Biosynthesis of dermatan sulfate: chondroitin-glucuronate C5-epimerase is identical to SART2.

Abstract

We identified the gene encoding chondroitin-glucuronate C5-epimerase (EC 5.1.3.19) that converts D-glucuronic acid to L-iduronic acid residues in dermatan sulfate biosynthesis. The enzyme was solubilized from bovine spleen, and an approximately 43,000-fold purified preparation containing a major 89-kDa candidate component was subjected to mass spectrometry analysis of tryptic peptides. SART2 (squamous cell carcinoma antigen recognized by T cell 2), a protein with unknown function highly expressed in cancer cells and tissues, was identified by 18 peptides covering 26% of the sequence. Transient expression of cDNA resulted in a 22-fold increase in epimerase activity in 293HEK cell lysate. Moreover, overexpressing cells produced dermatan sulfate chains with 20% of iduronic acid-containing disaccharide units, as compared with 5% for mock-transfected cells. The iduronic acid residues were preferentially clustered in blocks, as in naturally occurring dermatan sulfate. Given the discovered identity, we propose to rename SART2 (Nakao, M., Shichijo, S., Imaizumi, T., Inoue, Y., Matsunaga, K., Yamada, A., Kikuchi, M., Tsuda, N., Ohta, K., Takamori, S., Yamana, H., Fujita, H., and Itoh, K. (2000) J. Immunol. 164, 2565-2574) with a functional designation, chondroitin-glucuronate C5-epimerase (or DS epimerase). DS epimerase activity is ubiquitously present in normal tissues, although with marked quantitative differences. It is highly homologous to part of the NCAG1 protein, encoded by the C18orf4 gene, genetically linked to bipolar disorder. NCAG1 also contains a putative chondroitin sulfate sulfotransferase domain and thus may be involved in dermatan sulfate biosynthesis. The functional relation between dermatan sulfate and cancer is unknown but may involve known iduronic acid-dependent interactions with growth factors, selectins, cytokines, or coagulation inhibitors.

• Authors: Marco Maccarana, Benny Olander, Johan Malmström, Kerstin Tiedemann, Ruedi Aebersold, Ulf Lindahl, Jin-Ping Li, Anders Malmström
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 281 Issue 17 Pg. 11560-8 (Apr 28 2006) ISSN: 0021-9258 [Print] United States
• PMID: 16505484 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, Neoplasm
• DNA, Complementary
• DNA-Binding Proteins
• Neoplasm Proteins
• Dermatan Sulfate
• Iduronic Acid
• Carbohydrate Epimerases
• chondroitin D-glucuronosyl 5-epimerase
• DSE protein, human

Topics

• Amino Acid Sequence
• Animals
• Antigens, Neoplasm (chemistry, metabolism)
• Carbohydrate Epimerases (genetics, isolation & purification, metabolism)
• Cattle
• Cells, Cultured
• DNA, Complementary
• DNA-Binding Proteins (chemistry, metabolism)
• Dermatan Sulfate (biosynthesis)
• Humans
• Iduronic Acid (metabolism)
• Kidney (metabolism)
• Mass Spectrometry
• Molecular Sequence Data
• Muscles (metabolism)
• Neoplasm Proteins (chemistry, metabolism)
• Rats
• Sequence Homology, Amino Acid
• Spleen (enzymology)