Azzout B, Peret J
Diabete Metab. 1984 Sep;10(3):165-70.
The short-term regulation of pyruvate kinase in rat hepatocytes was studied during a feeding cycle or progressive fasting. In fed and fasted rats, the activity ratio of pyruvate kinase (V0.5-mMPEP/Vmax) in crude extracts was directly correlated with the concentration of glucose 1,6-bisphosphate++ in hepatocytes. Precipitation of the enzyme from homogenates with ammonium sulphate, which removes fructose 1,6-bisphosphate, induced in both groups of animals a low activity ratio of pyruvate kinase which remained unchanged during the whole experiment. These results show that in absence of added glucagon in hepatocytes, the activity of pyruvate kinase is mainly controlled by the intracellular level of fructose 1,6-bisphosphate. Addition of glucagon to hepatocytes from fed or fasted rats inactivated pyruvate kinase and decreased the concentration of fructose 1,6-bisphosphate in cells. However, in crude extracts both the activity ratio of pyruvate kinase and fructose 1,6-biphosphate levels were higher in fed rats than in starved rats. These findings suggest that glucagon-induced inactivation of pyruvate kinase also depends upon the concentration of fructose 1,6-biphosphate in hepatocytes.
在进食周期或渐进性禁食过程中，对大鼠肝细胞中丙酮酸激酶的短期调节进行了研究。在喂食和禁食的大鼠中，粗提物中丙酮酸激酶的活性比（V0.5-磷酸烯醇丙酮酸/Vmax）与肝细胞中1,6-二磷酸葡萄糖的浓度直接相关。用硫酸铵从匀浆中沉淀该酶，去除了1,6-二磷酸果糖，在两组动物中均诱导出低活性比的丙酮酸激酶，且在整个实验过程中保持不变。这些结果表明，在肝细胞中不添加胰高血糖素的情况下，丙酮酸激酶的活性主要受细胞内1,6-二磷酸果糖水平的控制。向喂食或禁食大鼠的肝细胞中添加胰高血糖素会使丙酮酸激酶失活，并降低细胞中1,6-二磷酸果糖的浓度。然而，在粗提物中，喂食大鼠的丙酮酸激酶活性比和1,6-二磷酸果糖水平均高于饥饿大鼠。这些发现表明，胰高血糖素诱导的丙酮酸激酶失活也取决于肝细胞中1,6-二磷酸果糖的浓度。
