Myeloperoxidase (MPO) is a heme-based peroxidase enzyme responsible for antimicrobial activity against a wide range of organisms. It has also been found to be correlated with increased oxidative stress and decreased levels of catalase activity.
The OxiSelect™ Myeloperoxidase Chlorination Activity Assay Kit is a quantitative colorimetric assay for measuring the myeloperoxidase activity within a sample. The MPO enzyme catalyzes the reaction of hydrogen peroxide (H2O2) with chloride ions to create hypochlorous acid (HOCl), which rapidly reacts with taurine to produce a stable taurine chloramine product. This step readily neutralizes the HOCl, which would otherwise accumulate and inactivate MPO. A catalase-containing stop solution is added to stop MPO catalysis by eliminating hydrogen peroxide. Finally, taurine chloramine reacts with the yellow TNB chromogen probe, with a decrease in color indicating higher MPO activity.