CHEMBL5738504

Phosphodiesterase Enzyme Assay: TABLE 5: All 3′, 5′ cyclic nucleotide PDE enzyme activities are measured with a radiometric enzyme assay based on SPA detection system. Compounds to be tested are diluted in pure DMSO using ten point concentration response curves. Maximal compound concentration in the reaction mixture is either 10 or 100 μM. Compounds at the appropriate concentration are pre-incubated with either of the PDE enzymes for 30 minutes before the reaction is started by the addition of substrate. Reactions are allowed to proceed for 60 minutes at room temperature. Next, reactions are stopped by addition of SPA beads. Samples are read 12 hours later in a MICROBETA™ TRILUX© Counter. IC50 values are calculated by plotting the normalized data vs. log [compound] and fitting the data using a four parameter logistic equation.PDE1B, PDE1A, and PDE1C are cloned and purified following standard protein generation procedures. The assay buffer is prepared to give a final concentration in the assay of 50 mM Tris-HCl, 50 mM MgCl2, 4 mM CaCl2), 0.1% BSA and 6 U/mL Calmodulin in water, at pH 7.5. The final enzyme concentration is 0.25, 0.074 and 0.0012 nM, for PDE1A, PDE1B and PDE1C respectively. The reactions are started by addition of the substrate, [3H]cAMP, to give a final concentration of 47 nM.