Fiorani M, De Sanctis R, Scarlatti F, Stocchi V
Istituto di Chimica Biologica "Giorgio Fornaini", Università degli Studi di Urbino, Via Saffi 2, Urbino (PS), 61029, Italy.
Arch Biochem Biophys. 1998 Aug 15;356(2):159-66. doi: 10.1006/abbi.1998.0765.
Exposure of intact rabbit erythrocytes or erythrocyte lysates to ascorbic acid/FeCl3 in a glucose-free saline promoted a rapid decline in reduced glutathione and this response was paralleled by inactivation of hexokinase. Under the same conditions, the activity of the enzymes glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase did not show appreciablevariations in intact cells, but was severely inhibited in the cell-free system. Similar results were obtained by replacing ascorbic acid/FeCl3 with dehydroascorbic acid. In addition, both treatments effectively inhibited the activity of purified hexokinase as well as those of glucose-6-phosphate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase. Further studies using the cell-free system indicated that the inhibition of enzyme activities elicited by either of the two treatments was effectively counteracted by the specific substrates of these enzymes. The fact that the hexokinase substrate glucose freely permeates the plasma membrane, unlike the substrates of glucose-6-phosphate dehydrogenase and glyceraldehyde-3-phosphatedehydrogenase, explains the selective inhibition of hexokinase observed in intact cells. The above results also indicate that dehydroascorbic acid is an inhibitor of these enzymes and strongly suggest that it is at least in part responsible for the effects mediated by the cocktail ascorbic acid/FeCl3.
将完整的兔红细胞或红细胞裂解物暴露于无糖盐水中的抗坏血酸/氯化铁中，会导致还原型谷胱甘肽迅速减少，同时己糖激酶失活。在相同条件下，完整细胞中甘油醛-3-磷酸脱氢酶和葡萄糖-6-磷酸脱氢酶的活性没有明显变化，但在无细胞体系中受到严重抑制。用脱氢抗坏血酸替代抗坏血酸/氯化铁也得到了类似结果。此外，两种处理均有效抑制了纯化的己糖激酶以及葡萄糖-6-磷酸脱氢酶和甘油醛-3-磷酸脱氢酶的活性。使用无细胞体系的进一步研究表明，这两种处理所引发的酶活性抑制可被这些酶的特异性底物有效抵消。己糖激酶的底物葡萄糖可自由透过质膜，这与葡萄糖-6-磷酸脱氢酶和甘油醛-3-磷酸脱氢酶的底物不同，这就解释了在完整细胞中观察到的己糖激酶的选择性抑制现象。上述结果还表明脱氢抗坏血酸是这些酶的抑制剂，并强烈提示它至少部分地导致了抗坏血酸/氯化铁混合物所介导的效应。
