Non-enzymatic glycosylation influences Hb S polymerization

In vivo glycosylated components of Hb S were isolated from red cell hemolysates of sickle cell anemia patients by application of affinity chromatographic and cation exchange chromatographic techniques. The total glycosylated fraction (GHb) of the whole hemolysate, Hb SIc, Hb So-glycosylated (formed mostly by glycosylation epsilon-NH2 groups of lysyl residues), and Hb So-nonglycosylated fractions were isolated in this manner. GHb contained about 33% Hb SIc and 42% Hb So (Hb So-glycosylated) and the rest was glycosylated Hb F and Hb A2. As expected, the binding of 2,3-DPG was affected only in Hb SIc and not in Hb So-glycosylated. Hb SIc and Hb So-glycosylated had higher solubility in concentrated phosphate solutions and had higher minimum gelling concentrations than the non-glycosylated form of Hb So. These effects are interpreted to be due to modification by glycosylation of specific sites that are directly or indirectly involved in the intermolecular contacts.