| Assay Method Information | |
| | MPO Chlorination Assay (APF Assay) |
| Description: | MPO chlorination activity was measured in 100 mM KPi (pH 7.4) by utilizing the non-fluorescent reagent Aminophenyl fluorescein (APF, Invitrogen catalog #A36003). APF is cleaved by ( OCl) to yield the fluorescent compound fluorescein. Reactions were carried out in 50 μL total volume by adding a 25 μL mixture of 200 pM myeloperoxidase and 120 mM NaCl to 100 nL inhibitor in 100% DMSO in a 384 well, non-binding surface clear bottom plate (CORNING #3655). Enzyme, inhibitor, and chloride were preincubated for ten minutes at room temperature.After the ten minute preincubation, 25 μL of an APF mixture containing 10 mM APF, 120 mM NaCl and 10 μM H2O2 was added to the plate using the internal dispensing system of a Hammatsu FDSS 6000. Kinetic determinations were carried out immediately on the FDSS 6000 (3 minute kinetic read, 1 read every second, ex: 485 nm, em: 535 nm). IC50 values for inhibitors were calculated by taking the slope of the linear portion of the kinetic measurement (20 seconds to 80-120 secs).IC50 values were calculated by determining the slope of the linear portion of the kinetic trace (180-540 secs), and using that calculated slope to determine % inhibition occurring at each concentration of inhibitor using the following equation:Y = A + B - A 1 + ( C / x ) D where A=minimal Y value (activity level of inhibited sample), B=maximal Y value (activity level of uninhibited sample), C=Log IC50, D=Hill Slope, x=concentration of inhibitor. |
| Affinity data for this assay | |
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