Autotaxin

Autotaxin also known as ectonucleotide pyrophosphatase/phosphodiesterase family member 2 (E-NPP 2) is an is_associated_with::enzyme that in humans is encoded by the ENPP2 is_associated_with::gene.

Function
Autotaxin, also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (NPP2 or ENPP2), is a secreted enzyme important for generating the is_associated_with::lipid signaling molecule is_associated_with::lysophosphatidic acid (LPA). Autotaxin has lysois_associated_with::phospholipase D activity that converts lysois_associated_with::phosphatidylcholine into LPA.

Autotaxin was originally identified as a tumor cell-motility-stimulating factor; later it was shown to be LPA (which signals through is_associated_with::Lysophospholipid receptors), the lipid product of the reaction catalyzed by autotaxin, which is responsible for its effects on cell-proliferation.

The protein encoded by this gene functions as both a is_associated_with::phosphodiesterase, which cleaves phosphodiester bonds at the 5' end of oligonucleotides, and as a is_associated_with::phospholipase, which catalyzes production of lysophosphatidic acid (LPA) in extracellular fluids. LPA evokes growth factor-like responses including stimulation of cell proliferation and chemotaxis. This gene product stimulates the motility of tumor cells, has angiogenic properties, and its expression is upregulated in several kinds of carcinomas. The gene product is secreted and further processed to make the biologically active form. Several alternatively spliced transcript variants have been identified, but the full-length nature of only two transcript variants has been determined.

Structure
The crystal structures rat and mouse autotaxin have been solved. In each case, the is_associated_with::apo structure have been solved along with product or inhibitor bound complexes. Both proteins consist of 4 domains, 2 N-terminal somatomedin-B-like (SMB) domains which may be involved in cell-surface localisation. The catalytic domain follows and contains a deep hydrophobic pocket in which the lipid substrate binds. At the is_associated_with::C-terminus is the inactive nuclease domain which may function to aid protein stability.