MPO uses NO$2−$ and tyrosine as substrates to promote peroxidation of endogenous plasma lipids under physiologically relevant conditions.

Isolated MPO (30 nM) and an H₂O₂-generating system (G/GO) (10 μM/h flux of H₂O₂) were incubated with dialyzed plasma (50%, vol/vol) and the indicated concentrations of NO$2−$ and 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 contents of 9-H(P)ODE and 9-H(P)ETE were then determined as described in “Materials and methods.”