Figure 6. TK04 is a nanomolar competitive inhibitor of LTC4S.

A. Chemical structure of TK04, the inhibitor used in this study. Dose-response curves for inhibition of mouse and human LTC4S by TK04. 100% activity corresponds to the enzyme activity without inhibitor, which was 44.0 µmol min⁻¹ mg⁻¹ for the mouse enzyme (red line) and 69.7 µmol min⁻¹ mg⁻¹ for the human enzyme (black line). The concentrations of substrates GSH and LTA₄ used in the assay were 5 mM and 20 µM, respectively. The IC₅₀ for mLTC4S was 135±30 nM and for the hLTC4S it was 134±16 nM.