热损伤大鼠小肠上皮细胞磷酸果糖激酶的变构特性

Allosteric properties of phosphofructokinase from the epithelial cells of thermally injured rat small intestine.

Khoja S M, Salleh M, Ardawi M

Comp Biochem Physiol B. 1987;87(3):469-72. doi: 10.1016/0305-0491(87)90038-1.

Abstract

The allosteric properties of phosphofructokinase from the epithelial cells of thermally injured rat small intestine were studied and compared with those properties of the normal rats. 2. The fructose 6-phosphate saturation curve of mucosal phosphofructokinase from thermally injured rats (3 days post injury, 33% of body surface area) displayed cooperatively; the ratio of the activity observed at pH 7.0 in the presence of 0.5 mM fructose 6-phosphate and 2.5 mM-ATP to the optimal activity at pH 8.0, v 0.5/V, was 0.42 +/- 0.02 in the normal rats and 0.22 +/- 0.03 in the injured rats. 3. The enzyme from thermally injured rats was very sensitive to inhibition by ATP as compared to that from normal rats. 4. The enzyme from thermally injured rats was inhibited by citrate and phosphocreatine in a synergistic manner with ATP. 5. Activation under nearly cellular conditions was produced by ADP, AMP and glucose-1,6-biphosphate. 6. In general, the mucosal enzyme of thermally injured rats was more susceptible to inhibition or activation by various metabolites than the enzyme of the normal rats. 7. These results may suggest that mucosal phosphofructokinase of thermally injured rats may not be subject to the same control mechanism as the normal rats in vivo due to changes in the concentrations of fructose-2,6-biphosphate.

摘要

研究了热损伤大鼠小肠上皮细胞中磷酸果糖激酶的变构特性，并与正常大鼠的该特性进行了比较。2. 热损伤大鼠（损伤后3天，体表面积的33%）黏膜磷酸果糖激酶的6-磷酸果糖饱和曲线呈协同性；在正常大鼠中，在pH 7.0、存在0.5 mM 6-磷酸果糖和2.5 mM ATP时观察到的活性与pH 8.0时的最佳活性之比，即v 0.5/V，为0.42±0.02，而在损伤大鼠中为0.22±0.03。3. 与正常大鼠的酶相比，热损伤大鼠的酶对ATP抑制非常敏感。4. 热损伤大鼠的酶被柠檬酸和磷酸肌酸与ATP协同抑制。5. 在接近细胞的条件下，ADP、AMP和1,6-二磷酸葡萄糖可产生激活作用。6. 一般来说，热损伤大鼠的黏膜酶比正常大鼠的酶更容易受到各种代谢物的抑制或激活。7. 这些结果可能表明，由于2,6-二磷酸果糖浓度的变化，热损伤大鼠的黏膜磷酸果糖激酶在体内可能不受与正常大鼠相同的控制机制的调节。