Recognition of synthetic analogues of the acceptor, β-D-Galp-OR, by the blood-group H gene-specified glycosyltransferase

Article abstract of DOI:10.1016/0008-6215(94)84212-4

The acceptor-substrate specificity of a cloned α-(1 → 2) fucosyltransferase has been explored using structural analogues of octyl β- D-galactopyranoside (4). This monosaccharide is the minimum acceptor- substrate for the H-transferase, one of two enzymes responsible for the biosynthesis of the O blood-group antigen, which terminates in the sequence α-L-Fucp-(1 → 2)-β-D-Galp. Galactoside 4 has a K(m) of 6 mM with this enzyme. Eighteen analogues of 4 have been prepared, including those where the hydroxyl groups at C-3, C-4, and C-6 have been replaced, independently, with deoxy, fluoro, O-methyl, amino, and acetamido functionalities. The C-3 and C- 4 epimers have been prepared as has the C-5 de(hydroxymethyl)ated derivative. These compounds were screened as potential acceptors and inhibitors of the fucosyltransferase. The C-6 analogues that do not possess a charge show substrate activity with relative rates in the range of 27-316% that of 4. The C-3 modified analogues are inhibitors with estimated K(i) values of 0.9-43 mM. Those analogues with modifications at C-4 were both poor inhibitors and acceptors. The acceptor-substrate specificity of a cloned α-(1 → 2) fucosyltransferase has been explored using structural analogues of octyl β-D-galactopyranoside (4). This monosaccharide is the minimum acceptor-substrate for the H-transferase, one of two enzymes responsible for the biosynthesis of the O blood-group antigen, which terminates in the sequence α-L-Fucp-(1 → 2)-β-D-Galp. Galactoside 4 has a K_m of 6 mM with this enzyme. Eighteen analogues of 4 have been prepared, including those where the hydroxyl groups at C-3, C-4, and C-6 have been replaced, independently, with deoxy, fluoro, O-methyl, amino, and acetamido functionalities. The C-3 and C-4 epimers have been prepared as has the C-5 de(hydroxymethyl)ated derivative. These compounds were screened as potential acceptors and inhibitors of the fucosyltransferase. The C-6 analogues that do not possess a charge show substrate activity with relative rates in the range of 27-316% that of 4. The C-3 modified analogues are inhibitors with estimated K_i values of 0.9-43 mM. Those analogues with modifications at C-4 were both poor inhibitors and acceptors.