(A) A dansylated glycopeptide (dansyl-Asn-Ser-Man5GlcNAc2; Man5) was incubated in the presence of (1) a lysate of mid-log phase Dictyostelium AX3 cells and GDP-Fuc, (2) an AX3 lysate without GDP-Fuc, (3) an HL250 lysate and GDP-Fuc, (4) purified recombinant Caenorhabditis elegans FUT-1 and GDP-Fuc or (5) no enzyme. The shift to a lower retention time results in formation of a fucosylated glycopeptide (Man5Fuc). (B) The collected Man5Fuc fraction was subject to MALDI-TOF MS verifying the addition of fucose (m/z [M+Na]+ = 1837; as compared to the non-fucosylated from with m/z 1691). (C) The core 1,3-linkage of the transferred fucose was demonstrated by the presence of 3,4-disubstituted GlcNAc (2-deoxy-2-(N-methyl)acetamido-6-O-methyl-glucitol) in the obtained EI spectrum.