L-Ascorbate biosynthesis in higher plants: the role of VTC2.
In the past year, the last missing enzyme of the L-galactose pathway, the linear form of which appears to represent the major biosynthetic route to L-ascorbate (vitamin C) in higher plants, has been identified as a GDP-L-galactose phosphorylase. This enzyme catalyzes the first committed step in the synthesis of that vital antioxidant and enzyme cofactor. Here, we discuss how GDP-L-galactose phosphorylase enzymes, encoded in Arabidopsis by the paralogous VTC2 and VTC5 genes, function in concert with the other enzymes of the L-galactose pathway to provide plants with the appropriate levels of L-ascorbate. We hypothesize that regulation of L-ascorbate biosynthesis might occur at more than one step and warrants further investigation to allow for the manipulation of vitamin C levels in plants.
Linster
Carole L
CL
Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095, USA.
Clarke
Steven G
SG
D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000096:biosynthesis*; D005690:Galactose / Q000378:metabolism; D017343:Genes, Plant; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology / Q000378:metabolism*; D018724:Spinacia oleracea / Q000201:enzymology / Q000378:metabolism; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase / Q000378:metabolism
D000975:Antioxidants; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase; D010744:Phosphoric Monoester Hydrolases; D001205:Ascorbic Acid; D005690:Galactose