Introduction

D-Pantothenic acid (D-PA;Figure 1), also known as vitamin B5, is an essential vitamin widely used in food, feed, chemical, and pharmaceutical industries. Pure D-pantothenic acid can be used as a dietary supplement: it is water-soluble,viscous, and yellow in color. Because D-pantothenic acid is relatively unstable - it can be destroyed by heat and acid and alkaline conditions - the more stable calcium pantothenate is the form of vitamin B5 usually found in dietary supplements. It is water-soluble, crystalline, and white in color. D-pantothenic acid functions as the essential precursor of acyl carrier protein (ACP) and coenzyme A (CoA). It is also involved in various metabolisms of sugar, fat and protein. Recently, the demand for D-pantothenic acid has gradually increased because of the rapid growth of the market for feed additives and drugs [2,3].Currently, the chemical condensation of D-pantolactone with β-alanine is the most widely used method for industrial production of D-pantothenic acid. D-pantolactone is mainly obtained by there solution of DL-pantolactone. However, the synthesis of raw material DL-pantolactone requires the use of highly toxic raw materials, such as hydrocyanic acid and sodium cyanide,accompanied by cyanide-containing wastewater pollution. The increase in environmental pollution has made the production of D-pantothenic acid by eco-friendly methods receive widespread attention from researchers [1-2]

Recently, a new microbial platform for producing D-PA has been established on the basis of D-PA biosynthetic pathway, particularly Escherichia coli or Corynebacterium glutamicum,which use sustainable raw materials, including glucose and other renewable carbohydrates,as substrates . As a commonly used host, E. coli has several advantages, such as higher productivity, lower culture cost, and easy development of high-productivity mutants.Therefore, E. coli has proven to be a potential host for the production of D-pantothenic acid [1].

The production of D-pantothenic acid from Escherichia coli

Escherichia coli was engineered to produce D-pantothenic acid via systematic metabolic engineering. Firstly, genes of acetohydroxy acid synthase II, pantothenate synthetase, 3-methyl-2-oxobutanoate hydroxymethyltransferase, 2-dehydropantoate 2-reductase and ketol-acid reductoisomerase were edited in E. coli W3110 with a resulting D-pantothenic acid yield of 0.49?g/L. Expressions of valine-pyruvate aminotransferase and branched-chain-amino-acid aminotransferase were then attenuated to decrease the carbon flux in l-valine biosynthetic pathway which is a competing pathway to the D-pantothenic acid biosynthetic pathway, and the yield increased to 1.48?g/L. Mutagenesis of pantothenate kinase and deletion of threonine deaminase further increased the production to 1.78?g/L. Overexpressions of panC and panB from Corynebacterium glutamicum enhanced the production by 29%. In fed-batch fermentations, strain DPA-9/pTrc99a-panBC(C.G) exhibited a highest D-pantothenic acid yield of 28.45?g/L. The findings in this study demonstrate the systematic metabolic engineering in Escherichia coli W3110 would be a promising strategy for industrial production of D-pantothenic acid.[3]

In other study, strategies of engineering the synthetic pathway combined with regulating methyl recycle were employed in E. coli to enhance D-pantothenic acid production. First, a self-induced promoter-mediated dynamic regulation of D-pantothenic acid degradation pathway was carried out to improve D-pantothenic acid accumulation. Then, to drive more carbon flux into D-pantothenic acid synthesis, the key nodes of the R-pantoate pathway which encoded the essential enzyme were integrated into the genome. Subsequently, the further increase in D-pantothenic acid production was achieved by promoting the regeneration of methyl donor. The strain L11T produced 86.03 g/L D-pantothenic acid with a productivity of 0.797 g/L/h, which presented the highest D-pantothenic acid titer and productivity to date. The strategies could be applied to constructing cell factories for producing other bio-based products.The degradation pathway of D-pantothenic acid, encoded by the gene coaA, was dynamically regulated by substituting the native promoter with self-inducible promoters PfliA, PflgC, PrpsL, and PrpsT. Additionally, for enhancing D-pantothenic acid synthesis, alsS (encoding acetolactate synthase from Bacillus subtilis) and panB (encoding 3-methyl-2-oxobutanoate hydroxymethyltransferase from Bacillus subtilis) were employed to redirectcarbon flux towards D-pantothenic acid synthesis. [4]

Function research

1.Potential role for cerebral D-pantothenic acid stores in local myelin homeostasis

