Biosynthesis of the cancer-associated sialyl-Lex determinant in human amniotic fluid.

Biosynthesis of the sialyl-Lex determinant (NeuAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)-GlcNAc beta 1-3-R) in human amniotic fluid has been shown to proceed via the same sequence of glycosylation steps established previously for lung carcinoma PC 9 cells (Holmes, E. H., Ostrander, G.K. & Hakomori, S. (1986) J. Biol. Chem. 261, 3737-3743): sialylation of type-2-chain-precursor substrates (paragloboside) by an amniotic alpha 2-3-sialyltransferase precedes fucosylation of sialylated intermediates (sialosyl paragloboside) by an organ-characteristic alpha 1-3-L-fucosyltransferase.