Buc H A, Demaugre F, Moncion A, Leroux J P
Biochimie. 1981 Jul;63(7):595-602. doi: 10.1016/s0300-9084(81)80057-0.
The effects of oxalate on glycolysis and glucose production from trioses were studied in hepatocytes isolated from fed and fasted rats. 1--In cells from fed rats oxalate inhibited glycolysis at the pyruvate kinase step, as shown by an increased phosphoenolpyruvate concentration, a decreased lactate and pyruvate production and a reduction of the glycolytic flux estimated by the rate of detritiation of [6-3H] glucose. The plot of 1/lactate production versus oxalate concentration showed that pyruvate kinase is a limiting step of glycolysis and allowed to determine the apparent inhibition constant for oxalate: about 3035 microM which is near the physiological concentration of blood oxalate. Under conditions where both pyruvate kinase and glycolytic flux are inhibited, oxalate had no effect on the synthesis of [14C] glucose from [14C] triose. 2--In hepatocytes prepared from fasted rats and incubated with lactate and pyruvate, oxalate decreased gluconeogenesis. In cells isolated from fasted rats and incubated with dihydroxyacetone, oxalate decreased lactate and pyruvate production whereas glucose synthesis remained unchanged. It is concluded that the inhibition of pyruvate kinase cannot by itself increase the gluconeogenic flux from triose.
研究了草酸盐对从喂食和禁食大鼠分离的肝细胞中糖酵解以及由丙糖生成葡萄糖的影响。1. 在喂食大鼠的肝细胞中，草酸盐在丙酮酸激酶步骤抑制糖酵解，这表现为磷酸烯醇丙酮酸浓度升高、乳酸和丙酮酸生成减少以及通过[6-³H]葡萄糖的氚化速率估计的糖酵解通量降低。乳酸生成的倒数与草酸盐浓度的关系图表明丙酮酸激酶是糖酵解的限速步骤，并可据此确定草酸盐的表观抑制常数：约3035微摩尔，这接近血液草酸盐的生理浓度。在丙酮酸激酶和糖酵解通量均受抑制的条件下，草酸盐对由[¹⁴C]丙糖合成[¹⁴C]葡萄糖没有影响。2. 在由禁食大鼠制备并与乳酸和丙酮酸一起孵育的肝细胞中，草酸盐降低糖异生作用。在从禁食大鼠分离并与二羟基丙酮一起孵育的细胞中，草酸盐降低乳酸和丙酮酸生成，而葡萄糖合成保持不变。得出的结论是，对丙酮酸激酶的抑制本身并不能增加来自丙糖的糖异生通量。
