Studies on the inhibition of sialyl- and galactosyltransferases

The inhibition of the alpha-2,6-sialyltransferase from rat liver, the alpha-2,3-sialyltransferase from porcine submandibular gland and of the galactosyltransferase from human milk were studied using monosaccharide-, nucleoside- and nucleotide-derivatives of their naturally occurring donor substrates cytidine 5'-monophosphate-N-acetylneuraminic acid and uridine 5'-diphosphate-galactose, respectively. Only the corresponding nucleosides/nucleotides showed inhibitory activity. Periodate oxidation of CMP or CMP-Neu5Ac and of UMP or UDP-Gal led to reduced inhibitory efficiency with the respective transferase, The type and reversibility of the inhibition of some of these compounds, as well as the corresponding K-i values were determined.