| Assay Method Information | |
| | cAMP HTRF Assay to Determine the Activity of hPDE4B1 |
| Description: | The inhibiting effect of the compounds on the enzyme activity of human PDE4B1 was measured by the quantification of 5′-adenosine monophosphate (5′-AMP), which is formed from 3′,5′-cyclic adenosine monophosphate (cAMP). Human recombinant enzyme, expressed in Sf9 cells, and the HTRF (homogeneous time-resolved fluorescence) detection method were used in the assay.The test compound or water (control) was mixed with the human recombinant PDE4B1 enzyme (4.8 U) in a buffer consisting of 44.4 mM tris-HCl, 5.28 mM MgCl2, 2.64 mM DTT and 0.044% Tween 20 (pH 7.8). After adding the cAMP enzyme substrate (final concentration 40 nM), the mixture was incubated for 30 minutes at room temperature. Then a fluorescence acceptor (Dye2 marked with cAMP), a fluorescence donor (anti-cAMP antibody marked with a europium cryptate) and the non-specific phosphodiesterase inhibitor IBMX (3-isobutyl-1-methylxanthine; final concentration 1 mM) were added. After 60 min the fluorescence transfer, which correlates with the amount of remaining cAMP, was measured with a microplate reader (Rubystar, BMG) at λex=337 nm, λem=620 nm and λem=665 nm. The enzyme activity was calculated from the quotient formed from the measured signal at 665 nm and that at 620 nm. The result was expressed as the percentage inhibition of enzyme activity of the control (without PDE4 inhibitor). The enzyme was omitted for measurement of the basal control.[N. Saldou et al., Comparison of recombinant human PDE4 isoforms: interaction with substrate and inhibitors, Cell. Signal. Vol. 10, No. 6, 427-440, 1998]. |
| Affinity data for this assay | |
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