组蛋白2A通过使肝微粒体通透化来刺激葡萄糖-6-磷酸酶活性。
Histone 2A stimulates glucose-6-phosphatase activity by permeabilization of liver microsomes.
作者信息
Benedetti Angelo, Fulceri Rosella, Allan Bernard B, Houston Pamela, Sukhodub Andrey L, Marcolongo Paola, Ethell Brian, Burchell Brian, Burchell Ann
机构信息
Dipartimento di Fisiopatologia e Medicina Sperimentale, University of Siena, 53100 Siena, Italy.
出版信息
Biochem J. 2002 Oct 15;367(Pt 2):505-10. doi: 10.1042/BJ20020187.
Histone 2A increases glucose-6-phosphatase activity in liver microsomes. The effect has been attributed either to the conformational change of the enzyme, or to the permeabilization of microsomal membrane that allows the free access of substrate to the intraluminal glucose-6-phosphatase catalytic site. The aim of the present study was the critical reinvestigation of the mechanism of action of histone 2A. It has been found that the dose-effect curve of histone 2A is different from that of detergents and resembles that of the pore-forming alamethicin. Inhibitory effects of EGTA on glucose-6-phosphatase activity previously reported in histone 2A-treated microsomes have been also found in alamethicin-permeabilized vesicles. The effect of EGTA cannot therefore simply be an antagonization of the effect of histone 2A. Histone 2A stimulates the activity of another latent microsomal enzyme, UDP-glucuronosyltransferase, which has an intraluminal catalytic site. Finally, histone 2A renders microsomal vesicles permeable to non-permeant compounds. Taken together, the results demonstrate that histone 2A stimulates glucose-6-phosphatase activity by permeabilizing the microsomal membrane.
组蛋白2A可增加肝微粒体中葡萄糖-6-磷酸酶的活性。这种作用要么归因于该酶的构象变化，要么归因于微粒体膜的通透性改变，从而使底物能够自由进入腔内葡萄糖-6-磷酸酶催化位点。本研究的目的是对组蛋白2A的作用机制进行批判性再研究。研究发现，组蛋白2A的剂量效应曲线不同于去污剂的剂量效应曲线，与成孔短杆菌肽的剂量效应曲线相似。在短杆菌肽通透的囊泡中也发现了之前报道的EGTA对组蛋白2A处理的微粒体中葡萄糖-6-磷酸酶活性的抑制作用。因此，EGTA的作用不能简单地被视为对组蛋白2A作用的拮抗。组蛋白2A可刺激另一种潜在的微粒体酶——UDP-葡萄糖醛酸基转移酶的活性，该酶具有腔内催化位点。最后，组蛋白2A使微粒体囊泡对非渗透性化合物具有通透性。综上所述，结果表明组蛋白2A通过使微粒体膜通透来刺激葡萄糖-6-磷酸酶的活性。
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