Assay Method Information

Assay Name:  Transamidation Assay for Determining Inhibitor Selectivity
Description:  The most relevant off-targets are the transglutaminase isoenzymes especially tissue transglutaminase (TG2) because the enzyme is ubiquitously expressed throughout the human body. To determine selectivity, the fluorescence increase upon transglutaminase-catalyzed incorporation of dansylcadaverine into the universal transglutaminase substrate N,N-dimethylcasein was used (Lorand L, Lockridge O M, Campbell L K, Myhrman R, Bruner-Lorand J. Transamidating enzymes. Anal Biochem 1971; 44: 221-31.).Briefly, 15 μL of recombinant transglutaminase enzyme[5] [15 μg/mL hTG1 (T035, Zedira), 69 μg/mL hTG2 (T022), 29 μg/mL hTG6 (T021), 18 μg/mL hTG7 (T011)] were mixed with 270 μL assay buffer containing dansylcadaverine and N,N-dimethyl casein. In the case of FXIII, 12 μL cFXIII (25 μg/mL) and 3 μL human α-thrombin (0.5 U/mL, T056, Zedira) were mixed with 270 μL assay buffer. The mixture was incubated for 20 min at room temperature to activate FXIII. In the case of TG3 78 μg hTG3 (T024) were activated using 14 μg dispase II (Roche, Mannheim, Germany) in the presence of 1.4 mM CaCl2) and incubated for 30 min at 25 C. The activated hTG3 was subsequently assayed as described above. 15 μL of inhibitor solution dissolved in DMSO/assay buffer were added, mixed and the kinetic measurement started after 3 min. Fluorescence emission was continuously monitored for 30 min at 500 nm (λex=330 nm) and 37 C. using the CLARIOstar fluorescence plate reader. All measurements were performed in triplicate. The respective IC50 values were calculated by non-linear regression using the MARS software package (BMG Labtech, Ortenberg, Germany).
Affinity data for this assay
 

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