Department of Experimental Metabolism, Center for Biomedical Research of Michoacán, Morelia, Michoacán, México.
PLoS One. 2010 Jan 29;5(1):e8971. doi: 10.1371/journal.pone.0008971.
Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems. However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin. It is leading to new concepts that even consider albumin not only as an antioxidant but as the major antioxidant in plasma known to be exposed to continuous oxidative stress. Evidence presented here establishes a previously unrecognized relationship between proteins' antioxidant capacity and structural stress.
METHODOLOGY/PRINCIPAL FINDINGS: A chemiluminiscence based antioxidant assay was achieved to quantify the antioxidant capacity of albumin and other proteins. The capabilities of proteins as antioxidants were presented, but in addition a new and powerful component of the protein antioxidant capacity was discovered. The intrinsic component, designated as Response Surplus (RS), represents a silent reserve of antioxidant power that awakens when proteins face a structural perturbation (stressor) such as temperature, short wave UV light, the same reactive oxygen species, and more extreme changes like glucose or aldehyde-mediated structural modifications. The work also highlights the importance of structural changes in protein antioxidant properties and the participation of sulfhydryl groups (SHs) in the RS antioxidant component. Based on recent evidence about the SH group chemistry, a possible model for explaining RS is proposed.
CONCLUSIONS/SIGNIFICANCE: The data presented show the significant antioxidant behavior of proteins and demonstrate the existence of a previously unrecognized antioxidant response to the stress. Several implications, including changes in elementary concepts about antioxidants and protein function, should emerge from here.
由于蛋白质在生物系统中的丰富性，它们长期以来一直被认为是氧化剂的主要靶标。然而，越来越多的证据表明，白蛋白等蛋白质具有显著的抗氧化活性。这导致了新的概念，甚至认为白蛋白不仅是一种抗氧化剂，而且是已知暴露于持续氧化应激的血浆中的主要抗氧化剂。这里提出的证据确立了蛋白质抗氧化能力与结构应激之间以前未被认识的关系。
方法/主要发现：实现了基于化学发光的抗氧化剂测定法来量化白蛋白和其他蛋白质的抗氧化能力。提出了蛋白质作为抗氧化剂的能力，但此外还发现了蛋白质抗氧化能力的一个新的强大组成部分。内在成分，指定为响应剩余（RS），代表抗氧化能力的沉默储备，当蛋白质面临结构扰动（应激源）时，如温度、短波紫外线、相同的活性氧，以及更极端的变化，如葡萄糖或醛介导的结构修饰，就会唤醒 RS。该工作还强调了蛋白质抗氧化特性中的结构变化以及巯基（SH）在 RS 抗氧化成分中的参与的重要性。基于最近关于 SH 组化学的证据，提出了一个可能的模型来解释 RS。
结论/意义：所呈现的数据显示了蛋白质的显著抗氧化行为，并证明了存在以前未被认识到的应激抗氧化反应。应该会出现几个影响，包括关于抗氧化剂和蛋白质功能的基本概念的变化。
