Vanin1 (VNN1) in chronic diseases: Future directions for targeted therapy

Vanin1 (VNN1) is an exogenous enzyme with pantetheinase activity that mainly exerts physiological functions through enzyme catalysis products, including pantothenic acid and cysteamine. In recent years, the crosstalk between VNN1 and metabolism and oxidative stress has attracted much attention. As a result of the ability of VNN1 to affect multiple metabolic pathways and oxidative stress to exacerbate or alleviate pathological processes, it has become a key component of disease progression. This review discusses the functions of VNN1 in glucolipid metabolism, cysteamine metabolism, and glutathione metabolism to provide perspectives on VNN1-targeted therapy for chronic diseases.

Dynamically Regulating Glucose Uptake to Reduce Overflow Metabolism with a Quorum-Sensing Circuit for the Efficient Synthesis of d-Pantothenic Acid in Bacillus subtilis

In response to a high concentration of glucose, Bacillus subtilis, a microbial chassis for producing many industrial metabolites, rapidly takes up glucose using the phosphotransferase system (PTS), leading to overflow metabolism, a common phenomenon observed in many bacteria. Although overflow metabolism affects cell growth and reduces the production of many metabolites, effective strategies that reduce overflow metabolism while maintaining normal cell growth remain to be developed. Here, we used a quorum sensing (QS)-mediated circuit to tune the glucose uptake rate and thereby relieve overflow metabolism in an engineered B. subtilis for producing d-pantothenic acid (DPA). A low-efficiency non-PTS system was used for glucose uptake at the early growth stages to avoid a rapid glycolytic flux, while an efficient PTS system, which was activated by a QS circuit, was automatically activated at the late growth stages after surpassing a threshold cell density. This strategy was successfully applied as a modular metabolic engineering process for the high production of DPA. By enhancing the translation levels of key enzymes (3-methyl-2-oxobutanoate hydroxymethytransferase, pantothenate synthetase, aspartate 1-decarboxylase proenzyme, 2-dehydropantoate 2-reductase, dihydroxy-acid dehydratase, and acetolactate synthase) with engineered 5'-untranslated regions (UTRs) of mRNAs, the metabolic flux was promoted in the direction of DPA production, elevating the yield of DPA to 5.11 g/L in shake flasks. Finally, the engineered B. subtilis produced 21.52 g/L of DPA in fed-batch fermentations. Our work not only revealed a new strategy for reducing overflow metabolism by adjusting the glucose uptake rate in combination with promoting the translation of key metabolic enzymes through engineering the 5'-UTR of mRNAs but also showed its power in promoting the bioproduction of DPA in B. subtilis, exhibiting promising application prospects.

The vitamin B5/coenzyme A axis: A target for immunomodulation?

Coenzyme A (CoA) serves as a vital cofactor in numerous enzymatic reactions involved in energy production, lipid metabolism, and synthesis of essential molecules. Dysregulation of CoA-dependent metabolic pathways can contribute to chronic diseases, such as inflammatory diseases, obesity, diabetes, cancer, and cardiovascular disorders. Additionally, CoA influences immune cell activation by modulating the metabolism of these cells, thereby affecting their proliferation, differentiation, and effector functions. Targeting CoA metabolism presents a promising avenue for therapeutic intervention, as it can potentially restore metabolic balance, mitigate chronic inflammation, and enhance immune cell function. This might ultimately improve the management and outcomes for these diseases. This review will more specifically focus on the contribution of pathways regulating the availability of the CoA precursor Vitamin B5/pantothenate in vivo and modulating the development of Th17-mediated inflammation, CD8-dependent anti-tumor immunity but also tissue repair processes in chronic inflammatory or degenerative diseases.

Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells

Mutations in the Transport and Golgi Organization 2 (TANGO2) gene are associated with intellectual deficit, neurodevelopmental delay and regression. Individuals can also present with an acute metabolic crisis that includes rhabdomyolysis, cardiomyopathy, and cardiac arrhythmias, the latter of which are potentially lethal. While preventing metabolic crises has the potential to reduce mortality, no treatments currently exist for this condition. The function of TANGO2 remains unknown but is suspected to be involved in some aspect of lipid metabolism. Here, we describe a model of TANGO2-related disease in the fruit fly Drosophila melanogaster that recapitulates crucial disease traits. Pairing a new fly model with human cells, we examined the effects of vitamin B5, a coenzyme A (CoA) precursor, on alleviating the cellular and organismal defects associated with TANGO2 deficiency. We demonstrate that vitamin B5 specifically improves multiple defects associated with TANGO2 loss-of-function in Drosophila and rescues membrane trafficking defects in human cells. We also observed a partial rescue of one of the fly defects by vitamin B3, though to a lesser extent than vitamin B5. Our data suggest that a B complex supplement containing vitamin B5/pantothenate may have therapeutic benefits in individuals with TANGO2-deficiency disease. Possible mechanisms for the rescue are discussed that may include restoration of lipid homeostasis.

