Reductive amination of N-linked oligosaccharides using organic acid catalysts

Abstract

The reductive amination of oligosaccharides with 8-aminopyrene-1,3,6-trisulfonate in several organic acids of varying strength was examined by capillary electrophoresis using laser-induced fluorescence detection. The relationship between the derivatization yield and the p K a of the catalyst (organic acids) is in agreement with the general acid catalysis of the hemiacetal ring opening and the Shiff base formation, one of which is considered to be the rate-determining step of the reductive amination reaction. Derivatization in the presence of organic acids having higher acidity than acetic acid, the most commonly used catalyst, resulted in significantly higher derivatization yield and the highest yield was attained with the use of citric or malic acid as catalysts. This effect was even more prominent for oligosaccharides having N-acetylglucosamine at the reducing end compared to the similar size linear glucose oligomers. Sialylated oligosaccharides were derivatized at 37°C for 16 h with only less than 10% loss of the sialic acid residues. The derivatization procedures were tested on the N-linked oligosaccharides released enzymatically (peptide-N-glycanase F) from bovine fetuin and ribonuclease B.