Oxidative stress is a term you'll see a lot when reading the literature of aging research. The more reactive oxidant compounds there are in a cell, the more they will react with important proteins, modifying them and thus causing cellular machinery to run awry or require repair. Aging is characterized by rising levels of oxidative stress, caused by things such as increased presence of metabolic byproducts that are ever more inefficiently removed, accumulating damage to mitochondria, and so forth.
This is still something of a high level picture, however, and there is still a lot of room left for researchers to expand the understanding of how exactly oxidative damage progresses, or how it contributes to specific manifestations of aging, such as increased cellular senescence. Hence we see work of this nature:
Protein damage mediated by oxidation, protein adducts formation with advanced glycated end products and with products of lipid peroxidation, has been implicated during aging and age-related diseases, such as neurodegenerative diseases.
Increased protein modification has also been described upon replicative senescence of human fibroblasts, a valid model for studying aging in vitro. However, the mechanisms by which these modified proteins could impact on the development of the senescent phenotype and the pathogenesis of age-related diseases remain elusive.
In this study, we performed in silico approaches to evidence molecular actors and cellular pathways affected by these damaged proteins. A database of proteins modified by carbonylation, glycation, and lipid peroxidation products during aging and age-related diseases was built and compared to those proteins identified during cellular replicative senescence in vitro.
Common cellular pathways evidenced by enzymes involved in intermediate metabolism were found to be targeted by these modifications, although different tissues have been examined. ... An important outcome of the present study is that several enzymes that catalyze intermediate metabolism, such as glycolysis, gluconeogenesis, the citrate cycle, and fatty acid metabolism have been found to be modified. These results indicate a potential effect of protein modification on the impairment of cellular energy metabolism. Future studies should address this important issue by combining metabolomics and targeted proteomic analysis during cellular and organismal aging.