The invertebrate Caenorhabditis elegans biosynthesizes ascorbate

Abstract

L-ascorbate, commonly known as vitamin C, serves as an antioxidant and cofactor essential for many biological processes. Distinct ascorbate biosynthetic pathways have been established for animals and plants, but little is known about the presence or synthesis of this molecule in invertebrate species. We have investigated ascorbate metabolism in the nematode Caenorhabditis elegans, where this molecule would be expected to play roles in oxidative stress resistance and as cofactor in collagen and neurotransmitter synthesis. Using high-performance liquid chromatography and gas-chromatography mass spectrometry, we determined that ascorbate is present at low amounts in the egg stage, L1 larvae, and mixed animal populations, with the egg stage containing the highest concentrations. Incubating C. elegans with precursor molecules necessary for ascorbate synthesis in plants and animals did not significantly alter ascorbate levels. Furthermore, bioinformatic analyses did not support the presence in C. elegans of either the plant or the animal biosynthetic pathway. However, we observed the complete 13C-labeling of ascorbate when C. elegans was grown with 13C-labeled Escherichia coli as a food source. These results support the hypothesis that ascorbate biosynthesis in invertebrates may proceed by a novel pathway and lay the foundation for a broader understanding of its biological role.

Metabolome and proteome changes with aging in Caenorhabditis elegans

“…In C. elegans ascorbate levels were highest in eggs, levels declined throughout larval growth, and were lowest in mixed age adults. In addition ascorbate levels were higher when worms were grown in liquid media compared to when they were cultured on agar plates, but ascorbate levels did not increase when worms were exposed to the free radical generator paraquat (Patananan et al 2015). We predict that the decreased level of galactonic acid-1,4-lactone with age is partially due to its conversion into ascorbate, as we measured ascorbate and DHA levels to increase during aging.…”

“…However, it is unknown if C. elegans can convert galactonic acid-1,4-lactone into ascorbate as bioinformatic analysis did not detect an L-galactonic acid-1,4-lactone dehydrogenase in the C. elegans genome (Patananan et al 2015), but invertebrates may have evolved a unique, as of yet unidentified enzyme to catalyze this reaction. In support of this hypothesis C. elegans has been shown to synthesize both ascorbate and an unidentified hydrogenated lactone precursor to ascorbate, but the ascorbate synthesis pathway appears to be different from the pathways present in animals, plants, or protists, while ascorbate is not synthesized by E. coli (Patananan et al 2015). In C. elegans ascorbate levels were highest in eggs, levels declined throughout larval growth, and were lowest in mixed age adults.…”

Vitamin B12 deficiency results in severe oxidative stress, leading to memory retention impairment in Caenorhabditis elegans

“…Recently, Alexander et al [36] reported that C. elegans can synthesize L -ascorbic acid de novo . L -ascorbic acid serves as a potent antioxidant and participates in collagen biosynthesis in most mammals [37], but the function of L -ascorbic acid in C. elegans is not understood.…”

Ascorbic acid metabolism and functions: A comparison of plants and mammals

“…Ascorbate biosynthesis pathways differ between animals, green plants and photosynthetic protists [2] , [62] while, as noted in the previous section, fungi synthesise a 5C analogue of ascorbate, D-erythroascorbate. Recent evidence suggests that the nematode Caenorhabditis elegans contains ascorbate but does not use any of the known pathways [63] . Ascorbate biosynthesis pathways have been well-reviewed [2] , [57] , [64] , [65] , [66] and recent developments are minimal, so they will only be outlined here ( Fig.…”