Genetic evidence for the role of GDP-mannose in plant ascorbic acid (vitamin C) biosynthesis

Conklin, Patricia L.; Norris, Susan R.; Wheeler, Glen; Williams, Liz; Smirnoff, Nicholas

doi:10.1073/pnas.96.7.4198

Cited by 365 publications

(318 citation statements)

References 41 publications

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“…In marked contrast to the lethality caused by cyt1 mutations, vtc1 plants are viable and fertile, indicating that the vtc1 mutation is weak. Consistently, GMPP activity is reduced but not absent from vtc1 protein extracts (11).…”

Section: Map-based Cloning Of the Pmm-12supporting

confidence: 52%

“…Therefore, we measured AsA levels in pmm-12 after transfer to restrictive temperature, using the ascorbate-deficient vtc1 mutant (11,12) as a reference. In wild type plants, AsA levels increased significantly after transfer to 28°C, whereas in pmm-12 plants they remained relatively stable and amounted to only 20 -50% of wild type levels.…”

Section: Identification Of a Ts Cell Deathmentioning

confidence: 99%

“…1). As a consequence, vtc1 plants contain only ϳ25% of wild type AsA levels (11,12). Very recently, evidence has been provided for the role of PMM in AsA biosynthesis in plants (3).…”

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confidence: 99%

“…The AsA deficiency of the Arabidopsis thaliana vitamin c1 (vtc1) mutant demonstrated that GDP-mannose is also involved in the biosynthesis of AsA (11). The VTC1 locus encodes a GDP-mannose pyrophosphorylase (GMPP), the enzyme that produces GDP-mannose from mannose 1-phos-phate and acts immediately downstream of PMM (Fig.…”

mentioning

confidence: 99%

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A Temperature-sensitive Mutation in the Arabidopsis thaliana Phosphomannomutase Gene Disrupts Protein Glycosylation and Triggers Cell Death

Hoeberichts

Vaeck

Kiddle

et al. 2008

Journal of Biological Chemistry

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Eukaryotic phosphomannomutases (PMMs) catalyze the interconversion of mannose 6-phosphate to mannose 1-phosphate and are essential to the biosynthesis of GDP-mannose. As such, plant PMMs are involved in ascorbic acid (AsA) biosynthesis and N-glycosylation. We report on the conditional phenotype of the temperature-sensitive Arabidopsis thaliana pmm-12 mutant. Mutant seedlings were phenotypically similar to wild type seedlings when grown at 16 -18°C but died within several days after transfer to 28°C. This phenotype was observed throughout both vegetative and reproductive development. Protein extracts derived from pmm-12 plants had lower PMM protein and enzyme activity levels. In vitro biochemical analysis of recombinant proteins showed that the mutant PMM protein was compromised in its catalytic efficiency (K cat /K m ). Despite significantly decreased AsA levels in pmm-12 plants, AsA deficiency could not account for the observed phenotype. Since, at restrictive temperature, total glycoprotein patterns were altered and glycosylation of protein-disulfide isomerase was perturbed, we propose that a deficiency in protein glycosylation is responsible for the observed cell death phenotype.

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Section: Map-based Cloning Of the Pmm-12supporting

confidence: 52%

Section: Identification Of a Ts Cell Deathmentioning

confidence: 99%

“…1). As a consequence, vtc1 plants contain only ϳ25% of wild type AsA levels (11,12). Very recently, evidence has been provided for the role of PMM in AsA biosynthesis in plants (3).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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A Temperature-sensitive Mutation in the Arabidopsis thaliana Phosphomannomutase Gene Disrupts Protein Glycosylation and Triggers Cell Death

Hoeberichts

Vaeck

Kiddle

et al. 2008

Journal of Biological Chemistry

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“…VTC1 encodes GDP-mannose pyrophosphorylase (12), whereasVTC4 encodes L-Gal-1-P 3 phosphatase (8). In 2007 the VTC2 gene product was identified as the enzyme that produces L-Gal-1-P from GDP-L-galactose, which completed the characterization of the 10 enzymatic steps leading from D-glucose to L-ascorbic acid (13,14).…”

