The Role of Dehydroascorbate in Disulfide Bond Formation
The Role of Dehydroascorbate in Disulfide Bond Formation
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DOI：
10.1089/ars.2009.2674
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发表时间：
2010-01-01
影响因子：
6.6
通讯作者：
Ruddock, Lloyd W.
中科院分区：
文献类型：
--
作者：
Saaranen, Mirva J.;Karala, Anna-Riikka;Ruddock, Lloyd W.
脱氢抗坏血酸（DHA）是一种较高氧化态的抗坏血酸，通过其作为细胞内抗氧化剂的作用形成。DHA再循环回到抗坏血酸被认为是由多种酶催化的，包括蛋白质二硫键异构酶（PDI），其将抗坏血酸代谢与内质网（ER）中的氧化蛋白质折叠相联系。在这里，我们研究PDI作为脱氢抗坏血酸还原酶的可能作用。我们发现反应太慢，不能成为ER中DHA还原的主要途径，还原PDI与DHA反应的二级速率常数仅为12.5 M-1 s（-1）。其他硫氧还蛋白超家族成员也有类似的数量级。然而，谷氧还蛋白能够通过单硫醇机制更快地催化二十二碳六烯酸的还原。此外，DHA可以与许多其他二硫醇系统快速反应，包括以不依赖于PDI的方式与未折叠或部分折叠蛋白质中的二硫醇反应，二级速率常数高达186 M-1 s（-1）。此外，我们确定硼酸盐作为一种有效的抑制剂，催化和非催化的DHA还原在体外。这项研究提供了深入了解抗坏血酸代谢和氧化蛋白质折叠之间的联系，并提出了一种新的抗坏血酸代谢和硼酸盐毒性之间的联系。抗氧化剂。氧化还原信号。12，15-25。
Dehydroascorbate (DHA) is a higher oxidation state of ascorbate formed through its action as an intracellular antioxidant. The recycling of DHA back to ascorbate is thought to be catalyzed by a variety of enzymes, including protein disulfide isomerase (PDI), linking ascorbate metabolism to oxidative protein folding in the endoplasmic reticulum (ER). Here we examine the possible role of PDI as a dehydroascorbate reductase. We find the reaction too slow to be the major route for reduction of DHA in the ER, with a second-order rate constant for the reaction of reduced PDI with DHA of only 12.5 M-1 s(-1). Rates of a similar order of magnitude were obtained for other thioredoxin-superfamily members. However, glutaredoxin was able to catalyze DHA reduction more rapidly through a monothiol mechanism. In addition, DHA can rapidly react with many other dithiol systems, including dithiols in unfolded or partially folded proteins in a PDI-independent manner, with second-order rate constants of up to 186 M-1 s(-1). Furthermore, we identify borate as a potent inhibitor of catalyzed and non-catalyzed DHA reduction in vitro. This study both provides insights into the link between ascorbate metabolism and oxidative protein folding and suggests a novel link between ascorbate metabolism and borate toxicity. Antioxid. Redox Signal. 12, 15-25.