Peptidylarginine deiminases (PADs) catalyze the calcium-dependent conversion of arginine residues to citrulline residues on target proteins. This type of posttranslational modification, called citrullination, plays an important role in the rapid disassembly of large intracellular macromolecular complexes.
Among the five members of the PAD family, PAD2 and PAD4 have been studied the most because of their abundant expression in immune cells. In macrophages, PAD2 mediates the citrullination of vimentin and breakdown of the intermediate filament network. PAD2 is also expressed in the brain where it citrullinates myelin basic protein in neurons.
Although PAD2 plays multiple roles in normal cellular homeostasis, it has also been implicated in a number of autoimmune diseases including multiple sclerosis and rheumatoid arthritis.
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