IUBMB Enzyme Nomenclature


Accepted name: mannuronan 5-epimerase

Reaction: [mannuronan]-β-D-mannuronate = [alginate]-α-L-guluronate

Glossary: mannuronan = a linear polymer of β-D-mannuronate residues linked by (1-4) linkages
alginate = a linear polymer of β-D-mannuronate residues linked by (1-4) linkages, with variable amounts of its C-5 epimer α-L-glucuronate.

Other name(s): algG (gene name); alginate epimerase; C5-mannuronan epimerase; mannuronan C-5-epimerase

Systematic name: [mannuronan]-β-D-mannuronate 5-epimerase

Comments: The enzyme epimerizes the C-5 bond in some β-D-mannuronate residues in mannuronan, converting them to α-L-guluronate residues, and thus modifying the mannuronan into alginate. It is found in brown algae and alginate-producing bacterial species from the Pseudomonas and Azotobacter genera.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number:


1. Franklin, M.J., Chitnis, C.E., Gacesa, P., Sonesson, A., White, D.C. and Ohman, D.E. Pseudomonas aeruginosa AlgG is a polymer level alginate C5-mannuronan epimerase. J. Bacteriol. 176 (1994) 1821-1830. [PMID: 8144447]

2. Morea, A., Mathee, K., Franklin, M.J., Giacomini, A., O'Regan, M. and Ohman, D.E. Characterization of algG encoding C5-epimerase in the alginate biosynthetic gene cluster of Pseudomonas fluorescens. Gene 278 (2001) 107-114. [PMID: 11707327]

3. Nyvall, P., Corre, E., Boisset, C., Barbeyron, T., Rousvoal, S., Scornet, D., Kloareg, B. and Boyen, C. Characterization of mannuronan C-5-epimerase genes from the brown alga Laminaria digitata. Plant Physiol. 133 (2003) 726-735. [PMID: 14526115]

4. Jain, S., Franklin, M.J., Ertesvag, H., Valla, S. and Ohman, D.E. The dual roles of AlgG in C-5-epimerization and secretion of alginate polymers in Pseudomonas aeruginosa. Mol. Microbiol. 47 (2003) 1123-1133. [PMID: 12581364]

5. Douthit, S.A., Dlakic, M., Ohman, D.E. and Franklin, M.J. Epimerase active domain of Pseudomonas aeruginosa AlgG, a protein that contains a right-handed β-helix. J. Bacteriol. 187 (2005) 4573-4583. [PMID: 15968068]

6. Wolfram, F., Kitova, E.N., Robinson, H., Walvoort, M.T., Codee, J.D., Klassen, J.S. and Howell, P.L. Catalytic mechanism and mode of action of the periplasmic alginate epimerase AlgG. J. Biol. Chem. 289 (2014) 6006-6019. [PMID: 24398681]

[EC created 2015]

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