Calcium Activated Nucleotidase 1 (CANT1), is a Ca2+-dependent nucleoside diphosphatase which can hydrolyze a variety of nucleoside di- and triphosphates. CANT1 is also known as SCAN-1 and SHAPY. Its preferred substrates are UDP and GDP, and it is not active against nucleoside monophosphates (1). The CANT1 gene encodes a Type II membrane protein that is anchored in the endoplasmic reticulum (ER) membrane with its catalytic domain in the ER lumen (2). A secreted, soluble form of the enzyme also exists (1). CANT1 is expressed in many tissues, including fibroblasts and chondrocytes. Mutations of CANT1 are a cause of Desbuquois dysplasia, a condition characterized by deformation of bones and joints (2, 3). Recombinant human CANT1 was expressed as a secreted, soluble protein.