FIGURE 7.

IC₅₀ values for recognition of a small panel of sialosides by human and murine CD22. A, scheme for the chemoenzymatic synthesis of four representative glycans used for probing the ligand specificity of human and murine CD22. LacNAc or its 6-O-sulfate-modified derivative was coupled to either Neu5Ac or Neu5Gc in an α2–6-linked glycosidic linkage using the human ST6Gal1 enzyme. The source of Neu5Ac and Neu5Gc was from ManNAc and N-glycolylmannosamine, respectively, using the aldolase N. meningitides sialic acid synthetase (NmCSS) in a coupled reaction with the sialyltransferase ST6Gal1. B, binding affinity of the four chemo-enzymatically synthesized trisaccharides was determined by a competitive bead binding assay with human and murine CD22. Values represent the mean and standard deviations for four independent experiments.