| Assay Method Information | |
| | Fluorometric Assay |
| Description: | A continuous fluorometric assay is employed with the substrate Gly-Pro-AMC, which is cleaved by DPP-4 to release the fluorescent AMC leaving group. The kinetic parameters that describe this reaction are as follows: Km=50 uM; kcat=75 s-1; kcat/Km=1.5x106 M-1s-1. A typical reaction contains approximately 50 pM enzyme, 50 uM Gly-Pro-AMC, and buffer (100 mM HEPES, pH 7.5, 0.1 mg/ml BSA) in a total reaction volume of 100 uL. Liberation of AMC is monitored continuously in a 96-well plate fluorometer using an excitation wavelength of 360 nm and an emission wavelength of 460 nm. Under these conditions, approximately 0.8 uM AMC is produced in 30 minutes at 25 degrees C. The enzyme used in these studies was soluble (transmembrane domain and cytoplasmic extension excluded) human protein produced in a baculovirus expression system (Bac-To-Bac, Gibco BRL). The kinetic constants for hydrolysis of Gly-Pro-AMC and GLP-1 were found to be in accord with literature values for the native enzyme. To measure the dissociation constants for compounds, solutions of inhibitor in DMSO were added to reactions containing enzyme and substrate (final DMSO concentration is 1%). All experiments were conducted at room temperature using the standard reaction conditions described above. |
| Affinity data for this assay | |
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