Ecto-enzyme CD39 (ectonucleoside triphosphate diphosphohydrolase 1) is encoded by ETPD1 and is expressed by various immune and non-immune cells (e.g. fibroblasts and endothelial cells).1
- The function of CD39 is to hydrolyze extracellular adenosine triphosphate (eATP) to adenosine monophosphate (AMP) by removing up to two phosphate groups. AMP can then be converted to extracellular adenosine by CD73, also an ecto-enzyme.1
Extracellular ATP acts as a pro-inflammatory molecule and is actively released from activated or stressed cells during inflammation, hypoxia or apoptosis and passively from necrotic cells via rupture.2 eATP binds to purinergic (P2) receptors widely expressed on immune and non-immune cells which initiates signaling cascades resulting in calcium mobilization, actin polymerization, chemotaxis, release of mediators, cell maturation, cytotoxicity, and death to induce an immune response.3
Extraceullar adenosine has the opposite effect, producing anti-inflammatory effects by binding P1 receptors (A1, A2A, A2B, and A3) which are also widely expressed, especially on immune cells.2