Assay Method Information

Assay Name:  Biochemical Assay
Description:  USP25: The assay was performed in a final volume of 9 μL in assay buffer containing 20 mM Tris-HCl (pH 8.0, (1M Tris-HCl, pH 8.0 solution; Corning 46-031-CM)), 3 mM BME (2-Mercaptoethanol; Sigma 63689-25ML-F), 0.03% BGG (0.22 μM filtered. Sigma, G7516-25G), and 0.01% Triton X-100 (Sigma, T9284-10L). Nanoliter quantities of 10-point, 3-fold serial dilution in DMSO was pre-dispensed into 1536 assay plates (Corning, #3724BC) for a final test concentration of 25 μM to 1.3 nM, top to lowest dose, respectively. Enzyme USP25, construct USP25-His6, (Boston Biochem E-546). Concentration and incubation times were optimized for the maximal signal-to-background while maintaining initial velocity conditions at a fixed substrate concentration. The final concentration of the enzyme in the assay was 75 pM. Final substrate (Ub-Rh110 Ubiquitin-Rhodamine 110, R&D Systems # U-555) concentration was 25 nM with [Ub-Rh110]<<Km. 3 μL of 2× enzyme was added to assay plates (pre-stamped with compound) preincubated with USP25 for 30 minutes and then 3 μL of 2×Ub-Rh110 was added to assay plates. Plates were incubated for 45 minutes at room temperature before addition of 3 μL of stop solution (final concentration of 10 mM citric acid (Sigma, 251275-500G)). Fluorescence was read on the Envision (Excitation at 485 nm and Emission at 535 nm; Perkin Elmer) or on the PheraSTAR (Excitation at 485 nm and Emission at 535 nm; BMG Labtech).
Affinity data for this assay
 

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