In Vitro Assay: FVIIa-Xase Ki (37° C.): S2765 (0.5 mM), PCPS (25 μM), calcium chloride (5 mM), full-length human TF (3 nM), human FVIIa (5 pM), and FVIIa inhibitor were incubated for 15 min at 37° C. Reactions were initiated by the addition of human FX (range of concentrations). Preliminary experiments revealed that the plasma purified FX contains a residual amount of human FVIIa which could not be removed by affinity chromatography. The residual FVIIa is sufficient, when combined with PCPS, calcium and TF to catalyze the conversion of FX to Xa, and was increased by the addition of 5 pM human FVIIa. FXa in turn hydrolyses S2765, which was monitored for 60 min at 405 nm.
In Vitro Assay: Tissue kallikrein-1 (37° C) activity was determined in reactions containing 0.05 nM enzyme and 90 μM substrate (H-D-Val-Leu-Arg-AFC) in buffer (0.1M sodium phosphate pH 7.4, 0.2 M NaCl, 0.5% PEG 8000, and 1% DMSO). Assays were performed using 96-well microtiter plates (COSTAR 3600, CORNING, NY, USA) and a thermostatic temperature controlled plate reader (SPECTRAMAX® Gemini, Molecular Devices, Sunnyvale, Calif., USA). Fluorescence was monitored using 400 nm excitation and 505 nm emission wavelengths.