Farnesyl Transferase (EC 184.108.40.206) (FTase) catalyzes the transfer of a farnesyl isoprenyl group to a cysteine residue fourth from the C-terminus of certain proteins, such as Ras, Rho, Rab, other Ras-related small GTP-binding proteins, and other targets. The enzyme is a zinc metalloenzyme that requires Mg2+ for activity. Based on a literature search, a dansyl peptide of the form Dansyl-KTCXXX was selected for further work. The Km for our selected Dansyl peptide was determined to be 1.14 µM in the presence of 80 nM enzyme. DMSO tolerance studies indicated that DMSO concentrations >1 v% should be avoided. The IC50 of rat FTase for Lonafarnib was determined to be 25.6 nM under the conditions of the assay (10 µM Dansyl peptide, 20 µM Farnsyl Pyrophosphate, and 80 nM FTase).
Lonafarnib IC50 Determination
To test the suitability of BioAssay System’s Farnesyl Transferase Assay for screening for inhibitors, we performed an initial experiment with a known Farnesyl Transferase inhibitor, Lonafarnib, at 80 nM rat Farnesyl Transferase. Using 10 µM Dansyl substrate and 20 µM Farnesyl Pyrophosphate, we observed an IC50 of 25.6 nM for Lonafarnib. The percent enzyme activity was plotted versus the concentration of Lonafarnib.