Purification and characterization of secretory-type GDP-L-fucose: beta-D-galactoside 2-alpha-L-fucosyltransferase from human gastric mucosa.

alpha-(1,2)-Fucosyltransferase (GDP-L-fucose:beta-D-galactoside 2-alpha-L-fucosyltransferase) from human gastric mucosa was purified to homogeneity by column chromatographies on Ultrogel AcA34, phenyl-Sepharose, hydroxylapatite, SP-Sephadex, and GDP-hexanol-amine Sepharose. The molecular weight of the purified enzyme was estimated to be 65,000 by SDS-PAGE. The Km value of this enzyme for a type 1 sugar acceptor was a little smaller than that for a type 2 one, indicating this enzyme is a secretor-type alpha-(1,2)-fucosyltransferase. However, the difference between the Km value for a type 1 precursor and that for a type 2 one was very small, suggesting that this enzyme can use both types of precursors as sugar acceptors approximately equally, unlike the purified alpha-(1,2)-fucosyltransferase from human serum as the secretor-type reported previously. The characteristics of the purified enzyme were compared with those of H-type alpha-(1,2)-fucosyltransferase from human plasma. The activities of both enzymes were inhibited by salt and N-ethylmaleimide, but they showed a significant difference in their divalent cation requirements.