Effect of ethanol on the peptic degradation of gastric mucus glycoprotein.
Effect of ethanol on the peptic degradation of gastric mucus glycoprotein.
复制标题
乙醇对胃粘液糖蛋白消化性降解的影响。
作者：
Laszewicz,W;Slomiany,A;Murty,VL;Liau,YH;Slomiany,BL
研究了乙醇对胃蛋白酶对胃黏液糖蛋白水解活性的影响。从猪胃中分离出未降解的黏液糖蛋白，与胃蛋白酶在有和无乙醇的条件下孵育，用三硝基苯基法测定其释放的α-氨基残基。在没有乙醇的情况下，蛋白水解速率与黏液糖蛋白浓度成正比，直至450 μg，并随孵育至少30分钟的时间保持不变。胃蛋白酶对猪胃粘液糖蛋白的表观km值为8.7 × 10-7M。乙醇抑制了胃蛋白酶对黏液糖蛋白的水解活性。在0.8 M以下，抑制率与乙醇浓度成正比，呈竞争型。双倒数图计算乙醇的表观k1值为2.2 × 10-6M。乙醇对胃黏液糖蛋白蛋白水解的抑制作用可能具有生理意义。
The effect of ethanol on the proteolytic activity of pepsin towards gastric mucus glycoprotein was investigated. Undegraded mucus glycoprotein isolated from pig stomach was incubated with pepsin in the presence and absence of ethanol, and the released α-amino residues were quantitated by the trinitrophenylation procedure. In the absence of ethanol the rate of proteolysis was proportional to mucus glycoprotein concentration up to 450 μg and remained constant with time of incubation for at least 30 min. The apparent Kmvalue of pepsin for pig gastric mucus glycoprotein was 8.7 × 10-7M. The proteolytic activity of pepsin towards mucus glycoprotein was inhibited by ethanol. The rate of inhibition was proportional to the ethanol concentration up to 0.8 M and was of competitive type. The apparent K1value calculated from the double-reciprocal plots for ethanol was 2.2 × 10-6M. The inhibitory effect of ethanol on the proteolysis of gastric mucus glycoprotein may be of physiological significance.