A high pH anion exchange chromatographic (HPAEC) system for the separation of isomeric sialo-oligosaccharide products was developed. Employing this system, using Galβ1→4GlcNAcβ1→2Manα1→6Manβ1→4GlcNAc as a substrate, a Galβ1→4GlcNAc-R α2→3-sialyltransferase activity was detected for the first time in human liver. This activity is expressed together with the prevalent α2→6-sialyltransferase. Furthermore, in addition to the major α2→3-sialyltransferase, a low but distinct activity of α2→6-sialyltransferase was detected in human placenta. This activity could not be found by methods based on methylation analysis or high resolution NMR spectroscopy. It is concluded that HPAEC, in combination with the use of the pentasaccharide as an acceptor substrate, is suited for the specific detection of minor, Galβ1→4GlcNAc-specific sialyltransferase activities.
