Romanelli A, St-Denis J F, Vidal H, Tchu S, van de Werve G
Laboratoire d'Endocrinologie Métabolique, Department of Biochemistry, Université de Montréal, Québec, Canada.
Biochem Biophys Res Commun. 1994 May 16;200(3):1491-7. doi: 10.1006/bbrc.1994.1619.
The permeability of rat liver microsomes to glucose was investigated in relation to the hexose-6-phosphate dehydrogenase system (EC 1.1.1.47). It was found that glucose-6-phosphate dehydrogenase activity could be assayed with NADP as coenzyme in both untreated and detergent-treated microsomes. However, when glucose was used as substrate, activity was only measurable in detergent-treated microsomes. Moreover, radioactive glucose added to microsomes in a variety of experimental conditions was never taken up by the vesicles. Our results indicate that NADP (or NAD) availability is probably not the reason for the absence of glucose dehydrogenase activity in untreated microsomes but rather membrane impermeability to glucose would account for the complete latency observed. This finding calls for a reevaluation of glucose transport in relation to other enzymes of the endoplasmic reticulum, such as glucose-6-phosphatase.
研究了大鼠肝微粒体对葡萄糖的通透性与己糖-6-磷酸脱氢酶系统（EC 1.1.1.47）的关系。发现在未处理的和经去污剂处理的微粒体中，均可使用NADP作为辅酶来测定葡萄糖-6-磷酸脱氢酶活性。然而，当使用葡萄糖作为底物时，活性仅在经去污剂处理的微粒体中可测。此外，在各种实验条件下添加到微粒体中的放射性葡萄糖从未被囊泡摄取。我们的结果表明，NADP（或NAD）的可用性可能不是未处理微粒体中缺乏葡萄糖脱氢酶活性的原因，而是膜对葡萄糖的不透性导致了所观察到的完全潜伏性。这一发现要求重新评估与内质网的其他酶（如葡萄糖-6-磷酸酶）相关的葡萄糖转运。
