Oxidative stress is accepted as a key mechanism of silver nanoparticle (AgNP) toxicity in living organisms. Therefore, mechanistic studies related to the impact of AgNPs on the structure and function of antioxidant enzymes at the molecular level are essential for a comprehensive evaluation of their toxicity. By using a combination of spectroscopic, imaging and fractionation techniques, we explored the interactions between citrate-coated AgNPs (20 nm) and two key antioxidant enzymes: catalase (CAT) and superoxide dismutase (SOD). Both enzymes interacted with AgNPs by forming surface complexes. Only CAT was able to promote AgNP dissolution, without the impact of the released Ag ions on its heme cofactor. Instead, our results suggest that the formation of the AgNP–CAT complex induced conformation changes in the CAT, which resulted in an impairment of its enzymatic activity together with Ag(I) adsorption. By contrast, the formation of the AgNP–SOD complex has only a marginal influence on the protein conformation and has no impact on its metallic cofactors, and thus its enzymatic activity. Overall, the results showed that the changes in the protein conformation and the dissolution of AgNPs depended on the protein structure and could result in different degrees of enzymatic activity modulation.

中文翻译：

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银纳米颗粒与抗氧化酶的相互作用

氧化应激被认为是生物体内银纳米颗粒（AgNP）毒性的关键机制。因此，与AgNPs在分子水平上对抗氧化酶的结构和功能的影响有关的机理研究对于全面评估其毒性至关重要。通过结合使用光谱，成像和分级分离技术，我们探索了柠檬酸盐包被的AgNP（20 nm）与两种关键的抗氧化酶：过氧化氢酶（CAT）和超氧化物歧化酶（SOD）之间的相互作用。两种酶都通过形成表面复合物与AgNPs相互作用。只有CAT能够促进AgNP溶解，而释放的Ag离子对其血红素辅因子没有影响。相反，我们的结果表明，AgNP-CAT复合物的形成引起CAT中的构象变化，I）吸附。相比之下，AgNP–SOD复合物的形成仅对蛋白质构象产生很小的影响，而对其金属辅因子及其酶活性没有影响。总体而言，结果表明，蛋白质构象的变化和AgNPs的溶解取决于蛋白质的结构，并可能导致不同程度的酶活性调节。