GLCE (glucuronic acid epimerase), also known as HSEPI (heparin/heparan sulfate:glucuronic acid C5-epimerase) or D-glucuronyl C5-epimerase, is a single-pass type II membrane protein that is part of the golgi apparatus and, through its enzymatic activity, is essential for proper biological function of heparan sulphate (HS). GLCE epimerizes D-glucuronic acid into L-iduronic acid of HS, thus changing the specificity of HS and allowing it to bind to cytokines and growth factors. GLCE is a target of the beta-catenin–TCF4 transactivation complex; an essential component in the Wnt/APC/beta-catenin signaling pathway that is upregulated in colon carcinoma cells. The enzymatic activity of GLCE is enhanced by overexpression of beta-catenin–TCF4, suggesting a possible role for GLCE in the dysregulation of proper signaling pathways; a dysregulation that leads to the development of human epithelial tumors.