Table S1. Compounds mixtures (ten-in-one) information. from Small molecule activates citrullination through targeting PAD2

Citrullination is a post-translational modification catalysed by peptidyl arginine deiminase (PAD) enzymes, dysregulation of protein citrullination is involved in various pathological disorders. During the last decade, a panel of citrullination inhibitors have been developed, while small molecules activating citrullination are rarely reported so far. In the study, we screened citrullination activator using an antibody against citrullinated histone H3 (cit-H3), and a natural compound demethoxycurcumin (DMC) significantly activated citrullination. The requirement of PAD2 for DMC-activated citrullination was confirmed by loss of functional assay. Notably, DMC directly engaged with PAD2, and showed binding selectivity among PAD family enzymes. Point mutation assay indicated that residue E352 is essential for DMC targeting PAD2. Consistently, DMC induced typical phenotypes of cells with dysregulation of PAD2 activity, including citrullination-associated cell apoptosis and DNA damage. Overall, our study not only presents a strategy for rationally screening citrullination activator, but also provides a chemical approach for activating protein citrullination.This article is part of the Theo Murphy meeting issue ‘The virtues and vices of protein citrullination’.