MPO-initiated oxidation of LDL lipids in the presence of multiple competing cosubstrates.

(left) Isolated MPO (30 nM) and an H₂O₂-generating system (G/GO) (10 μM/h flux of H₂O₂) were incubated with LDL (0.2 mg/mL) and the indicated concentrations of either SCN⁻, 17β-estradiol, NO$2−$⁠, or tyrosine in 50 mM sodium phosphate buffer (pH 7.0), supplemented with 100 μM DTPA and 100 mM NaCl. After incubation at 37°C for 12 hours, the content of CE-H(P)ODE was then determined as described in “Materials and methods.” (right) Isolated MPO (30 nM), an H₂O₂-generating system (G/GO) (10 μM/h flux of H₂O₂), and physiological levels of Cl⁻ (100 mM), Br⁻ (100 μM), NO$2−$ (5 μM), tyrosine (100 μM), and LDL (0.2 mg/mL) were collectively incubated with the indicated concentrations of SCN⁻ and 17β-estradiol in 50 mM sodium phosphate buffer (pH 7.0), supplemented with 100 μM DTPA. After incubation at 37°C for 12 hours, the content of CE-H(P)ODE was then determined as described in “Materials and methods.”