High-resolution crystal structure and chemical screening reveal pantothenate kinase as a new target for antifungal development

Fungal infections are the leading cause of mortality by eukaryotic pathogens, with an estimated 150 million severe life-threatening cases and 1.7 million deaths reported annually. The rapid emergence of multidrug-resistant fungal isolates highlights the urgent need for new drugs with new mechanisms of action. In fungi, pantothenate phosphorylation, catalyzed by PanK enzyme, is the first step in the utilization of pantothenic acid and coenzyme A biosynthesis. In all fungi sequenced so far, this enzyme is encoded by a single PanK gene. Here, we report the crystal structure of a fungal PanK alone as well as with high-affinity inhibitors from a single chemotype identified through a high-throughput chemical screen. Structural, biochemical, and functional analyses revealed mechanisms governing substrate and ligand binding, dimerization, and catalysis and helped identify new compounds that inhibit the growth of several Candida species. The data validate PanK as a promising target for antifungal drug development.

Novel biallelic variants expand the SLC5A6-related phenotypic spectrum

The sodium (Na+):multivitamin transporter (SMVT), encoded by SLC5A6, belongs to the sodium:solute symporter family and is required for the Na+-dependent uptake of biotin (vitamin B7), pantothenic acid (vitamin B5), the vitamin-like substance α-lipoic acid, and iodide. Compound heterozygous SLC5A6 variants have been reported in individuals with variable multisystemic disorder, including failure to thrive, developmental delay, seizures, cerebral palsy, brain atrophy, gastrointestinal problems, immunodeficiency, and/or osteopenia. We expand the phenotypic spectrum associated with biallelic SLC5A6 variants affecting function by reporting five individuals from three families with motor neuropathies. We identified the homozygous variant c.1285 A > G [p.(Ser429Gly)] in three affected siblings and a simplex patient and the maternally inherited c.280 C > T [p.(Arg94*)] variant and the paternally inherited c.485 A > G [p.(Tyr162Cys)] variant in the simplex patient of the third family. Both missense variants were predicted to affect function by in silico tools. 3D homology modeling of the human SMVT revealed 13 transmembrane helices (TMs) and Tyr162 and Ser429 to be located at the cytoplasmic facing region of TM4 and within TM11, respectively. The SLC5A6 missense variants p.(Tyr162Cys) and p.(Ser429Gly) did not affect plasma membrane localization of the ectopically expressed multivitamin transporter suggesting reduced but not abolished function, such as lower catalytic activity. Targeted therapeutic intervention yielded clinical improvement in four of the five patients. Early molecular diagnosis by exome sequencing is essential for timely replacement therapy in affected individuals.

Comparative metabolic profiling of posterior parietal cortex, amygdala, and hippocampus in conditioned fear memory

Fear conditioning and retrieval are suitable models to investigate the biological basis of various mental disorders. Hippocampus and amygdala neurons consolidate conditioned stimulus (CS)-dependent fear memory. Posterior parietal cortex is considered important for the CS-dependent conditioning and retrieval of fear memory. Metabolomic screening among functionally related brain areas provides molecular signatures and biomarkers to improve the treatment of psychopathologies. Herein, we analyzed and compared changes of metabolites in the hippocampus, amygdala, and posterior parietal cortex under the fear retrieval condition. Metabolite profiles of posterior parietal cortex and amygdala were similarly changed after fear memory retrieval. While the retrieval of fear memory perturbed various metabolic pathways, most metabolic pathways that overlapped among the three brain regions had high ranks in the enrichment analysis of posterior parietal cortex. In posterior parietal cortex, the most perturbed pathways were pantothenate and CoA biosynthesis, purine metabolism, glutathione metabolism, and NAD+ dependent signaling. Metabolites of posterior parietal cortex including 4'-phosphopantetheine, xanthine, glutathione, ADP-ribose, ADP-ribose 2'-phosphate, and cyclic ADP-ribose were significantly regulated in these metabolic pathways. These results point to the importance of metabolites of posterior parietal cortex in conditioned fear memory retrieval and may provide potential biomarker candidates for traumatic memory-related mental disorders.

