Fuc structure is a very unique mammalian carbohydra te structure. Here we report the identification and initial characterizatio n of a novel enzyme activity capable of forming this unique linkage: UDP-gl ucose: O-linked fucose beta 1,3 glucosyltransferase. The enzyme utilizes UD P-glucose as the high energy donor and transfers glucose to or-linked fucos e residues. The activity is linearly dependent on time, enzyme, and substra te concentrations and is enhanced in the presence of manganese ions. Activi ty is present in extracts of cultured cells from a variety of species (hams ter, human, mouse, rat, chicken) and is enriched in brain and spleen of a n ormal adult rat. Thus, while this glycosyltransferase appears to be widespr ead in biology, it forms a very unique linkage, and it represents the first mammalian enzyme identified capable of elongating fucose.