Puskás F, Braun L, Csala M, Kardon T, Marcolongo P, Benedetti A, Mandl J, Bánhegyi G
Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University of Medicine, Budapest, Hungary.
FEBS Lett. 1998 Jul 3;430(3):293-6. doi: 10.1016/s0014-5793(98)00678-4.
The orientation of gulonolactone oxidase activity was investigated in rat liver microsomes. Ascorbate formation upon gulonolactone addition resulted in higher intravesicular than extravesicular ascorbate concentrations in native microsomal vesicles. The intraluminal ascorbate accumulation could be prevented or the accumulated ascorbate could be released by permeabilising the vesicles with the pore-forming alamethicin. The formation of the other product of the enzyme, hydrogen peroxide caused the preferential oxidation of intraluminal glutathione in glutathione-loaded microsomes. In conclusion, these results suggest that the orientation of the active site of gulonolactone oxidase is intraluminal and/or the enzyme releases its products towards the lumen of the endoplasmic reticulum.
在大鼠肝脏微粒体中研究了古洛糖酸内酯氧化酶活性的方向。添加古洛糖酸内酯后形成的抗坏血酸导致天然微粒体囊泡内的抗坏血酸浓度高于囊泡外。通过用成孔剂阿拉霉素使囊泡通透，可以防止腔内抗坏血酸的积累，或者释放积累的抗坏血酸。该酶的另一种产物过氧化氢的形成导致谷胱甘肽负载的微粒体中腔内谷胱甘肽的优先氧化。总之，这些结果表明古洛糖酸内酯氧化酶活性位点的方向是腔内的，和/或该酶向内质网腔释放其产物。
