Characterization of a novel pyruvylated carbohydrate unit implicated in the cell aggregation of the marine sponge Microciona prolifera

The species-specific Ca(2+)-dependent reaggregation of dissociated cells of the marine sponge Microciona prolifera is mediated by a large extracellular adhesion proteoglycan. The glycans of this molecule are involved in the interactions of the proteoglycan with itself and with the sponge cells. Monoclonal antibodies against the glycans block the aggregation of sponge cells (Misevic, G. N., Finne, J., and Burger, M. M. (1987) J. Biol. Chem. 262, 5870-5877). Proteoglycan oligosaccharides were prepared by partial acid hydrolysis of the isolated glycans, and their reactivity with the monoclonal antibodies was monitored after linkage to phospholipid and immunostaining of thin layer chromatograms. One major antibody-reactive oligosaccharide was detected and purified by ion-exchange chromatography and high performance liquid chromatography. 1H NMR spectroscopy, fast atom bombardment-mass spectrometry, methylation analysis, and sequential chemical and enzymatic degradation studies indicated the structure [formula: see text] for the oligosaccharide. The depyruvylated derivative of the oligosaccharide did not react with the aggregation-blocking antibody, which indicates that the pyruvate acetal is an essential part of the epitope.