Prostaglandin effect on the enzymatic sulfation of mucus glycoprotein in gastric mucosa

Abstract

The effect of 16,16-dimethyl prostaglandin E 2 (DMPGE 2 on the sulfation of mucus glycoprotein in gastric mucosa was investigated. The enzymatic activity which catalyzes the transfer of the sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to gastric mucus glycoprotein was located in the detergent extracts of Golgi-rich membrane fraction of antral and body mucosa of rat stomach. The sulfotransferase activity of this fraction from body mucosa, however, was 35% higher than that from the antrum. The enzyme exhibited optimum activity at pH 6.8 using 0.5% Triton X-100 and 30 mM NaF. The apparent K m of the enzyme for sulfation of mucus glycoprotein was 10.5 μM, and the sulfate ester was found incorporated into the carbohydrate chains of the glycoprotein. Introduction of DMPGE 2 to the reaction mixtures led to an enhancement in the rate of mucus glycoprotein sulfation. The rate of enhancement was proportional to the concentration of DMPGE 2 up to 1.0 × 10 −4 M and was of the competitive type, with an apparent K m value of 6.7 μM. Since sulfated mucins play an important role in gastric mucosal defense and the increase in their sulfation occurred at levels of prostaglandin present in gastric mucosa, the observed effect may be of significance to gastric mucosal defense in vivo.