Effect of ethanol on the enzymatic sulfation of glycosphingolipids in gastric mucosa.

The enzyme activity which catalyzes the transfer of sulfate group from 3'-phosphoadenosine 5'-phosphosulfate to C-3 of the galactose residue of galactosylceramide and lactosylceramide has been demonstrated in the Triton X-100 extracts of the microsomal fraction of rat gastric mucosa. The sulfotransferase activity of this fraction in antral mucosa was 1.2-1.3 times greater than that of the body and 19-22 times greater than that of the forestomach. The enzyme did not catalyze the transfer of sulfate to glucosylceramide, trihexosylceramide, and triglucosyl monoalkylmonoacylglycerol. Optimum enzymatic activity was obtained using 0.4% Triton X-100, 33 mM NaF, and 15 mM MgCl2 at a pH of 6.8. The sulfotransferase activity was inhibited by ethanol. With both glycolipid substrates, little inhibition of enzyme activity was obtained up to 0.5 M ethanol. However, higher concentrations of ethanol produced severe inhibitory effect. This inhibition of sulfation of galactosylceramide and lactosylceramide by ethanol was of the competitive type. The apparent KI values were 8.3 X 10(-5) for galactosylceramide and 5.6 X 10(-5) for lactosylceramide.