beta-Phosphorothioate analogs of nucleotide sugars are resistant to hydrolytic degradation and utilized efficiently by glycosyltransferases

A chemoenzymatic synthesis of UDP-(2-deoxy-2-fluoro)-galactose and evaluation of its interaction with galactosyltransferase

Uridine 5'-diphospho-(2-deoxy-2-fluoro)galactose (UDP-2FGal), prepared and characterized for the first time by a chemoenzymatic method, was found to be a competitive inhibitor of beta-1,4-galactosyltransferase with a Ki value of 149 microM. This study supports that the glycosyltransferase reaction mechanism proceeds through a glycosidic cleavage transition state with sp2 character developed at the anomeric center.

Perturbing cell surface beta-(1,4)-galactosyltransferase on F9 embryonal carcinoma cells arrests cell growth and induces laminin synthesis

Cell growth and differentiation are influenced by intercellular contact, suggesting that cell adhesion molecules may be instrumental in triggering these events. F9 embryonal carcinoma cells are an ideal system in which to examine the function of cell adhesion molecules in growth and differentiation, since the relevant cell adhesion molecules and differentiation markers are well defined. Intercellular adhesion in F9 cells is mediated by uvomorulin, or E-cadherin, and cell surface beta-(1,4)-galactosyltransferase. Since previous studies suggested that neither F9 cell growth nor differentiation is directly dependent on uvomorulin function, in this study we examined whether cell surface galactosyltransferase plays any role in F9 cell growth or differentiation. A variety of galactosyltransferase perturbants, including anti-galactosyltransferase antibodies, UDPgalactose, and the substrate modifier protein alpha-lactalbumin, inhibited the growth of F9 cells, whereas control reagents did not. To examine this in more detail, we analyzed the effects of perturbing surface galactosyltransferase on progression through the F9 cell cycle. Anti-galactosyltransferase IgG treatment inhibited ornithine decarboxylase activity and lengthened the F9 cell cycle during G1 and G2, the latter mimicking the effects of retinoic acid, a reagent known to prolong the F9 cell cycle and induce differentiation. In contrast, anti-uvomorulin antibodies had no effect on F9 cell growth, ornithine decarboxylase activity, or progression through the cell cycle. Furthermore, perturbation of surface galactosyltransferase adhesions in F9 cell aggregates induced precocious F9 cell differentiation, as assayed by increased laminin synthesis, whereas control reagents had no effect. Thus, perturbing surface galactosyltransferase adhesions in F9 cells both decreases growth and stimulates synthesis of laminin. These results imply that interactions between surface galactosyltransferase and its oligosaccharide ligand during cell adhesion may affect the normal growth-regulatory and differentiation-inducing signals, as is seen, in part, during treatment with retinoic acid.