Reference : Impact of oxidative stress on ascorbate biosynthesis in Chlamydomonas via regulation ...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
Impact of oxidative stress on ascorbate biosynthesis in Chlamydomonas via regulation of the VTC2 gene encoding a GDP-L-galactose phosphorylase
Urzica, E. I. [> >]
Adler, Lital N. [> >]
Page, M. D. [> >]
Linster, Carole mailto [University of Luxembourg > Luxembourg Centre for Systems Biomedicine (LCSB) > >]
Arbing, M. A. [> >]
Casero, D. [> >]
Pellegrini, M. [> >]
Merchant, S. S. [> >]
Clarke, S. G. [> >]
Journal of Biological Chemistry
American Society for Biochemistry and Molecular Biology
Yes (verified by ORBilu)
[en] The L-galactose (Smirnoff-Wheeler) pathway represents the major route to L-ascorbic acid (vitamin C) biosynthesis in higher plants. Arabidopsis thaliana VTC2 and its paralogue VTC5 function as GDP-L-galactose phosphorylases converting GDP-L-galactose to L-galactose-1-P, thus catalyzing the first committed step in the biosynthesis of L-ascorbate. Here we report that the L-galactose pathway of ascorbate biosynthesis described in higher plants is conserved in green algae. The Chlamydomonas reinhardtii genome encodes all the enzymes required for vitamin C biosynthesis via the L-galactose pathway. We have characterized recombinant C. reinhardtii VTC2 as an active GDP-L-galactose phosphorylase. C. reinhardtii cells exposed to oxidative stress show increased VTC2 mRNA and L-ascorbate levels. Genes encoding enzymatic components of the ascorbate-glutathione system (e.g. ascorbate peroxidase, Mn superoxide dismutase, dehydroascorbate reductase) are also up-regulated in response to increased oxidative stress. These results indicate that C. reinhardtii VTC2, like its plant homologs, is a highly regulated enzyme in ascorbate biosynthesis in green algae and that, together with the ascorbate recycling system, the L-galactose pathway represents the major route for providing protective levels of ascorbate in oxidatively stressed algal cells.

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