Citrullinated protein

**Citrullinated protein** refers not to a single molecular entity or classic therapeutic target, but to any protein that has undergone *citrullination* (or deimination), a post-translational modification where arginine residues are enzymatically converted to citrulline by the peptidylarginine deiminase (PAD) family of enzymes in the presence of calcium. This modification alters the protein's charge, structure, and function, and is involved in numerous physiological and pathological processes. Citrullinated proteins are key in the pathogenesis of several autoimmune disorders—most notably, anti-citrullinated protein antibodies (ACPAs) are highly specific for rheumatoid arthritis and are used as a diagnostic and prognostic biomarker. Citrullinated histones are crucial in the formation of neutrophil extracellular traps (NETs), linking citrullinated proteins to both protective immunity and inflammatory tissue damage. Aberrant citrullination also plays roles in cancer, neurodegeneration, and atherosclerosis. Small-molecule PAD inhibitors are under development to therapeutically modulate citrullination in disease contexts[1][2][3][4][5][6][7][8][10].\n\n**Note:**\n- The entry *\“Citrullinated proteins\”* is not a single, discrete molecular target; it refers to a post-translationally modified form of many different proteins. Drugs target the PAD enzymes (such as PAD4), not the citrullinated proteins per se; therefore, this is not considered a canonical therapeutic target or receptor, making this entry *incorrect* as a formal drug target[1][5][7][10].\n- For structured data, actual targets are the PAD enzymes (e.g., \“Peptidylarginine deiminase 4\”), not citrullinated proteins as a group.

Other names

Citrullinated proteinsCitrullinated self-proteinsDeiminated proteins

Inhibition of peptidylarginine deiminase (PAD) enzyme activity[5]