Journal: Febs Letters
Article Title: The Caenorhabditis elegans DPF ‐3 and human DPP4 have tripeptidyl peptidase activity
doi: 10.1002/1873-3468.70219
Figure Lengend Snippet: Enzyme activity profiles of DPPIV family proteases. (A) To compare the peptidase activities of hDPP4, hDPP9, C. elegans DPF‐3, and the catalytic mutant DPF‐3 (S784A), the fluorogenic tripeptide substrate H‐Met‐Gly‐Pro‐AMC was used over a range of concentrations (0.5–64 μ m ). hDPP4 displayed robust, concentration‐dependent activity, reaching 100% normalized fluorescence at 64 μ m substrate. In contrast, wild‐type DPF‐3 showed substantially lower activity, achieving only ~25% of the maximal signal at the highest substrate concentration. hDPP9 activity was negligible under these conditions, and the S784A mutation abrogated DPF‐3 activity completely, confirming loss of catalytic function. (B, C) Michaelis–Menten analysis of DPF‐3 (B) and hDPP4 (C) revealed distinct kinetic parameters. Nonlinear regression yielded for DPF‐3 a V max of 33 193 AU min −1 and a K m of 245.6 μ m . hDPP4 exhibited a higher catalytic efficiency, with V max = 56 027 AU min −1 and K m = 461.5 μ m . The higher V max of hDPP4, despite its higher K m , underscores its greater turnover capacity on this substrate. (D, E) Dose–response curves for the hDPP8/9 inhibitor 1G244 and the hDPP4 inhibitor vildagliptin were generated against DPF‐3 and hDPP4 using substrate concentrations near each enzyme's K m . For DPF‐3, 1G244 inhibited activity with an IC 50 = 499.5 n m , whereas vildagliptin was more potent (IC 50 = 142.1 n m ) (D). DPP4 was more sensitive to both 1G244 (IC 50 = 43.3 n m ) and vildagliptin (IC 50 = 14.8 n m ) (E), indicating differential inhibitor specificities within the DPPIV family. Each graph represents the mean data from triplicate experiments, and the error bars represent the standard deviation.
Article Snippet: Enzymatic activities of hDPP4 and DPF‐3 were measured using the fluorogenic tripeptide substrate H‐Met‐Gly‐Pro‐AMC (7‐amino‐4‐methylcoumarin, Catalog number: ES017, R&D Systems).
Techniques: Activity Assay, Mutagenesis, Concentration Assay, Fluorescence, Generated, Standard Deviation