Protective effect of isosteviol sodium against LPS-induced multiple organ injury by regulating of glycerophospholipid metabolism and reducing macrophage-driven inflammation

Sepsis is a severe inflammatory disorder that can lead to multiple organ injury. Isosteviol sodium (STV-Na) is a terpenoid derived from stevioside that exerts anti-inflammatory, antioxidant and antiapoptotic activities. However, the influence of STV-Na on sepsis remains unknown. Here, we assessed the potential effects of STV-Na on sepsis and multiple organ injury induced by lipopolysaccharide (LPS). We found that STV-Na increased the survival rate of mice treat with LPS, significantly improved the functions of the heart, lung, liver, and kidney, reduced the production of inflammatory cytokines and decreased macrophage infiltration. Moreover, Multiorgan metabolomics analysis demonstrated that glutathione metabolism, purine metabolism, glycerophospholipid metabolism and pantothenate and CoA biosynthesis, were significantly altered by STV-Na. This study provides novel insights into the metabolite changes of multiple organ injury in septic mice, which may help characterize the underlying mechanism and provide an improved understanding of the therapeutic effects of STV-Na on sepsis.

Turnover rate of coenzyme A in mouse brain and liver

Coenzyme A (CoA) is a fundamental cofactor involved in a number of important biochemical reactions in the cell. Altered CoA metabolism results in severe conditions such as pantothenate kinase-associated neurodegeneration (PKAN) in which a reduction of the activity of pantothenate kinase isoform 2 (PANK2) present in CoA biosynthesis in the brain consequently lowers the level of CoA in this organ. In order to develop a new drug aimed at restoring the sufficient amount of CoA in the brain of PKAN patients, we looked at its turnover. We report here the results of two experiments that enabled us to measure the half-life of pantothenic acid, free CoA (CoASH) and acetylCoA in the brains and livers of male and female C57BL/6N mice, and total CoA in the brains of male mice. We administered (intrastriatally or orally) a single dose of a [13C3-15N-18O]-labelled coenzyme A precursor (fosmetpantotenate or [13C3-15N]-pantothenic acid) to the mice and measured, by liquid chromatography-mass spectrometry, unlabelled- and labelled-coenzyme A species appearance and disappearance over time. We found that the turnover of all metabolites was faster in the liver than in the brain in both genders with no evident gender difference observed. In the oral study, the CoASH half-life was: 69 ± 5 h (male) and 82 ± 6 h (female) in the liver; 136 ± 14 h (male) and 144 ± 12 h (female) in the brain. AcetylCoA half-life was 74 ± 9 h (male) and 71 ± 7 h (female) in the liver; 117 ± 13 h (male) and 158 ± 23 (female) in the brain. These results were in accordance with the corresponding values obtained after intrastriatal infusion of labelled-fosmetpantotenate (CoASH 124 ± 13 h, acetylCoA 117 ± 11 and total CoA 144 ± 17 in male brain).

Red emission ratio fluorescent probe for the activity of vanin-1 and imaging in vivo

Pantetheinase, also known as Vanin-1, catalyzes pantetheine to decompose into the precursor of CoA - pantothenic acid and aminothiol cysteamine. Studies have shown that Vanin-1 plays an important role in many important physiological pathologies. In this paper, a new red emission ratio fluorescent probe DCM-PA (I_{640 nm}/I_{564 nm}) has been implemented to detect the activity of Vanin-1 in cells and vivo. DCM-PA has short response time (30 min), high selectivity and low sensitivity (DL =0.69 ng/mL). Also, we have applied DCM-PA for imaging in cells and mice, and the results have indicated that the probe has a non-negligible potential for monitoring the activity of Vanin-1 in situ, benefiting further to study the role of Vanin-1 in physiology and pathology. In addition, the up-regulation of this enzyme by starvation confirmed the inevitable connection between diabetes and abnormal expression of Vanin-1.

