The protein encoded by this gene is a tumor-rejection antigen. It is localized to the endoplasmic reticulum and functions to convert D-glucuronic acid to L-iduronic acid during the biosynthesis of dermatan sulfate. This antigen possesses tumor epitopes capable of inducing HLA-A24-restricted and tumor-specific cytotoxic T lymphocytes in cancer patients and may be useful for specific immunotherapy. Mutations in this gene cause inmusculocontractural Ehlers-Danlos syndrome. Alternative splicing results in multiple transcript variants. A related pseudogene has been identified on chromosome 9, and a paralogous gene exists on chromosome 18.