Protein carbonylation

Protein carbonylation is an irreversible, oxidative post-translational modification in which carbonyl groups (aldehydes or ketones) are introduced into protein side chains, most often at proline, arginine, lysine, and threonine residues, either by direct metal-catalysed oxidation or by Michael addition of reactive lipid electrophiles such as 4-HNE. Carbonylated proteins are structurally altered, tend to form aggregates, and are poor proteasomal substrates, making their accumulation a marker of proteostatic stress. Carbonyl content rises progressively with biological age across species and is elevated in tissues affected by Alzheimer's disease, Parkinson's disease, and chronic obstructive pulmonary disease, establishing it as a widely used biomarker of cumulative oxidative damage.