B-vitamin nutrition in the pea aphid-Buchnera symbiosis

Various insects that utilize vitamin-deficient diets derive a supplementary supply of these micronutrients from their symbiotic microorganisms. Here, we tested the inference from genome annotation that the symbiotic bacterium Buchnera aphidicola in the pea aphid Acyrthosiphon pisum provides the insect with vitamins B₂ and B₅ but no other B-vitamins. Contrary to expectation, aphid survival over five days of larval development on artificial diets individually lacking each B-vitamin not synthesized by Buchnera was not significantly reduced, despite significantly lower carcass B₁, B₃, B₆ and B₇ concentrations in the aphids on diets lacking each of these B-vitamins than on the vitamin-complete diet. Aphid survival was, however, significantly reduced on diet containing low concentrations (≤0.2 mM) or no pantothenate (B₅). Complementary transcriptome analysis revealed low abundance of the sense-transcript, but high abundance of the antisense transcript, of the Buchnera gene panC encoding the enzyme mediating the terminal reaction in pantothenate synthesis. We hypothesize that metabolic constraints or antisense transcripts may reduce Buchnera-mediated production of pantothenate, resulting in poor aphid performance on pantothenate-free diets. The discrepancy between predictions from genome data and empirical data illustrates the need for physiological study to test functional inferences made from genome annotations.

Cerebral deficiency of vitamin B5 (d-pantothenic acid; pantothenate) as a potentially-reversible cause of neurodegeneration and dementia in sporadic 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, we identified apparent differences in levels of vitamin B5 between AD cases and controls. We therefore developed a method based on gas chromatography-mass spectrometry by which we quantitated vitamin B5 concentrations in seven brain regions from nine AD cases and nine controls. We found that widespread, severe cerebral deficiency of vitamin B5 occurs in AD. This deficiency was worse in those regions known to undergo severe damage, including the hippocampus, entorhinal cortex, and middle temporal gyrus. Vitamin B5 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 vitamin B5 concentrations co-localize almost entirely to white matter. Vitamin B5 is well tolerated when administered orally to humans and other mammals. We conclude that cerebral vitamin B5 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 vitamin B5.

Functional interrogation of Plasmodium genus metabolism identifies species- and stage-specific differences in nutrient essentiality and drug targeting

Several antimalarial drugs exist, but differences between life cycle stages among malaria species pose challenges for developing more effective therapies. To understand the diversity among stages and species, we reconstructed genome-scale metabolic models (GeMMs) of metabolism for five life cycle stages and five species of Plasmodium spanning the blood, transmission, and mosquito stages. The stage-specific models of Plasmodium falciparum uncovered stage-dependent changes in central carbon metabolism and predicted potential targets that could affect several life cycle stages. The species-specific models further highlight differences between experimental animal models and the human-infecting species. Comparisons between human- and rodent-infecting species revealed differences in thiamine (vitamin B1), choline, and pantothenate (vitamin B5) metabolism. Thus, we show that genome-scale analysis of multiple stages and species of Plasmodium can prioritize potential drug targets that could be both anti-malarials and transmission blocking agents, in addition to guiding translation from non-human experimental disease models.

Malaria kills nearly one-half million people a year and over 1 billion people are at risk of becoming infected by the parasite. Plasmodial infections are difficult to treat for a myriad of reasons, but the ability of the organism to remain latent in hosts and the complex life cycles greatly contributed to the difficulty in treat malaria. Genome-scale metabolic models (GeMMs) enable hierarchical integration of disparate data types into a framework amenable to computational simulations enabling deeper mechanistic insights from high-throughput data measurements. In this study, GeMMs of multiple Plasmodium species are used to study metabolic similarities and differences across the Plasmodium genus. In silico gene-knock out simulations across species and stages uncovered functional metabolic differences between human- and rodent-infecting species as well as across the parasite’s life-cycle stages. These findings may help identify drug regimens that are more effective in targeting human-infecting species across multiple stages of the organism.

