Andrés V, Carreras J, Cussó R
Unitat de Bioquimica, Facultat de Medicina, Universitat de Barcelona, Spain.
Int J Biochem Cell Biol. 1996 Oct;28(10):1179-84. doi: 10.1016/1357-2725(96)00046-5.
Phosphofructokinase activity is modulated by allosteric effectors and macromolecular interactions (e.g. binding to myofibrillar components). The aim of this study was to determine the effects of ATP and bisphosphorylated sugars upon phosphofructokinase in the presence of myofibrils. Myofibrils were prepared from resting and electrically stimulated rat muscle. Dephosphorylation of myofibrils was performed with alkaline phosphatase acid. Purified rabbit skeletal muscle phosphofructokinase was used for all experiments. Myofibrils from resting muscle showed a higher capacity to bind phosphofructokinase and a lower phosphate content than myofibrils from stimulated muscle. Dephosphorylation of myofibrils did not increase their binding capacity. Myofibrils greatly counteracted the inhibition of phosphofructokinase by high concentrations of ATP, without affecting maximum activity. In the presence of myofibrils, both glucose 1,6-bisphosphate and fructose 2,6-bisphosphate additionally activated muscle phosphofructokinase. We suggest that the binding of phosphofructokinase to myofibrils in combination with increasing glucose 1,6-bisphosphate concentration could be important in the enhancement of the glycolytic flux that takes place during muscle contraction.
磷酸果糖激酶的活性受变构效应物和大分子相互作用（如与肌原纤维成分结合）的调节。本研究的目的是确定在存在肌原纤维的情况下，ATP和双磷酸化糖对磷酸果糖激酶的影响。肌原纤维取自静息和电刺激的大鼠肌肉。用碱性磷酸酶对肌原纤维进行去磷酸化处理。所有实验均使用纯化的兔骨骼肌磷酸果糖激酶。与来自受刺激肌肉的肌原纤维相比，来自静息肌肉的肌原纤维具有更高的结合磷酸果糖激酶的能力和更低的磷酸盐含量。肌原纤维的去磷酸化并未增加其结合能力。肌原纤维极大地抵消了高浓度ATP对磷酸果糖激酶的抑制作用，而不影响最大活性。在存在肌原纤维的情况下，1,6-二磷酸葡萄糖和2,6-二磷酸果糖均可进一步激活肌肉磷酸果糖激酶。我们认为，磷酸果糖激酶与肌原纤维的结合，再加上1,6-二磷酸葡萄糖浓度的增加，可能对增强肌肉收缩期间发生的糖酵解通量很重要。
