The Enzyme Database

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Accepted name: GDP-mannose 3,5-epimerase
Reaction: (1) GDP-α-D-mannose = GDP-β-L-galactose
(2) GDP-α-D-mannose = GDP-β-L-gulose
Other name(s): GME (gene name); GDP-D-mannose:GDP-L-galactose epimerase; guanosine 5′-diphosphate D-mannose:guanosine 5′-diphosphate L-galactose epimerase
Systematic name: GDP-α-D-mannose 3,5-epimerase
Comments: The enzyme catalyses the formation of the stable intermediate GDP-β-L-gulose as well as GDP-β-L-galactose. The reaction proceeds by C4′ oxidation of GDP-α-D-mannose followed by epimerization of the C5′ position to give GDP-β-L-4-dehydro-gulose. This intermediate is either reduced to give GDP-β-L-gulose or the C3′ position is epimerized to give GDP-β-L-4-dehydro-galactose, followed by C4′ reduction to yield GDP-β-L-galactose. Both products serve as intermediates in two different variants of plant L-ascorbate biosynthesis pathways.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 72162-82-4
1.  Hebda, P.A., Behrman, E.J. and Barber, G.A. The guanosine 5′-diphosphate D-mannose: guanosine 5′-diphosphate L-galactose epimerase of Chlorella pyrenoidosa. Chemical synthesis of guanosine 5′-diphosphate L-galactose and further studies of the enzyme and the reaction it catalyzes. Arch. Biochem. Biophys. 194 (1979) 496–502. [DOI] [PMID: 443816]
2.  Barber, G.A. and Hebda, P.A. GDP-D-mannose: GDP-L-galactose epimerase from Chlorella pyrenoidosa. Methods Enzymol. 83 (1982) 522–525. [PMID: 7098948]
3.  Wolucka, B.A., Persiau, G., Van Doorsselaere, J., Davey, M.W., Demol, H., Vandekerckhove, J., Van Montagu, M., Zabeau, M. and Boerjan, W. Partial purification and identification of GDP-mannose 3",5"-epimerase of Arabidopsis thaliana, a key enzyme of the plant vitamin C pathway. Proc. Natl. Acad. Sci. USA 98 (2001) 14843–14848. [PMID: 11752432]
4.  Major, L.L., Wolucka, B.A. and Naismith, J.H. Structure and function of GDP-mannose-3′,5′-epimerase: an enzyme which performs three chemical reactions at the same active site. J. Am. Chem. Soc. 127 (2005) 18309–18320. [PMID: 16366586]
5.  Watanabe, K., Suzuki, K. and Kitamura, S. Characterization of a GDP-D-mannose 3′′,5′′-epimerase from rice. Phytochemistry 67 (2006) 338–346. [PMID: 16413588]
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