In vitro inhibition of peptic degradation of porcine gastric mucus glycoprotein by sucralfate.

The effect of sucralfate on the proteolytic activity of pepsin towards gastric mucus glycoprotein was investigated. Mucus glycoprotein isolated from pig stomach was incubated with pepsin with and without sucralfate, and the released alpha-amino residues were quantitated. In the absence of sulcralfate the rate of proteolysis was proportional to mucus glycoprotein concentration up to 450 micrograms and remained constant with time of incubation for up to 1 h. The apparent Km value of pepsin towards mucus glycoprotein was 8.7 X 10(-7) M. Introduction of sucralfate to the reaction mixtures resulted in reduction of the rate of glycoprotein proteolysis. The rate of inhibition was proportional to the sucralfate concentration up to 1 microM and was of the competitive type, with an apparent Ki value of 2.0 X 10(-6)M. The results suggest that among the beneficial effects of sucralfate on ulcer healing, one may be attributed to its ability to interfere with peptic digestion of gastric mucus glycoprotein.