mentioning

confidence: 99%

A Second GDP-l-galactose Phosphorylase in Arabidopsis en Route to Vitamin C

Linster¹,

Adler²,

Webb³

et al. 2008

Journal of Biological Chemistry

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The Arabidopsis thaliana VTC2 gene encodes an enzyme that catalyzes the conversion of GDP-L-galactose to L-galactose 1-phosphate in the first committed step of the SmirnoffWheeler pathway to plant vitamin C synthesis. Mutations in VTC2 had previously been found to lead to only partial vitamin C deficiency. Here we show that the Arabidopsis gene At5g55120 encodes an enzyme with high sequence identity to VTC2. Designated VTC5, this enzyme displays substrate specificity and enzymatic properties that are remarkably similar to those of VTC2, suggesting that it may be responsible for residual vitamin C synthesis in vtc2 mutants. The exact nature of the reaction catalyzed by VTC2/VTC5 is controversial because of reports that kiwifruit and Arabidopsis VTC2 utilize hexose 1-phosphates as phosphorolytic acceptor substrates. Using liquid chromatography-mass spectroscopy and a VTC2-H238N mutant, we provide evidence that the reaction proceeds through a covalent guanylylated histidine residue within the histidine triad motif. Moreover, we show that both the Arabidopsis VTC2 and VTC5 enzymes catalyze simple phosphorolysis of the guanylylated enzyme, forming GDP and L-galactose 1-phosphate from GDP-L-galactose and phosphate, with poor reactivity of hexose 1-phosphates as phosphorolytic acceptors. Indeed, the endogenous activities from Japanese mustard spinach, lemon, and spinach have the same substrate requirements. These results show that Arabidopsis VTC2 and VTC5 proteins and their homologs in other plants are enzymes that guanylylate a conserved active site His residue with GDP-L-galactose, forming L-galactose 1-phosphate for vitamin C synthesis, and regenerate the enzyme with phosphate to form GDP.Vitamin C (L-ascorbic acid) is the most abundant soluble antioxidant in plants, in which it plays crucial roles in protection against oxidative damage and is used as a cofactor for several enzymes. It is synthesized via reactions initially proposed by Wheeler et al. (1) that are distinct from those used in vitamin C biosynthesis in animals. Although the Smirnoff-Wheeler pathway, arising from GDP-D-mannose and involving L-galactose formation, might not be the only route to vitamin C biosynthesis in plants (alternative pathways arising from myo-inositol and methylgalacturonate or involving L-gulose formation have been proposed; for reviews, see Refs. 2 and 3), it is undoubtedly the pathway that has received the strongest biochemical and genetic support in recent years (4 -9).Of the four loci (VTC1-4) that have been found to be mutated in vitamin C-deficient Arabidopsis thaliana plants (10, 11), three are now known to encode enzymes involved in the Smirnoff-Wheeler pathway. VTC1 encodes GDP-mannose pyrophosphorylase (12), whereasVTC4 encodes L-Gal-1-P 3 phosphatase (8). In 2007 the VTC2 gene product was identified as the enzyme that produces L-Gal-1-P from GDP-L-galactose, which completed the characterization of the 10 enzymatic steps leading from D-glucose to L-ascorbic acid (13,14). VTC2 is a member of the D-galactose-1-phosphate ...

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PlantL-ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing

Davey

Montagu

Inzé

et al. 2000

J. Sci. Food Agric.

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173

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Humans are unable to synthesise L‐ascorbic acid (L‐AA, ascorbate, vitamin C), and are thus entirely dependent upon dietary sources to meet needs. In both plant and animal metabolism, the biological functions of L‐ascorbic acid are centred around the antioxidant properties of this molecule. Considerable evidence has been accruing in the last two decades of the importance of L‐AA in protecting not only the plant from oxidative stress, but also mammals from various chronic diseases that have their origins in oxidative stress. Evidence suggests that the plasma levels of L‐AA in large sections of the population are sub‐optimal for the health protective effects of this vitamin. Until quite recently, little focus has been given to improving the L‐AA content of plant foods, either in terms of the amounts present in commercial crop varieties, or in minimising losses prior to ingestion. Further, while L‐AA biosynthesis in animals was elucidated in the 1960s,1 it is only very recently that a distinct biosynthetic route for plants has been proposed.2 The characterisation of this new pathway will undoubtedly provide the necessary focus and impetus to enable fundamental questions on plant L‐AA metabolism to be resolved. This review focuses on the role of L‐AA in metabolism and the latest studies regarding its biosynthesis, tissue compartmentalisation, turnover and catabolism. These inter‐relationships are considered in relation to the potential to improve the L‐AA content of crops. Methodology for the reliable analysis of L‐AA in plant foods is briefly reviewed. The concentrations found in common food sources and the effects of processing, or storage prior to consumption are discussed. Finally the factors that determine the bioavailability of L‐AA and how it may be improved are considered, as well as the most important future research needs. © 2000 Society of Chemical Industry

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Genetic evidence for the role of GDP-mannose in plant ascorbic acid (vitamin C) biosynthesis

Cited by 365 publications

References 41 publications

A Temperature-sensitive Mutation in the Arabidopsis thaliana Phosphomannomutase Gene Disrupts Protein Glycosylation and Triggers Cell Death

A Temperature-sensitive Mutation in the Arabidopsis thaliana Phosphomannomutase Gene Disrupts Protein Glycosylation and Triggers Cell Death

A Second GDP-l-galactose Phosphorylase in Arabidopsis en Route to Vitamin C

PlantL-ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing

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