St-Denis J F, Annabi B, Khoury H, van de Werve G
Department of Nutrition, Université de Montréal, Québec, Canada.
Biochem J. 1995 Aug 15;310 ( Pt 1)(Pt 1):221-4. doi: 10.1042/bj3100221.
The effect of histone II-A on glucose-6-phosphatase and mannose-6-phosphatase activities was investigated in relation to microsomal membrane permeability. It was found that glucose-6-phosphatase activity in histone II-A-pretreated liver microsomes was stimulated to the same extent as in detergent-permeabilized microsomes, and that the substrate specificity of the enzyme for glucose 6-phosphate was lost in histone II-A-pretreated microsomes, as [U-14C]glucose-6-phosphate hydrolysis was inhibited by mannose 6-phosphate and [U-14C]mannose 6-phosphate hydrolysis was increased. The accumulation of [U-14C]glucose from [U-14C]glucose 6-phosphate into untreated microsomes was completely abolished in detergent-treated vesicles, but was increased in histone II-A-treated microsomes, accounting for the increased glucose-6-phosphatase activity, and demonstrating that the microsomal membrane was still intact. The stimulation of glucose-6-phosphatase and mannose-6-phosphatase activities by histone II-A was found to be reversed by EGTA. It is concluded that the effects of histone II-A on glucose-6-phosphatase and mannose-6-phosphatase are not caused by the permeabilization of the microsomal membrane. The measurement of mannose-6-phosphatase latency to evaluate the intactness of the vesicles is therefore inappropriate.
研究了组蛋白II - A对葡萄糖-6-磷酸酶和甘露糖-6-磷酸酶活性的影响，并探讨了其与微粒体膜通透性的关系。结果发现，经组蛋白II - A预处理的肝微粒体中葡萄糖-6-磷酸酶的活性与经去污剂通透处理的微粒体中受到的刺激程度相同，并且在经组蛋白II - A预处理的微粒体中，该酶对葡萄糖6-磷酸的底物特异性丧失，因为6-磷酸甘露糖抑制了[U-14C]葡萄糖-6-磷酸的水解，而[U-14C]甘露糖6-磷酸的水解增加。在去污剂处理的囊泡中，[U-14C]葡萄糖从[U-14C]葡萄糖6-磷酸积累到未处理的微粒体中的过程完全被消除，但在经组蛋白II - A处理的微粒体中有所增加，这解释了葡萄糖-6-磷酸酶活性的增加，并表明微粒体膜仍然完整。发现EGTA可逆转组蛋白II - A对葡萄糖-6-磷酸酶和甘露糖-6-磷酸酶活性的刺激作用。得出的结论是，组蛋白II - A对葡萄糖-6-磷酸酶和甘露糖-6-磷酸酶的作用不是由微粒体膜的通透化引起的。因此，通过测量甘露糖-6-磷酸酶的潜伏性来评估囊泡的完整性是不合适的。
