Effects of endogenous soluble beta-galactoside binding lectins and protein inhibitor of fucosyltransferase on the enzymes involved in the intestinal fucosylation process.

Département de Biochimie Générale et Médicale, INSERM 189 alliée au CNRS, Faculté de Médecine Lyon-Sud, Oullins, France.

Soluble beta-galactoside binding lectins were prepared from the rat small intestinal mucosa by chromatography on asialofetuin-Sepharose. The lectin fraction exhibits 3 bands with Mr of 21,5 kDa, 19 kDa and 17 kDa on SDS-PAGE. This fraction inhibits a partially purified soluble alpha(1-2)-fucosyltransferase by interaction with the glycoprotein substrate asialofetuin, whereas the inhibition is non competitive for the donor GDP-fucose. It has no effect on other enzymes of the fucosylation system, namely glycosyl-nucleotide pyrophosphatase and the system synthesizing GDP-fucose from GDP-mannose. A different and specific soluble protein inhibitor of fucosyltransferase activity inhibits this activity by a competitive mechanism for GDP-fucose and a non competitive one for asialofetuin. Unlike the lectins, this inhibitor also inhibits the action of pyrophosphatase and the formation of GDP-fucose by different mechanisms. The possible extension of these in vitro results to the in vivo regulation of glycosylation is discussed.

PMID: 1610354 [PubMed - indexed for MEDLINE]