Analysis of monosaccharides in bovine, caprine and ovine κ-casein macropeptide by gas chromatography

Mammalian sialyltransferase ST3Gal-II: its exchange sialylation catalytic properties allow labeling of sialyl residues in mucin-type sialylated glycoproteins and specific gangliosides

While glycosyltransferases are known to display unidirectional enzymatic activity, recent studies suggest that some can also catalyze readily reversible reactions. Recently, we found that mammalian sialyltransferase ST3Gal-II can catalyze the formation of CMP-NeuAc from 5'-CMP in the presence of a donor containing the NeuAcα2,3Galβ1,3GalNAc unit [Chandrasekaran, E. V., et al. (2008) Biochemistry 47, 320-330]. This study shows by using [9-(3)H]- or [(14)C]sialyl mucin core 2 compounds that ST3Gal-II exchanges sialyl residues between CMP-NeuAc and the NeuAcα2,3Galβ1,3GalNAc unit and also radiolabels sialyl residues in gangliosides GD1a and GT1b, but not GM1. Exchange sialylation proceeds with relative ease, which is evident from the following. (a) Radiolabeleling of fetuin was ~2-fold stronger than that of asialo fetuin when CMP- [9-(3)H]NeuAc was generated in situ from 5'-CMP and [9-(3)H]NeuAcα2,3Galβ1,3GalNAcβ1,3Galα-O-Me by ST3Gal-II. (b) ST3Gal-II exchanged radiolabels between [(14)C]sialyl fetuin and [9-(3)H]NeuAcα2,3Galβ1,3GalNAcβ1,3Galα-O-Me by generating CMP-[(14)C]- and -[9-(3)H]NeuAc through 5'-CMP; only 20.3% (14)C and 28.0% (3)H remained with the parent compounds after the sialyl exchange. The [9-(3)H]sialyl-tagged MN glycophorin A, human chorionic gonadotropin β subunit, GlyCAM-1, CD43, fetuin, porcine Cowper's gland mucin, bovine casein macroglycopeptide, human placental glycoproteins, and haptoglobin were analyzed by using Pronase digestion, mild alkaline borohydride treatment, Biogel P6, lectin agarose, and silica gel thin layer chromatography. Sulfated and sialylated O-glycans were found in GlyCAM-1 and human placental glycoproteins. This technique has the potential to serve as an important tool as it provides a natural tag for the chemical and functional characterization of O-glycan-bearing glycoproteins.

Derivatization of carbohydrates for GC and GC-MS analyses

GC and GC-MS are excellent techniques for the analysis of carbohydrates; nevertheless the preparation of adequate derivatives is necessary. The different functional groups that can be found and the diversity of samples require specific methods. This review aims to collect the most important methodologies currently used, either published as new procedures or as new applications, for the analysis of carbohydrates. A high diversity of compounds with diverse functionalities has been selected: neutral carbohydrates (saccharides and polyalcohols), sugar acids, amino and iminosugars, polysaccharides, glycosides, glycoconjugates, anhydrosugars, difructose anhydrides and products resulting of Maillard reaction (osuloses, Amadori compounds). Chiral analysis has also been considered, describing the use of diastereomers and derivatives to be eluted on chiral stationary phases.