Site-specific glycosylation of human recombinant erythropoietin: analysis of glycopeptides or peptides at each glycosylation site by fast atom bombardment-mass spectrometry

We have previously determined the carbohydrate structure of human recombinant erythropoietin [Sasaki, H., Bothner, B., Dell, A., (2) saccharides at Asn38 mainly consist of well-processed saccharides such as tetraantennary saccharides with or without N-acetyllactosaminyl repeats; (3) saccharides at Asn83, on the other hand, are homogeneous in the backbone structure and are composed mainly of tetraantennary without N-acetyllactosaminyl repeats. It was also noted that saccharides at Asn24 are much less sialylated than those at Asn38, although these two glycosylation sites are close to each other. These results clearly indicate that the protein structure and, possibly, the carbohydrate chain at the neighboring site greatly influence glycosylation of a given glycosylation site.