Recombinant Mouse ENPP-4 Protein, CF

Ectonucleotide pyrophosphatase/phosphodiesterase 4 (ENPP-4 or NPP4) belongs to a group of ecto-enzymes which regulate the availability of extracellular nucleotides (1). This enzyme family forms a subgroup of a larger family that also includes arylsulfatases, phosphopentomutases, 2,3-bisphosphoglycerate-independent phosphoglycerate mutases (iPGM), and alkaline phosphatases (2). Mature mouse ENPP-4 consists of a 392 amino acid (aa) ectodomain that contains the catalytic domain with a zinc-coordinated substrate binding pocket, a 21 aa transmembrane segment, and a 25 aa cytoplasmic tail (3). It shares 86% and 90% aa sequence identity with human and rat ENPP-4, respectively. Alternative splicing generates a short isoform with a 32 aa deletion in the phosphodiesterase domain. ENPP-4 hydrolyzes phosphodiester bonds in nucleotides with a preference for adenine nucleotides (3). It cleaves the diadenosine compounds Ap3A and Ap4a which are released from the dense granules of thrombin-activated platelets (3, 4). These reactions generate AMP and ADP from Ap3A cleavage, and AMP and ATP from Ap4A cleavage (4). ENPP-4 is expressed on the surface of vascular endothelial cells where its activity prolongs platelet aggretation and contributes to thrombus formation (4).