Figure 2.

Inhibition of GST-PAD4 citrullination activity by compound 2 (A), 3 (B), 4 (C), and 6 (D). The residual activity of GST-PAD4 was plotted against the inhibitor compound concentration. Reaction rates were determined by pre-incubating GST-PAD4 and each compound in the presence of 10 mM CaCl₂ and 0.5 mM DTT for 30 min prior to the addition of 0.25 mM Dansyl-Gly-Arg to initiate the enzyme assay. Individual samples were analyzed by HPLC and product amount was estimated based on the peak area and compared to the GST-PAD4-released product in the same reaction buffer in the absence of the compounds. Experimental data (circles, compound 2; squares, compound 3; triangles, compound 4, and diamonds, compound 6) as well as the fitted model (curves) are shown. Results are expressed as mean ± SD, with n = 3.