[en] The first committed step in the biosynthesis of L-ascorbate from D-glucose in plants requires conversion of GDP-L-galactose to L-galactose 1-phosphate by a previously unidentified enzyme. Here we show that the protein encoded by VTC2, a gene mutated in vitamin C-deficient Arabidopsis thaliana strains, is a member of the GalT/Apa1 branch of the histidine triad protein superfamily that catalyzes the conversion of GDP-L-galactose to L-galactose 1-phosphate in a reaction that consumes inorganic phosphate and produces GDP. In characterizing recombinant VTC2 from A. thaliana as a specific GDP-L-galactose/GDP-D-glucose phosphorylase, we conclude that enzymes catalyzing each of the ten steps of the Smirnoff-Wheeler pathway from glucose to ascorbate have been identified. Finally, we identify VTC2 homologs in plants, invertebrates, and vertebrates, suggesting that a similar reaction is used widely in nature.
Disciplines :
Biochemistry, biophysics & molecular biology
Identifiers :
UNILU:UL-ARTICLE-2012-556
Author, co-author :
Linster, Carole ; University of Luxembourg > Luxembourg Centre for Systems Biomedicine (LCSB)
Gomez, Tara A.
Christensen, Kathryn C.
Adler, Lital N.
Young, Brian D.
Brenner, Charles
Clarke, Steven G.
Language :
English
Title :
Arabidopsis VTC2 encodes a GDP-L-galactose phosphorylase, the last unknown enzyme in the Smirnoff-Wheeler pathway to ascorbic acid in plants
Publication date :
29 June 2007
Journal title :
Journal of Biological Chemistry
ISSN :
1083-351X
Publisher :
American Society for Biochemistry and Molecular Biology, Baltimore, United States - Maryland