– ENPP5 is a member of the nucleotide pyrophosphatase/phosphodiesterase family (NPP). It is a family comprised of dimeric enzymes that catalyze the hydrolysis of phosphate diester bonds. There are seven isoforms in NPP family, some of which prefer nucleotide substrates, some of which prefer phospholipid substrates, and others of which prefer substrates that have not yet been determined. NPP also belongs to the alkaline phosphatase (AP) superfamily of enzymes and they are located in the cell membrane and hydrolyze extracellular phosphate diesters to affect a wide variety of biological processes. ENPP5 belongs to a group of nucleotidemetabolizing ectoenzymes, which regulate the availability of extracellular nucleotides. ENPP5 may play a role in neuronal cell communication. However, it lacks nucleotide pyrophosphatase and lysopholipase D activity. It may also be involved in neuronal cell communication. The amino acid sequence of human ENPP5 is 100%, 88%, and 82% identical to that of chimpanzee, dog and mouse/rat. ENPP5 functions in phospholipid metabolism.