FIGURE 7.

Thiocyanate and urate compete as substrates for LPO. LPO (50 nm) was incubated with urate (400 μm) and various concentrations of thiocyanate (0–200 μm) in 50 mm phosphate buffer, pH 7.4. Reactions were started by the addition of hydrogen peroxide (20 μm) and stopped by the addition of 20 μg/ml catalase. Allantoin formation was measured by LC/MS. The concentration of thiocyanate, when allantoin formation is inhibited by 50% (IC₅₀), was determined by fitting the data as described under “Experimental Procedures” (solid line). Data are means and ranges of duplicate experiments.