Bauer B A, Younathan E S
Clin Physiol Biochem. 1984;2(4):137-45.
The activities of phosphofructokinase, aldolase and pyruvate kinase were diminished in extracts from skeletal muscle of streptozotocin diabetic rats, whereas the activities of glucose phosphate isomerase and phosphoglucomutase were not changed. Treatment of diabetic rats with insulin restored the activity of phosphofructokinase to normal. A kinetic study of the partially purified enzyme from normal and diabetic rats showed identical Michaelis constants for ATP and equal sensitivity to inhibition by excess of this substrate. Extracts of quick frozen muscle from diabetic rats had higher levels of citrate (an inhibitor of phosphofructokinase) and lower levels of D-fructose-1,6-bisphosphate and D-glucose-1,6-bisphosphate (activators of this enzyme). The levels of D-fructose-6-phosphate, D-glucose-6-phosphate, ATP, ADP and AMP were the same for the two groups. Our data suggest that the in vivo decrease of phosphofructokinase activity in skeletal muscle of diabetic rats is due to a decrease in the level of the enzymatically active protein as well as to an unfavorable change in the level of several of its allosteric modulators.
链脲佐菌素诱导的糖尿病大鼠骨骼肌提取物中磷酸果糖激酶、醛缩酶和丙酮酸激酶的活性降低，而磷酸葡萄糖异构酶和磷酸葡萄糖变位酶的活性未发生变化。用胰岛素治疗糖尿病大鼠可使磷酸果糖激酶的活性恢复正常。对来自正常和糖尿病大鼠的部分纯化酶进行动力学研究表明，其对ATP的米氏常数相同，且对过量该底物抑制的敏感性相同。糖尿病大鼠速冻肌肉提取物中柠檬酸（磷酸果糖激酶的一种抑制剂）水平较高，而D-果糖-1,6-二磷酸和D-葡萄糖-1,6-二磷酸（该酶的激活剂）水平较低。两组的D-果糖-6-磷酸、D-葡萄糖-6-磷酸、ATP、ADP和AMP水平相同。我们的数据表明，糖尿病大鼠骨骼肌中磷酸果糖激酶活性的体内降低是由于酶活性蛋白水平的降低以及其几种别构调节剂水平的不利变化。
