Invited Speaker 7th Modern Solid Phase Peptide Synthesis & Its Applications Symposium 2019

Sialyloligosaccharides of protein surface play important roles in many biological events. In order to evaluate the function of sialyloligosaccharides dependent on glycosylation positions and glycosylation number, we synthesized erythropoietin (EPO) having a homogeneous tri-antennary sialyloligosaccharide at 83 and biantennary sialyloligosaccharides at 24 and 38 positions. 

For the preparation of homogeneous Fmoc-Asn-tri-antennary-sialyloligosaccharide, we examined semisynthesis by use of Fmoc-Asn-biantennary oligosaccharide isolated from egg yolk. Nine chemical conversions yielded tri-antennary biantennary oligosaccharides.¹

We also studied the efficient chemical synthesis of glycopeptides, because the amount of tri-antennary oligosaccharide was a few milligram scales.¹  We step-wisely coupled two peptides at the N and C termini of H₂N-Asn-(oligosaccharide)-COOH. This coupling strategy efficiently converted a valuable Fmoc-Asn-tri-antennary-oligosaccharide into glycopeptide-thioester. All other peptide-thioesters and glycopeptide-thioesters having biantennary sialyloligosaccharides were prepared by Boc-SPPS.

Repetitive native chemical ligation and successful folding protocol²yielded homogeneous EPO having biantennary sialyloligosaccharides at 24, 38 and a triantennary sialylglycan at 83.  In this presentation, we would discuss EPO synthesis and its very potent biological activity.

References:

1. Maki, Y.; Okamoto, R.; Izumi, M.; Murase, T.; Kajihara, Y., Semisynthesis of Intact Complex-Type Triantennary Oligosaccharides from a Biantennary Oligosaccharide Isolated from a Natural Source by Selective Chemical and Enzymatic Glycosylation. J Am Chem Soc 2016,138(10), 3461-8.
   
   
2. Chemical synthesis of erythropoietin glycoforms for insights into the relationship between glycosylation pattern and bioactivity, M. Murakami, et al., 
Science Advances, 2016, DOI: 10.1126/sciadv.1500678