Quantification and significance of protein oxidation in biological samples

Protein oxidation is defined here as the covalent modification of a protein induced either directly by reactive oxygen species or indirectly by reacti on with secondary by-products of oxidative stress. Oxidative modification o f proteins can be induced experimentally by a wide array of prooxidant agen ts and occurs in vivo during aging and in certain disease conditions. Oxida tive changes to proteins can lead to diverse functional consequences, such as inhibition of enzymatic and binding activities, increased susceptibility to aggregation and proteolysis, increased or decreased uptake by cells, an d altered immunogenicity. There are numerous types of protein oxidative mod ification and these can be measured with a variety of methods. Protein oxid ation serves as a useful marker for assessing oxidative stress in vivo. The re are both advantages and disadvantages to using proteins for this purpose compared to lipids and DNA. Finally, it is important to monitor the degree of oxidative modification of therapeutic proteins manufactured for commerc ial use. This review will examine various aspects of protein oxidation, wit h emphasis on using proteins as markers of oxidative stress in biological s amples.