| Assay Method Information | |
| | Activity Assay |
| Description: | The EGLN-1 (or EGLN-3) enzyme activity is determined using mass spectrometry (matrix-assisted laser desorption ionization, time-of-flight MS, MALDI-TOF MS. Recombinant human EGLN-1-179/426 is prepared as described above and in the Supplemental Data. Full-length recombinant human EGLN-3 is prepared in a similar way, however it is necessary to use the His-MBP-TVMV-EGLN-3 fusion for the assay due to the instability of the cleaved protein. For both enzymes, the HIF-1α peptide corresponding to residues 556-574 is used as substrate. The reaction is conducted in a total volume of 50 uL containing TrisCl (5 mM, pH 7.5), ascorbate (120 uM), 2-oxoglutarate (3.2 uM), HIF-1α (8.6 uM), and bovine serum albumin (0.01%). The enzyme, quantity predetermined to hydroxylate 20% of substrate in 20 minutes, is added to start the reaction. Where inhibitors are used, compounds are prepared in dimethyl sulfoxide at 10-fold final assay concentration. After 20 minutes at room temperature, the reaction is stopped by transferring 10 uL of reaction mixture to 50 uL of a mass spectrometry matrix solution (α-cyano-4-hydroxycinnamic acid, 5 mg/mL in 50% acetonitrile/0.1% TFA, 5 mM NH4PO4). Two microliters of the mixture is spotted onto a MALDI-TOF MS target plate for analysis with an Applied Biosystems (Foster City, Calif.) 4700 Proteomics Analyzer MALDI-TOF MS equipped with a Nd:YAG laser (355 nm, 3 ns pulse width, 200 Hz repetition rate). |
| Affinity data for this assay | |
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