The Chinese hamster ovary glycosylation mutants LEC11 and LEC12 express two novel GDP-fucose:N-acetylglucosaminide 3-alpha-L-fucosyltransferase enzymes.

Evidence is presented that the GDP-fucose:N-acetyl-glucosaminide 3-alpha-L-fucosyltransferase activities of two Chinese hamster ovary glycosylation mutants, LEC11 and LEC12, are structurally distinct enzymes. The alpha(1,3)fucosyltransferase in LEC12 cell extracts binds to GDP-hexanolamine-Sepharose and is unaffected by 3 mM N-ethylmaleimide. In contrast, the alpha(1,3)fucosyltransferase activity in LEC11 cells does not bind readily to GDP-hexanolamine-Sepharose and is completely inhibited by 1 mM N-ethylmaleimide. The LEC11 and LEC12 alpha(1,3)fucosyltransferases also differ in the degree to which they are stimulated by divalent cations as well as in their abilities to fucosylate a variety of exogenous substrates. Of particular interest is the finding that the LEC11 alpha(1,3)fucosyltransferase adds fucose to certain sialylated glycoproteins, whereas the LEC12 enzyme is essentially unable to fucosylate these acceptors, although it is very active with their desialylated derivatives. The combined evidence shows that the LEC11 and LEC12 alpha(1,3)fucosyltransferase enzymes are different molecules and presumably, therefore, the products of distinct genes. In addition, neither of the enzymes appears identical to any of the previously described alpha(1,3)fucosyltransferase activities from other sources.