TcGPXII, a glutathione-dependent Trypanosoma cruzi peroxidase with substrate specificity restricted to fatty acid and phospholipid hydroperoxides, is localized to the endoplasmic reticulum
TcGPXII, a glutathione-dependent Trypanosoma cruzi peroxidase with substrate specificity restricted to fatty acid and phospholipid hydroperoxides, is localized to the endoplasmic reticulum
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DOI：
10.1042/bj20020038
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发表时间：
2002-06-15
影响因子：
4.1
通讯作者：
Kelly, JM
中科院分区：
文献类型：
--
作者：
Wilkinson, SR;Taylor, MC;Kelly, JM
直到最近。人们认为锥虫缺乏谷胱甘肽过氧化物酶活性。在这里，我们报告的亚细胞定位和生化特性的第二谷胱甘肽依赖性过氧化物酶从克氏锥虫（TcGPXII）。TcGPXII是编码16 kDa蛋白的单拷贝基因，该蛋白似乎特异性地依赖于谷胱甘肽作为还原当量的来源。重组TcGPXII经纯化并显示对窄底物范围具有过氧化物酶活性，仅限于脂肪酸和磷脂的氢过氧化物。对该途径的分析表明，TcGPXII活性很容易被谷胱甘肽饱和，并且过氧化物酶通过乒乓机制发挥作用。酶还原被证明是该途径中的限速步骤。使用免疫荧光，TcGPXII被证明与免疫球蛋白重链结合蛋白（BiP），限制于内质网和高尔基体的蛋白质的同源物共定位。由于滑面内质网是磷脂和脂肪酸合成的场所，这表明TcGPXII可能在T. cruzi氧化防御系统通过保护新合成的脂质免受过氧化作用。
Until recently. it had been thought that trypanosomes lack glutathione peroxidase activity. Here we report the subcellular localization and biochemical properties of a second glutathione-dependent peroxidase from Trypanosoma cruzi (TcGPXII). TcGPXII is a single-copy gene which encodes a 16 kDa protein that appears to be specifically dependent on glutathione as the source of reducing equivalents, Recombinant TcGPXII was purified and shown to have peroxidase activity towards a narrow substrate range, restricted to hydroperoxides of fatty acids and phospholipids. Analysis of the pathway revealed that TcGPXII activity could be readily saturated by glutathione and that the peroxidase functioned by a Ping Pong mechanism. Enzyme reduction was shown to be the rate-limiting step in this pathway. Using immunofluorescence, TcGPXII was shown to co-localize with a homologue of immunoglobulin heavy-chain binding protein (BiP), a protein restricted to the endoplasmic reticulum and Golgi. As the smooth endoplasmic reticulum is the site of phospholipid and fatty acid biosynthesis, this suggests that TcGPXII may play a specific role in the T. cruzi oxidative defence system by protecting newly synthesized lipids from peroxidation.