Enzymatic basis for the accumulation of glycolipids with X and dimeric X determinants in human lung cancer cells (NCI-H69).

摘要: Abstract Many human carcinomas accumulate a large quantity of glycolipids having X (Gal beta 1----4[Fuc alpha 1----3] GlcNAc) as well di- or trimeric determinant 1----4 [Fuc GlcNAc 1----3Gal 1----3]GlcNAc 1----3Gal) (e.g. Hakomori, S., Nudelman, E., Levery, S. B., and Kannagi, R. (1984) J. Biol. Chem. 259, 4672-4680). The enzymatic basis this phenomenon has been investigated with small cell lung carcinoma NCI-H69 cells, in which series these structures found to accumulate. An 1----3 fucosyltransferase solubilized from the membrane fraction Triton X-100 catalyzed not only transfer fucosyl residue GDP-fucose penultimate lactoneotetraosylceramide (nLc4) lactonorhexaosylceramide (nLc6), but also internal (III-GlcNAc) y2 glycolipid (V3FucnLc6) that sialosyl2----6lactonorhexaosylceramide (VI6NeuAcnLc6). No fucose occurred, unless above substitutions (V3Fuc VI6NeuAc) were present. Fucosylation at V-GlcNAc III-GlcNAc nLc6 could be by same enzyme, based on following observations: (i) fucosylation both III- was competitively inhibited V3FucnLc6 III3V3Fuc2nLc6; (ii) conditions (pH, bivalent cation, detergent) optimal for V-GlcNAc; (iii) Km values enzyme nLc4, nLc6, approximately same; (iv) activity catalyzing adsorbed GDP-hexanolamine-Sepharose N-ethylmaleimide. preferentially transferred VGlcNAc, followed nLc6. Thus, pathway synthesis dimeric proceeds follows: nLc6----V3FucnLc6----III3V3Fuc2nLc6. mechanism operate chain elongation hapten structure through addition residues terminal Gal hapten.