To obtain the parameters K _m and k _cat for Compound I, two independent methods are used. Initially, the oxidation of ADHP using the injector functionality built-in to the fluorescence plate reader is studied. The auto-injector dispenses the H ₂ O ₂ to initiate the reaction, as a means of generating a set of progress curves. Analysis for MPO-mediated oxidation of ADHP gives a K _m of 31±4 μM and the k _cat of 186± 6 s ^?1 .The k _obs also increases over the experimental range of ADHP concentrations from 1 to 80 μM and for the converse experiment holding substrate constant over 3 to 45 nM MPO. The apparent second order rate constant obtain from the slope of k _obs against ADHP concentration K ^app _on is 2.1±0.2 mM/s.