N-Acetyl-D-glucosamine-specific lectin from the ascidian Didemnum ternatanum.

We report the characterization of the affinity chromatography-purified N-acetyl-d-glucosamine-specific lectin from the ascidian Didemnum ternatanum (DTL). Native molecular weight of lectin estimated by gel filtration was 28 000. The hemagglutinating activity of DTL independent of divalent cations Ca2+ and Mg2+. Significant activity was observed between pH 6-10. In hemagglutination inhibition assays among the mono- and oligosaccharides tested, N-acetyl-d-glucosamine, N, N'-diacetylchitobiose, N,N'N"-triacetylchitotriose were the most potent inhibitors. They showed similar inhibitory activity. Hapten inhibition with various sugars indicated that DTL requires the presence of hydroxyl groups at the C-3 and C-4 of N-acetyl-d-glucosamine. The presence of the hydrophobic p-nitrophenyl aglycone significantly enhanced inhibitory power of N-acetyl-d-glucosamine. On the other hand among the glycoproteins ovomucoid and ovalbumin were the best inhibitors. The interaction of DTL with specific saccharides was investigated by UV difference spectroscopy and association constants were obtained. CD analysis of DTL suggested 4% alpha-helix, 57% beta-sheet, 24% beta-turn and 15% unorder. Copyright 1998 Elsevier Science B.V.