Dietary pantothenic acid depressed the gill immune and physical barrier function via NF-κB, TOR, Nrf2, p38MAPK and MLCK signaling pathways in grass carp (Ctenopharyngodon idella)

This study explored the effects of pantothenic acid (PA) on the immune and physical barrier function, and relative mRNA levels of signaling molecules in the gill of grass carp (Ctenopharyngodon idella). The results indicated that compared with optimal PA supplementation, PA deficiency (1.31 mg/kg diet) decreased gill interleukin 10, transforming growth factor β1, inhibitor of κBα (IκBα), eIF4E-binding protein 2, Claudin b and ZO-1 mRNA levels; anti-superoxide anion activity, and activities and mRNA levels of copper/zinc superoxide dismutase, manganese superoxide dismutase, glutathione peroxidase, glutathione reductase and NF-E2-related factor (P < 0.05). Additionally, PA deficiency and excess (75.08 mg/kg diet) decreased gill complement 3 and glutathione contents, lysozyme and acid phosphatase, anti-hydroxy radical, catalase and glutathione S-transferases activities, and liver-expression antimicrobial peptide 2, hepcidin, Claudin 3, Claudin c and Occludin mRNA levels (P < 0.05). Conversely, PA deficiency increased gill reactive oxygen species and protein carbonyl contents, and interferon γ2, interleukin 8, nuclear factor kappa B P65, Claudin 15a, Kelch-like ECH-associating protein 1a and Kelch-like ECH-associating protein 1b mRNA levels (P<0.05). Moreover, PA deficiency and excess increased gill malondialdehyde content, and tumor necrosis factor α, interleukin 1β, IκB kinase α, IκB kinase β, IκB kinase γ, target of rapamycin and ribosomal S6 protein kinase1 p38 mitogen-activated protein kinases and myosin light-chain kinase mRNA levels (P<0.05). In conclusion, PA deficiency decreased immune and physical barrier function, and regulated relative mRNA levels of signaling molecules in fish gill. Based on the quadratic regression analysis of gill lysozyme activity, the optimal PA levels in grass carp (253.44-745.25 g) were estimated to be 36.97 mg/kg diet.

Large-scaled metabolic profiling of human dermal fibroblasts derived from pseudoxanthoma elasticum patients and healthy controls

Mutations in the ABC transporter ABCC6 were recently identified as cause of Pseudoxanthoma elasticum (PXE), a rare genetic disorder characterized by progressive mineralization of elastic fibers. We used an untargeted metabolic approach to identify biochemical differences between human dermal fibroblasts from healthy controls and PXE patients in an attempt to find a link between ABCC6 deficiency, cellular metabolic alterations and disease pathogenesis. 358 compounds were identified by mass spectrometry covering lipids, amino acids, peptides, carbohydrates, nucleotides, vitamins and cofactors, xenobiotics and energy metabolites. We found substantial differences in glycerophospholipid composition, leucine dipeptides, and polypeptides as well as alterations in pantothenate and guanine metabolism to be significantly associated with PXE pathogenesis. These findings can be linked to extracellular matrix remodeling and increased oxidative stress, which reflect characteristic hallmarks of PXE. Our study could facilitate a better understanding of biochemical pathways involved in soft tissue mineralization.

Behavioral metabolomics analysis identifies novel neurochemical signatures in methamphetamine sensitization

Behavioral sensitization has been widely studied in animal models and is theorized to reflect neural modifications associated with human psychostimulant addiction. While the mesolimbic dopaminergic pathway is known to play a role, the neurochemical mechanisms underlying behavioral sensitization remain incompletely understood. In this study, we conducted the first metabolomics analysis to globally characterize neurochemical differences associated with behavioral sensitization. Methamphetamine (MA)-induced sensitization measures were generated by statistically modeling longitudinal activity data for eight inbred strains of mice. Subsequent to behavioral testing, nontargeted liquid and gas chromatography-mass spectrometry profiling was performed on 48 brain samples, yielding 301 metabolite levels per sample after quality control. Association testing between metabolite levels and three primary dimensions of behavioral sensitization (total distance, stereotypy and margin time) showed four robust, significant associations at a stringent metabolome-wide significance threshold (false discovery rate, FDR <0.05). Results implicated homocarnosine, a dipeptide of GABA and histidine, in total distance sensitization, GABA metabolite 4-guanidinobutanoate and pantothenate in stereotypy sensitization, and myo-inositol in margin time sensitization. Secondary analyses indicated that these associations were independent of concurrent MA levels and, with the exception of the myo-inositol association, suggest a mechanism whereby strain-based genetic variation produces specific baseline neurochemical differences that substantially influence the magnitude of MA-induced sensitization. These findings demonstrate the utility of mouse metabolomics for identifying novel biomarkers, and developing more comprehensive neurochemical models, of psychostimulant sensitization.

