DPP4/CD26 is a type II transmembrane glycoprotein expressed ubiquitously in most tissues and different cell types. The protein has a short cytoplasmic domain, transmembrane domain, a flexible stalk fragment and extracellular fragment. Both the catalytic peptide hydrolase domain and the beta-propeller ligand binding domain are located in the extracellular fragment. DPP4/CD26 is a multifunctional protein that exists in both a membrane bound form as well as an extracellular soluble form. As a peptidase, it removes N-terminal dipeptides sequentially from proteins with a proline or alanine as the penultimate P1 amino acid. DPP4/CD26 has been shown to cleave a wide range of substrates including GLP-1, BNP, etc. In addition to its peptidase activity, DPP4/CD26 interacts with multiple important cell surface ligands, such as adenosine deaminase, fibronectin, and IGF2 receptor to influence processes like T cell activation, cell migration and proliferation.
