Methyl 3-amino-3-deoxy-β-d-galactopyranosyl-(1 → 4)-2-acetamido-2-deoxy-β-d-glucopyranoside: An inhibitor of UDP-d-galactose: β-d-galactopyranosyl-(1 → 4)-2-acetamido-2-deoxy-d-glucose (1 → 3)-α-d-galactopyranosyltransferase

UDP-d-galactose: β-d-galactopyranosyl-(1 → 4)-2-acetamido-2-deoxy-d-glucose α-(1 → 3)-d-galactopyranosyltransferase [E.C. 2.4.1.151] transfers d-galactosyl-residues from the sugar nucleotide with retention of configuration. We report here that synthetic methyl 3′-amino-3′-deoxy-N-acetyllactosaminide (9), where the hydroxyl group normally undergoing galactosylation has been replaced by amino group, is an inhibitor for this enzyme with Ki = 104 μM. The mode of inhibition is not competitive, but appears to be specific, since other glycosyltransferases were not affected by 9.