Nanoplastics (NPs) are emerging global contaminants that can exacerbate the animal toxicity and cytotoxicity of cadmium (Cd). However, the mechanisms by which NPs influence the toxic effects of Cd on key functional proteins within the body remain unknown. In this study, trypsin, a protein that is prone to coexist with NPs in the digestive tract, was selected as the target protein. The effects and mechanisms of NPs on Cd2+-induced structural damage at multiple levels and alterations in the biological function of trypsin were investigated using multi-spectroscopy techniques, enzyme activity assays, and computational modeling. Results indicated that the Cd2+-induced decrease and red shift of the trypsin backbone peak were exacerbated by the presence of NPs, leading to more serve backbone loosening. Furthermore, compared to Cd2+, NPs@Cd2+ caused a more pronounced reduction in the α-helix content of trypsin. These structural changes led to the opening of the trypsin pocket and the overactivation of the enzyme (NPs@Cd2+: 227.22%; Cd2+: 53.35%). Ultimately, the formation of a “protein corona” around NPs@Cd2+ and the metal contact of Cd2+ to the trypsin surface were identified as the mechanisms by which NPs enhanced the protein toxicity of Cd2+. This study elucidates, for the first time, the effects and underlying mechanisms of NPs on the toxicity of key functional proteins of Cd2+. These findings offer novel mechanistic insights and critical evidence essential for evaluating the risks associated with NPs.

中文翻译：

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纳米塑料协同镉诱导胰蛋白酶过活的新机理见解：蛋白质多层次构象变化的联合分析和计算建模


纳米塑料 （NP） 是新兴的全球污染物，会加剧镉 （Cd） 的动物毒性和细胞毒性。然而，NPs 影响 Cd 对体内关键功能蛋白的毒性作用的机制仍然未知。在这项研究中，胰蛋白酶是一种容易与消化道中的 NPs 共存的蛋白质，被选为目标蛋白。使用多光谱技术、酶活性测定和计算建模研究了 NPs 对 Cd2 + 诱导的多层次结构损伤和胰蛋白酶生物学功能改变的影响和机制。结果表明，NPs 的存在加剧了 Cd2 + 诱导的胰蛋白酶骨架峰的降低和红移，导致更多的服务骨架松动。此外，与 Cd2+ 相比，NPs@Cd2+ 导致胰蛋白酶的 α-螺旋含量降低更明显。这些结构变化导致胰蛋白酶口袋的打开和酶的过度激活 （NPs@Cd2+： 227.22%;Cd2+：53.35%）。最终，围绕 NPs@Cd2+ 形成“蛋白电晕”和 Cd2+ 与胰蛋白酶表面的金属接触被确定为 NPs 增强 Cd2+ 蛋白质毒性的机制。本研究首次阐明了 NPs 对 Cd2+ 关键功能蛋白毒性的影响和潜在机制。这些发现为评估与 NPs 相关的风险提供了新的机制见解和关键证据。