GDP-mannose 3,5-epimerase

In enzymology, a GDP-mannose 3,5-epimerase (EC 5.1.3.18) is an enzyme that catalyzes the chemical reaction

GDP-mannose ${\displaystyle \rightleftharpoons }$ GDP-L-galactose + GDP-L-gulose - initial reaction overview (updated in 2020, see below)

Hence, this enzyme has one substrate, GDP-mannose, and two products, and

Since only GDP-L-gulose (the C5-epimer of GDP-D-mannose) was found in the reaction mixture, it was postulated that the enzyme performs the C5-epimerization prior to the C3-epimerization. However, was recently found as a reaction product, which means that both reaction routes can occur: C5-prior-to-C3 and C3-prior-to-C5. This also means that the GDP-mannose 3,5-epimerase has three reaction products, namely the main product (C3,5-epimer) and two sideproducts (C5-epimer) + (C3-epimer).

GDP-D-mannose ${\displaystyle \rightleftharpoons }$ GDP-L-galactose (C3,5-epimer) + GDP-L-gulose (C5-epimer) + GDP-D-altrose (C3-epimer) - reaction overview update in 2020

This enzyme belongs to the family of isomerases, specifically those racemases and epimerases acting on carbohydrates and derivatives. The systematic name of this enzyme class is GDP-mannose 3,5-epimerase. Other names in common use include GDP-D-mannose:GDP-L-galactose epimerase, guanosine 5'-diphosphate D-mannose:guanosine 5'-diphosphate, and L-galactose epimerase. This enzyme participates in .

Structural studies[]

As of late 2007, 4 structures have been solved for this class of enzymes, with PDB accession codes 2C54, 2C59, 2C5A, and 2C5E.

References[]

• Barber GA, Hebda PA (1982). "GDP-D-mannose: GDP-L-galactose epimerase from Chlorella pyrenoidosa". Methods Enzymol. Methods in Enzymology. 83: 522–5. doi:10.1016/0076-6879(82)83046-2. ISBN 978-0-12-181983-5. PMID 7098948.
• Hebda PA, Behrman EJ, Barber GA (1979). "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 (2): 496–502. doi:10.1016/0003-9861(79)90644-1. PMID 443816.
• Gevaert O, Van Overtveldt S, Beerens K, Desmet T (2019). "Characterization of the First Bacterial and Thermostable GDP-Mannose 3,5-Epimerase". Int. J. Mol. Sci. 20 (14): E3530. doi:10.3390/ijms20143530. PMC 6678494. PMID 31330931.
• Gevaert O, Van Overtveldt S, Da Costa M, Beerens K, Desmet T (2020). "GDP-altrose as novel product of GDP-mannose 3,5-epimerase: Revisiting its reaction mechanism". Int J Biol Macromol. 165 (Pt B): 1862–1868. doi:10.1016/j.ijbiomac.2020.10.067. PMID 33075338.