29086-04-2Relevant articles and documents
Evaluation of analogues of GalNAc as substrates for enzymes of the Mammalian GalNAc salvage pathway
Pouilly, Sabrina,Bourgeaux, Vanessa,Piller, Friedrich,Piller, Veronique
body text, p. 753 - 760 (2012/08/08)
Changes in glycosylation are correlated to disease and associated with differentiation processes. Experimental tools are needed to investigate the physiological implications of these changes either by labeling of the modified glycans or by blocking their biosynthesis. N-Acetylgalactosamine (GalNAc) is a monosaccharide widely encountered in glycolipids, proteoglycans, and glycoproteins; once taken up by cells it can be converted through a salvage pathway to UDP-GalNAc, which is further used by glycosyltransferases to build glycans. In order to find new reporter molecules able to integrate into cellular glycans, synthetic analogues of GalNAc were prepared and tested as substrates of both enzymes acting sequentially in the GalNAc salvage pathway, galactokinase 2 (GK2) and uridylpyrophosphorylase AGX1. Detailed in vitro assays identified the GalNAc analogues that can be transformed into sugar nucleotides and revealed several bottlenecks in the pathway: a modification on C6 is not tolerated by GK2; AGX1 can use all products of GK2 although with various efficiencies; and all analogues transformed into UDP-GalNAc analogues except those with alterations on C4 are substrates for the polypeptide GalNAc transferase T1. Besides, all analogues that could be incorporated in vitro into O-glycans were also integrated into cellular O-glycans as attested by their detection on the cell surface of CHO-ldlD cells. Altogether our results show that GalNAc analogues can help to better define structural requirements of the donor substrates for the enzymes involved in GalNAc metabolism, and those that are incorporated into cells will prove valuable for the development of novel diagnostic and therapeutic tools.
Haloacetamido analogues of 2-amino-2-deoxy-d-glucose and 2-amino-2-deoxy-d-galactose. Syntheses and effects on the Friend murine erythroleukemia
Fondy,Roberts,Tsiftsoglou,Sartorelli
, p. 1222 - 1225 (2007/10/07)
2-Deoxy-2(haloacetamido)-D-glucose and 2-deoxy-2-(haloacetamido)-D-galactose (fluoro, chloro, and bromo) were prepared by de-O-acetylation of the appropriate 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(haloacetamido)-β-D-hexose with triethylamine. The 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(chloroacetamido)- and 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(bromoacetamido)-β-D-hexoses were produced by condensation of a haloacetyl anhydride with 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-β-D-hexose hydrochloride in pyridine. The hydrochlorides were converted to free bases for condensation with fluoroacetic acid in the presence of dicyclohexylcarbodiimide to produce 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(fluoroacetamido)-β-D-hexoses. The chloroacetamido and bromoacetamido derivatives were from 3- to 12-fold more toxic on a molar basis to BDF1 mice when administerd as lipophilic tetra-O-acetates than as the free sugars; no significant difference existed between the glucose and galactose forms. The fluoroacetamido analogue of the glucose series was fivefold more toxic than the comparable fluoroacetamido derivative of the galactose series; no difference existed in the toxicities of the free sugars and the tetra-O-acetates with either of the fluoseries; no difference existed in the toxicities of the free sugars and the tetra-O-acetates with either of the fluoroacetamide-containing hexoses. Cytotoxicity against log-phase cultured Friend erythroleukemia cells was greatest with the tetra-O-acetylated bromoacetamido derivatives in both the gluco and galacto series, these agents being three- to fourfold more cytotoxic than tetra-O-acetylated chloroacetamido derivatives and 20-fold more cytotoxic than tetra-O-acetylated fluoroacetamido sugars. The N-chloroacetamido derivative in the glucose series was 50-fold more cytotoxic as the tetra-O-acetate than as the free nonacetylated sugar. These results support the concept that tetra-O-acetylated derivatives of the chloroacetamido and bromoacetamido carbohydrate analogues function as lipophilic alkylating agents and lose biological activity when converted to hydrophilic free hydroxyl forms, whereas the fluoroacetamido derivatives exert their effects as the de-O-acetylated form.
