Sommercorn J, Freedland R A
J Nutr. 1984 Aug;114(8):1462-9. doi: 10.1093/jn/114.8.1462.
We determined the effects of diets that have different lipogenic potentials on hepatic concentrations of 6-phosphogluconate and fructose 2,6-bisphosphate, both of which activate hepatic phosphofructokinase. Diets high in carbohydrate increased concentrations of both effectors compared to a high protein (gluconeogenic) diet. The concentration of 6-phosphogluconate was associated with the lipogenic nature of the diet, and the range of its concentration matched that over which phosphofructokinase responds to 6-phosphogluconate in vitro. In contrast, the concentration of fructose of 2,6-bisphosphate was not associated with the lipogenic potential of the diets. Fructose 2,6-bisphosphate was either absent from liver or its concentration was 10- to 30-fold higher than the concentration that gives the maximal activation of phosphofructokinase in vitro. The results indicate that fructose 2,6-bisphosphate and 6-phosphogluconate have different roles in the regulation of phosphofructokinase. Fructose 2,6-bisphosphate may be involved in switching hepatic carbohydrate metabolism between gluconeogenesis and glycolysis, whereas changes in the concentration of 6-phosphogluconate may coordinate the disposition of glucose 6-phosphate between the oxidative branch of the hexosemonophosphate pathway and glycolysis. In the course of our studies, we improved an enzymatic assay for fructose 2,6-bisphosphate.
我们确定了具有不同生脂潜力的饮食对肝内6-磷酸葡萄糖酸和果糖2,6-二磷酸浓度的影响，这两种物质均可激活肝磷酸果糖激酶。与高蛋白（糖异生）饮食相比，高碳水化合物饮食会增加这两种效应物的浓度。6-磷酸葡萄糖酸的浓度与饮食的生脂特性相关，其浓度范围与磷酸果糖激酶在体外对6-磷酸葡萄糖酸的反应范围相匹配。相比之下，果糖2,6-二磷酸的浓度与饮食的生脂潜力无关。肝脏中要么不存在果糖2,6-二磷酸，要么其浓度比在体外使磷酸果糖激酶达到最大激活的浓度高10至30倍。结果表明，果糖2,6-二磷酸和6-磷酸葡萄糖酸在磷酸果糖激酶的调节中具有不同作用。果糖2,6-二磷酸可能参与肝脏碳水化合物代谢在糖异生和糖酵解之间的转换，而6-磷酸葡萄糖酸浓度的变化可能协调6-磷酸葡萄糖在磷酸己糖途径氧化分支和糖酵解之间的分配。在我们的研究过程中，我们改进了一种果糖2,6-二磷酸的酶促测定方法。
