Autotaxin (ATX, Ectonucleotide Pyrophosphatase/Phosphodiesterase-2, ENPP-2, Lysophospholipase D) is a secreted lysophospholipase D that catalyzes the hydrolysis of lysophosphatidylcholine (LPC) to generate lysophosphatidic acid (LPA). LPA is a lipid mediator that activates G protein-coupled receptors and induces a variety of biological responses, such as neurogenesis, angiogenesis, smooth-muscle contraction, platelet aggregation, and wound healing. ATX-LPA signaling is involved in a range of pathologies including tumor progression and inflammation. Cayman’s Autotaxin Inhibitor Screening Assay provides a convenient method for screening human ATX inhibitors. ATX cleaves bis-(p-nitrophenyl) phosphate liberating p-nitrophenol, a yellow product that is measured at 405-415 nm.