||Gly-Pro-AMC is a sensitive fluorogenic substrate for detecting dipeptidyl peptidase IV (DPPIV), a serine protease that cleaves N-terminal dipeptides from polypeptides with L-proline or L-alanine at the penultimate position. DPPIV is a multifunctional protein expressed on the surface of several cell types including epithelial, endothelial and lymphoid cells. It is identical to the T cell activation antigen CD26 and the adenosine deaminase binding protein, and it is also released as a soluble form in plasma. The substrates of CD26/DPPIV include a wide variety of proline-containing peptides such as growth factors, chemokines, neuropeptides, and vasoactive peptides. DPPIV is involved in immune regulation, signal transduction, and apoptosis, and appears to play an important role in tumor progression. Importantly, DPPIV is a therapeutic target for type II diabetes due to its role as a serum protease that cleaves incretin hormones of the glucagon family of peptides and thus regulates glucose homeostasis . Studies indicate that a DPPIV inhibitor improves impaired glucose tolerance. The assay of DPPIV with Gly-Pro-AMC is a simple, fast and flexible assay that is ideal for high-through put screening. The assay demonstrates improved sensitivity compared to colorimetric DPPIV assays, allowing the researcher to use less enzyme while still achieving appropriate Z-values. The homogeneous coupled-enzyme format is convenient, requiring only a single reagent addition to the test samples. Maximal sensitivity is achieved in 20-30 minutes, and the signal generated is very stable.