HS6ST3 (Heparin sulfate 6-O-sulfotransferase 3) is a 60-62kD member of the sulfotransferase 6 family of enzymes. It is one of three 6-O sulfotransferase isoforms, all of which essentially perform the same function, but all of which are the products of distinct genes. HS6ST3 is known to sulfate the #6 position of glucosamine sulfate that is linked to a 2-O-sulfated iduronic acid in heparin sulfate. The molecule shows a temporal expression pattern, being found in postnatal cerebellar Purkinje cells and cerebral cortical pyramidal cells in layers II/III and V. Mouse HS6ST3 is a 470aa type II transmembrane glycoprotein. It contains a short four aa cytoplasmic N-terminus coupled to an extended 443aa lumenal domain (aa28-470). The lumenal domain contains a stem region (aa28-83) that mediates oligomerization and Golgi localization, plus a sulfotransferase enzyme domain (aa142-409). Cleavage within the stem region by b-secretase generates a soluble form of HS6ST3. Over aa28-470, mouse HS6ST3 shares 99-95aa identity with rat and human HS6ST3, respectively.