REDUCTIVE AMINATION OF N-LINKED OLIGOSACCHARIDES USING ORGANIC-ACID CATALYSTS

The reductive amination of oligosaccharides with 8-aminopyrene-1,3,6-t risulfonate in several organic acids of varying strength was examined by capillary electrophoresis using laser-induced fluorescence detectio n. The relationship between the derivatization yield and the pK(a) of the catalyst (organic acids) is in agreement with the general acid cat alysis of the hemiacetal ring opening and the Shiff base formation, on e of which is considered to be the rate-determining step of the reduct ive amination reaction. Derivatization in the presence of organic acid s having higher acidity than acetic acid, the most commonly used catal yst, resulted in significantly higher derivatization yield and the hig hest yield was attained with the use of citric or malic acid as cataly sts. This effect was even more prominent for oligosaccharides having N -acetylglucosamine at the reducing end compared to the similar size li near glucose oligomers. Sialylated oligosaccharides were derivatized a t 37 degrees C for 16 h with only less than 10% loss of the sialic aci d residues. The derivatization procedures were tested on the N-linked oligosaccharides released enzymatically (peptide-N-glycanase F) from b ovine fetuin and ribonuclease B.