B vitamin supply in plants and humans: the importance of vitamer homeostasis

Abstract

B vitamins are a group of water-soluble micronutrients that are required in all life forms. With the lack of biosynthetic pathways, humans depend on dietary uptake of these compounds, either directly or indirectly, from plant sources. B vitamins are frequently given little consideration beyond their role as enzyme accessory factors and are assumed not to limit metabolism. However, it should be recognized that each individual B vitamin is a family of compounds (vitamers), the regulation of which has dedicated pathways. Moreover, it is becoming increasingly evident that individual family members have physiological relevance and should not be sidelined. Here, we elaborate on the known forms of vitamins B 1 , B 6 and B 9 , their distinct functions and importance to metabolism, in both human and plant health, and highlight the relevance of vitamer homeostasis. Research on B vitamin metabolism over the past several years indicates that not only the total level of vitamins but also the oft-neglected homeostasis of the various vitamers of each B vitamin is essential to human and plant health. We briefly discuss the potential of plant biology studies in supporting human health regarding these B vitamins as essential micronutrients. Based on the findings of the past few years we conclude that research should focus on the significance of vitamer homeostasisat the organ, tissue and subcellular levelswhich could improve the health of not only humans but also plants, benefiting from cross-disciplinary approaches and novel technologies.

Variation of vitamin B contents in maize inbred lines: Potential genetic resources for biofortification

“…Vitamin B, specifically vitamers, and their homeostasis within the tissue, organ, and subcellular levels are essential for the improved health of both humans and plants (55,56). Not only as human food, but also as internal metabolites in plants, they play major physiological roles that include disease resistance [vitamin B6, tomato and Arabidopsis thaliana, (57)], a protective role against UV-B supporting peroxidase defense linked to the biosynthesis of PLP [Arabidopsis thaliana, (58)], tolerance to salinity (NaCl) or methyl viologen-induced stress [vitamin B6, potato, (59)] and drought [vitamin B3, Arabidopsis thaliana, (60)].…”

“…Humans rely on the dietary uptake of vitamin B, directly or indirectly, from plants, microbes, and animals. Among the dietary sources, maize, which is consumed as a staple food in several low and middle-income countries, has become an integrated part of their tradition and culture (55). Despite this, two billion people suffer from micronutrient deficiencies and have limited access to nutritious foods.…”

Preparatory work for the update of the tolerable upper intake levels for vitamin B6

“…Electrophiles are capable of directly or indirectly perturbing the structures and functions of macromolecules, e.g. proteins and DNA (Aitken et al, 2012;Liu et al, 2022). PLP is most relevant in this context, as PL is found in a hemiacetal form at neutral pH, i.e.…”

“…The liver is the principal site for re-phosphorylation, which is performed in hepatocytes by PLK for all vitamin B6 vitamers (PLPLP; PNPNP; PMPMP), where pyridoxine 5´-phosphate oxidase (PNPO) converts PNP and PMP to PLP (Hadtstein & Vrolijk, 2021;Liu et al, 2022). Although PLP is the principal active form of vitamin B6, PMP also acts as a cofactor in specific biochemical reactions (transamination) (Berger et al, 2022;Liu et al, 2022). As part of vitamin B6 metabolism, intracellular dephosphorylation within the liver also occurs, which is catalysed by the enzyme pyridoxal 5´-phosphate phosphatase (PDXP) (Gohla, 2019;Hadtstein & Vrolijk, 2021).…”

Dietary B vitamins and glioma: A case–control study based on Chinese population

“…B vitamins are a group of water-soluble micronutrients required by all forms of cellular life, from bacteria to humans (1). Unlike other nutrients, B vitamins are not classified based on chemical structural similarity but on their physiological functions in tissues and cells (2,3).…”