Faculty of Applied Sciences and Biotechnology, Shoolini University, Solan, India.
Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, Special Administrative Region, People's Republic of China.
Free Radic Biol Med. 2019 Dec;145:321-329. doi: 10.1016/j.freeradbiomed.2019.09.034. Epub 2019 Sep 30.
Peroxiredoxins (Prxs), scavenge cellular peroxides by forming recyclable disulfides but under high oxidative stress, hyperoxidation of their active-site Cys residue results in loss of their peroxidase activity. Saccharomyces cerevisiae deficient in human Prx (hPrx) orthologue TSA1 show growth defects under oxidative stress. They can be complemented with hPRXI but not by hPRXII, but it is not clear how the disulfide and hyperoxidation states of the hPrx vary in yeast under oxidative stress. To understand this, we used oxidative-stress sensitive tsa1tsa2Δ yeast strain to express hPRXI or hPRXII. We found that hPrxI in yeast exists as a mixture of disulfide-linked dimer and reduced monomer but becomes hyperoxidized upon elevated oxidative stress as analyzed under denaturing conditions (SDS-PAGE). In contrast, hPrxII was present predominantly as the disulfide in unstressed cells and readily converted to its hyperoxidized, peroxidase-inactive form even with mild oxidative stress. Interestingly, we found that plant extracts containing polyphenol antioxidants provided further protection against the growth defects of the tsa1tsa2Δ strain expressing hPrx and preserved the peroxidase-active forms of the Prxs. The extracts also helped to protect against hyperoxidation of hPrxs in HeLa cells. Based on these findings we can conclude that resistance to oxidative stress of yeast cells expressing individual hPrxs requires the hPrx to be maintained in a redox state that permits redox cycling and peroxidase activity. Peroxidase activity decreases as the hPrx becomes hyperoxidized and the limited protection by hPrxII compared with hPrxI can be explained by its greater sensitivity to hyperoxidation.
过氧化物酶（Prxs）通过形成可回收的二硫键来清除细胞内的过氧化物，但在高氧化应激下，其活性部位 Cys 残基的过氧化为其过氧化物酶活性的丧失。酿酒酵母缺乏人过氧化物酶（hPrx）同源物 TSA1 在氧化应激下表现出生长缺陷。它们可以被 hPRXI 互补，但不能被 hPRXII 互补，但不清楚在氧化应激下酵母中 hPrx 的二硫键和过氧状态如何变化。为了理解这一点，我们使用对氧化应激敏感的 tsa1tsa2Δ酵母菌株表达 hPRXI 或 hPRXII。我们发现酵母中的 hPrxI 以二硫键连接的二聚体和还原的单体混合物的形式存在，但在变性条件下（SDS-PAGE）分析时，随着氧化应激的增加，它会变得过氧。相比之下，hPrxII 在未受应激的细胞中主要以二硫键的形式存在，即使在轻度氧化应激下，也很容易转化为其过氧、失活的形式。有趣的是，我们发现含有多酚抗氧化剂的植物提取物为表达 hPrx 的 tsa1tsa2Δ 菌株的生长缺陷提供了进一步的保护，并保持了 Prxs 的过氧化物酶活性形式。提取物还有助于防止 hPrxs 在 HeLa 细胞中的过氧。基于这些发现，我们可以得出结论，表达单个 hPrxs 的酵母细胞对氧化应激的抗性需要 hPrx 保持在允许氧化还原循环和过氧化物酶活性的氧化还原状态。过氧化物酶活性随着 hPrx 的过氧而降低，与 hPrxI 相比，hPrxII 的保护作用有限，可以解释为其对过氧更为敏感。
