| Assay Method Information | |
| | In Vitro Plasma Kallikrein Inhibition Assay |
| Description: | The chromogenic substrate D-Pro-Phe-Arg-pNa, 2HCl (BIOPHEN CS-31(02) from Hyphen BioMed, Neuville-Sur-oise, France) was dissolved in 5 mL deionized water and stored at 4° C. Concentration was determined in the spectrophotometer at 342 nm using an extinction coefficient of 8270. All other chemicals were of analytical grade.Human plasma kallikrein was purchased from Enzyme Research Labs (South Bend, Ind., USA, batch HPKa 2830). A stock solution of 7 μM in 50% glycerol was stored at −20° C.Enzyme reactions were conducted in assay buffer comprised of 20 mM HEPES at pH 7.4, 150 mM NaCl, 0.1% PEG-8000 and 0.01% Triton X-100.Both enzyme and substrate were diluted in assay buffer.The compound solutions as well as the enzyme and the substrate solutions were transferred to 96-well plates (Clear, UV-Star, Flat-bottom, Half-Area plates; cat. No. 675801 Greiner Bio-one, purchased from VWR International, Arlington Heights, Ill., USA) using a Rainin LTS 96-channel pipettor (Rainin, Columbus, Ohio, USA). Plate measurements were conducted using a SPECTROStar Nano reader (BMG Labtech, San Francisco, Calif., USA). The SPECTROStar Nano is a spectrophotometer and absorbance was measured at 405 nm. We used discrete wavelength, precise, kinetic reads of 15 cycles with a 60 sec cycle time.Determination of IC50 valuesFor the determination of IC50 values, the assays were performed at room temperature in 96-well plates with a total assay volume of 85 μL per well. The test compound was dissolved in 100% DMSO. The compounds were serially diluted in DMSO in a 7 point dose response. For the assays, 66.5 μL of protease solution (protease in assay buffer) was added per well followed by the addition of 8.5 μL of compound in 100% DMSO. The final assay concentration of the human plasma kallikrein was 250 μM. After 30 min. incubation at room temperature on an orbital shaker, the reactions were started by the addition of 10 μL substrate solution (in assay buffer, final assay concentration was 600 uM). After the addition of the substrate solution the final DMSO concentration was 10%. The plate was placed again on the shaker for 5 sec, spun at 2000 rpm for 5 sec and read on the spectrophotometer. The effect of the compound on the enzymatic activity was obtained from the linear part of the progress curves and determined after 15 minutes. |
| Affinity data for this assay | |
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