Myeloperoxidase (MPO) is a unique peroxidase that, in addition to its peroxidation activity, also catalyzes the conversion of hydrogen peroxide (H₂O₂) and chloride (Cl^-) to hypochlorous acid (HOCl). The EnzChek™ Myeloperoxidase (MPO) Activity Assay Kit provides assays for the determination of both chlorination and peroxidation activities of MPO in solution and in cell lysates. For detection of chlorination, the kit includes nonfluorescent 3'-(p-aminophenyl) fluorescein (APF), which is selectively cleaved by hypochlorite (^-OCl) to yield fluorescein. Peroxidation is detected using nonfluorescent Amplex™ UltraRed reagent (A36006), which is oxidized by the H₂O₂-generated redox intermediates MPO-I and MPO-II to form a fluorescent product. The EnzChek™ Myeloperoxidase Activity Assay Kit can be used to continuously detect these activities at room temperature over a broad dynamic range (1.5 to 200 ng/mL). The speed (30 minutes), sensitivity, and mix-and-read convenience make this kit ideal for measuring MPO activities and for high-throughput screening for MPO-specific inhibitors.