Fig. 7.

The mechanism of KYC inhibition of MPO. A: Effects of KYC on MPO UV-Vis spectra. a: MPO (1.4 μM) was incubated with KYC (50 μM) at room temperature. The changes in UV-Vis spectra were recorded at different times as indicated. b: The same reaction as in (a), except H₂O₂ (40 μM) was added. c: The same reaction as in (a), except 150 mM NaCl was added. d: The same reaction as in (b), except 150 mM NaCl was added. e: MPO (1.4 μM) was mixed with H₂O₂ (300 μM) for 20 sec. The reaction was stopped by addition of catalase. Immediately after recording the compound II spectrum, the reaction was mixed with KYC (50 μM) and the changes of heme spectra were recorded. B: H₂O₂ consumption of MPO. MPO (2 nM) was incubated with H₂O₂ (50 μM) and NaCl (100 mM) with different amounts of KYC in phosphate buffer (100 mM, pH 7.4) containing DTPA (100 μM) at room temperature. H₂O₂ consumption rates were determined using the Fox assay in triplicate. C: Docking of KYC in the active site of MPO (eHit v9.1, SimBioSys^TM Inc., Toronto, Canada). a: shown KYC on the top of heme of MPO active center and b: shown Tyr of KYC is almost parallel to heme of MPO active center. The blue molecule is the heme of MPO, the red molecule is KYC, and the green line is the side chain of Glu116.