Enzyme Inhibition Assay : Plasmepsin-2 (PM-2; Plm II) and Plasmepsin (PM-4; Plm IV) expression and purification was performed following the published protocols (Istvan E S and Goldberg D E, 2005). The final purified protein was activated by diluting the protein to 0.3 mg/mL in activating buffer (0.1 M citrate pH 4.5, 0.1% Tween-20, 50 mM dithiothreitol) and incubated at room temperature for 40 min, then the activated enzyme was diluted in assay buffer (50 mM sodium acetate pH 4.7, 0.01% Tween-20). The enzymatic inhibition reaction was performed in 384 well plates with a total volume of 20 μl. 10 μl of diluted PM-2 or PM-4 enzyme was added to the 384-well plate except blank wells (blank wells add 10 μL of assay buffer) and 20 nL of serials of diluted 1000× compounds were added to the wells with 520 Echo® Liquid Handling System (Labcyte Inc.). 10 μL PM-2 peptide substrate (AnaSpec, Cat#, 62050) with assay buffer was then added to final concentration of 20 μM to start the reaction.
Enzyme Inhibition Assay : Plasmepsin-2 (PM-2; Plm II) and Plasmepsin (PM-4; Plm IV) expression and purification was performed following the published protocols (Istvan E S and Goldberg D E, 2005). The final purified protein was activated by diluting the protein to 0.3 mg/mL in activating buffer (0.1 M citrate pH 4.5, 0.1% Tween-20, 50 mM dithiothreitol) and incubated at room temperature for 40 min, then the activated enzyme was diluted in assay buffer (50 mM sodium acetate pH 4.7, 0.01% Tween-20). The enzymatic inhibition reaction was performed in 384 well plates with a total volume of 20 μl. 10 μl of diluted PM-2 or PM-4 enzyme was added to the 384-well plate except blank wells (blank wells add 10 μL of assay buffer) and 20 nL of serials of diluted 1000× compounds were added to the wells with 520 Echo® Liquid Handling System (Labcyte Inc.). 10 μL PM-2 peptide substrate (AnaSpec, Cat#, 62050) with assay buffer was then added to final concentration of 20 μM to start the reaction.