PURIFICATION, PROPERTIES AND POSSIBLE GENE ASSIGNMENT OF AN ALPHA-1,3-FUCOSYL-TRANSFERASE EXPRESSED IN HUMAN LIVER

alpha 1,3-Fucosyltransferase solubilized from human liver has been pur ified 40 000-fold to apparent homogeneity by a multistage process invo lving cation exchange chromatography on CM-Sephadex, hydrophobic inter action chromatography on Phenyl Sepharose, affinity chromatography on GDP-hexanolamine Sepharose and HPLC gel, exclusion chromatography. The final step gave a major protein peak that co-chromatographed with alp ha 1,3-fucosyltransferase activity and had a specific activity of simi lar to 5-6 mu mol min(-1) mg(-1) and an M(r) similar to 44 000 deduced from SDS-PAGE and HPLC analysis. The purified enzyme readily utilized Gal beta 1-4GlcNAc, NeuAc alpha 2-3Gal beta 1-4G1cNAc and Fuc alpha 1 -2Gal beta 1-4GlcNAc, with a preference for sialylated and fucosylated Type 2 accepters. Fuc alpha 1-2Gal beta 1-4Glc and the Type 1 compoun d Gal beta 1-3GlcNAc were very poor accepters and no incorporation was observed with NeuAc alpha 2-6Gal beta 1-4GlcNAc. A polyclonal antibod y raised against the liver preparation reacted with the homologous enz yme and also with the blood group Lewis gene-associated alpha 1,3/1,4- fucosyltransferase purified from the human A431 epidermoid carcinoma c ell line. No cross reactivity was found with alpha 1,3-fucosyltransfer ase(s) isolated from myeloid cells. Examination by Northern blot analy sis of mRNA from normal liver and from the HepG2 cell line, together w ith a comparison of the specificity pattern of the purified enzyme wit h that reported for the enzyme expressed in mammalian cells transfecte d with the Fuc-TVI cDNA, suggests a provisional identification of Fuc- TVI as the major alpha 1,3-fucosyltransferase gene expressed in human liver.