Single colonies of transformed cells were transferred into sterile 96-well plates (MTP) containing 100 μl of LB medium supplemented with ampicillin (100 μg/ml). The plates were covered with air-pore membrane and cultivated for 3 h at 37°C and 200 rpm. After that, an additional 100 μl of LB medium with ampicillin (100 μg/ml) and IPTG (1 mM) were added to the mini-cultures and MTP was afterward incubated at 20°C, 200 rpm, for 18 hours. Cell cultures were harvested by centrifugation at 4°C, 1600 x g, 20 min. The supernatant was discarded, and the cell pellets were washed with 200 μl of reaction buffer (1 mM orthovanadate, 20 mM phosphate buffer, pH = 8.0). MTP was centrifuged again at 4°C, 1600 g, 20 min and the washing step was repeated twice. Finally, the pellets were resuspended in 200 μl of the reaction buffer, and optical density (OD600) was determined spectrophotometrically. Into each well of a new black bottom 96-well MTP plate, 100 μl of MasterMix was dispensed: 25 μM aminophenyl fluorescein, 26 mM H2O2, 1.1 U Curvularia inaequalis vanadium chloroperoxidase with additional His tag, 1 mM orthovanadate, 20 mM phosphate buffer, pH = 8.0. Also, 4 μl of resuspended cells were added into each well, followed by the addition of 96 μl of 0.3 mM 1,2-dibromoethane in the reaction buffer. Fluorescence was measured using Synergy™ H4 Hybrid Microplate Reader (BioTek, USA) (Excitation at 488 nm; emission detection at 525 nm; 30°C). Data for all tested variants were measured in four biological replicates and average activity with a standard deviation of four measurements was determined.