D-pantothenic acid (Vitamin B5; pantothenate) is an essential trace nutrient that functions as the obligate precursor of coenzyme A (CoA), through which it plays key roles in myriad biological processes, including many that regulate carbohydrate, lipid, protein, and nucleic acid metabolism. In the brain, acetyl-CoA is necessary for synthesis of the complex fatty-acyl chains of myelin, and of the neurotransmitter acetylcholine. Authors recently found that cerebral D-pantothenic acid is markedly lowered, averaging ~55% of control values in cases of Huntington's disease (HD) including those who are pre-symptomatic, and that regions where D-pantothenic acid is lowered correspond to those which are more severely damaged. Here we sought to determine the previously unknown distribution of D-pantothenic acid in the normal-rat brain, and whether the diabetic rat might be useful as a model for altered cerebral D-pantothenic acid metabolism. Authors employed histological staining (Nissl) to identify brain structures; immunohistochemistry with anti-pantothenate antibodies to determine the distribution of D-pantothenic acid in caudate putamen and cerebellum; and gas-chromatography/mass-spectrometry to quantitate levels of D-pantothenic acid and other metabolites in normal- and diabetic-rat brain. Remarkably, cerebral D-pantothenic acid was almost entirely localized to myelin-containing structures in both experimental groups. Diabetes did not modify levels or disposition of cerebral D-pantothenic acid. These findings are consistent with physiological localization of D-pantothenic acid in myelinated white-matter structures, where it could serve to support myelin synthesis. Further investigation of cerebral D-pantothenic acid is warranted in neurodegenerative diseases such as HD and Alzheimer's disease, where myelin loss is a known characteristic of pathogenesis.[5]

2.D-pantothenic acid with Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of age-related neurodegeneration and dementia, and there are no available treatments with proven disease-modifying actions. It is therefore appropriate to study hitherto-unknown aspects of brain structure/function in AD to seek alternative disease-related mechanisms that might be targeted by new therapeutic interventions with disease-modifying actions. During hypothesis-generating metabolomic studies of brain, researchers identified apparent differences in levels of D-pantothenic acid between AD cases and controls. We therefore developed a method based on gas chromatography-mass spectrometry by which we quantitated D-pantothenic acid concentrations in seven brain regions from nine AD cases and nine controls. Researchers found that widespread, severe cerebral deficiency of D-pantothenic acid occurs in AD. This deficiency was worse in those regions known to undergo severe damage, including the hippocampus, entorhinal cortex, and middle temporal gyrus. D-pantothenic acid is the obligate precursor of CoA/acetyl-CoA (acetyl-coenzyme A), which plays myriad key roles in the metabolism of all organs, including the brain. In brain, acetyl-CoA is the obligate precursor of the neurotransmitter acetylcholine, and the complex fatty-acyl groups that mediate the essential insulator role of myelin, both processes being defective in AD; moreover, the large cerebral D-pantothenic acid concentrations co-localize almost entirely to white matter. D-pantothenic acid is well tolerated when administered orally to humans and other mammals. Vitamin B5 dysregulation could lieat the centre of disturbed brain energetics, including the previouslyreported polyol-pathway activation and concomitant impairmentof glycolysis in AD brain. Researchers conclude that cerebral D-pantothenic acid deficiency may well cause neurodegeneration and dementia in AD, which might be preventable or even reversible in its early stages, by treatment with suitable oral doses of D-pantothenic acid.[6]

References

1. Zou SP, Wang ZJ, Zhao K, et al. High-level production of d-pantothenic acid from glucose by fed-batch cultivation of Escherichia coli. Biotechnol Appl Biochem. 2021;68(6):1227-1235. doi:10.1002/bab.2044

2. Kelly GS. Pantothenic acid. Monograph. Altern Med Rev. 2011;16(3):263-274.

3. Zhang B, Zhang XM, Wang W, Liu ZQ, Zheng YG. Metabolic engineering of Escherichia coli for d-pantothenic acid production. Food Chem. 2019;294:267-275. doi:10.1016/j.foodchem.2019.05.044

4. Zou S, Liu J, Zhao K, et al. Metabolic engineering of Escherichia coli for enhanced production of D-pantothenic acid. Bioresour Technol. 2024;412:131352. doi:10.1016/j.biortech.2024.131352

5. Ismail N, Kureishy N, Church SJ, et al. Vitamin B5 (d-pantothenic acid) localizes in myelinated structures of the rat brain: Potential role for cerebral vitamin B5 stores in local myelin homeostasis. Biochem Biophys Res Commun. 2020;522(1):220-225. doi:10.1016/j.bbrc.2019.11.052

6. Xu J, Patassini S, Begley P, et al. Cerebral deficiency of vitamin B5 (d-pantothenic acid; pantothenate) as a potentially-reversible cause of neurodegeneration and dementia in sporadic Alzheimer's disease. Biochem Biophys Res Commun. 2020;527(3):676-681. doi:10.1016/j.bbrc.2020.05.015