Conditional knockout of the Slc5a6 gene in mouse intestine impairs biotin absorption

The Slc5a6 gene expresses a plasma membrane protein involved in the transport of the water-soluble vitamin biotin; the transporter is commonly referred to as the sodium-dependent multivitamin transporter (SMVT) because it also transports pantothenic acid and lipoic acid. The relative contribution of the SMVT system toward carrier-mediated biotin uptake in the native intestine in vivo has not been established. We used a Cre/lox technology to generate an intestine-specific (conditional) SMVT knockout (KO) mouse model to address this issue. The KO mice exhibited absence of expression of SMVT in the intestine compared with sex-matched littermates as well as the expected normal SMVT expression in other tissues. About two-thirds of the KO mice died prematurely between the age of 6 and 10 wk. Growth retardation, decreased bone density, decreased bone length, and decreased biotin status were observed in the KO mice. Microscopic analysis showed histological abnormalities in the small bowel (shortened villi, dysplasia) and cecum (chronic active inflammation, dysplasia) of the KO mice. In vivo (and in vitro) transport studies showed complete inhibition in carrier-mediated biotin uptake in the intestine of the KO mice compared with their control littermates. These studies provide the first in vivo confirmation in native intestine that SMVT is solely responsible for intestinal biotin uptake. These studies also provide evidence for a casual association between SMVT function and normal intestinal health.

The missing link in coenzyme A biosynthesis: PanM (formerly YhhK), a yeast GCN5 acetyltransferase homologue triggers aspartate decarboxylase (PanD) maturation in Salmonella enterica

Coenzyme A (CoA) is an essential cofactor for all forms of life. The biochemistry underpinning the assembly of CoA in Escherichia coli and other enterobacteria is well understood, except for the events leading to maturation of the L-aspartate-α-decarboxylase (PanD) enzyme that converts pantothenate to β-alanine. PanD is synthesized as pro-PanD, which undergoes an auto-proteolytic cleavage at residue Ser25 to yield the catalytic pyruvoyl moiety of the enzyme. Since 1990, it has been known that E. coli yhhK strains are pantothenate auxotrophs, but the role of YhhK in pantothenate biosynthesis remained an enigma. Here we show that Salmonella enterica yhhK strains are also pantothenate auxotrophs. In vivo and in vitro evidence shows that YhhK interacts directly with PanD, and that such interactions accelerate pro-PanD maturation. We also show that S. enterica yhhK strains accumulate pro-PanD, and that not all pro-PanD proteins require YhhK for maturation. For example, the Corynebacterium glutamicum panD(+) gene corrected the pantothenate auxotrophy of a S. enterica yhhK strain, supporting in vitro evidence obtained by others that some pro-PanD proteins autocleave at faster rates. We propose the name PanM for YhhK to reflect its role as a trigger of pro-PanD maturation by stabilizing pro-PanD in an autocleavage-prone conformation.

Priming with a recombinant pantothenate auxotroph of Mycobacterium bovis BCG and boosting with MVA elicits HIV-1 Gag specific CD8+ T cells

A safe and effective HIV vaccine is required to significantly reduce the number of people becoming infected with HIV each year. In this study wild type Mycobacterium bovis BCG Pasteur and an attenuated pantothenate auxotroph strain (BCGΔpanCD) that is safe in SCID mice, have been compared as vaccine vectors for HIV-1 subtype C Gag. Genetically stable vaccines BCG[pHS400] (BCG-Gag) and BCGΔpanCD[pHS400] (BCGpan-Gag) were generated using the Pasteur strain of BCG, and a panothenate auxotroph of Pasteur respectively. Stability was achieved by the use of a codon optimised gag gene and deletion of the hsp60-lysA promoter-gene cassette from the episomal vector pCB119. In this vector expression of gag is driven by the mtrA promoter and the Gag protein is fused to the Mycobacterium tuberculosis 19 kDa signal sequence. Both BCG-Gag and BCGpan-Gag primed the immune system of BALB/c mice for a boost with a recombinant modified vaccinia virus Ankara expressing Gag (MVA-Gag). After the boost high frequencies of predominantly Gag-specific CD8(+) T cells were detected when BCGpan-Gag was the prime in contrast to induction of predominantly Gag-specific CD4(+) T cells when priming with BCG-Gag. The differing Gag-specific T-cell phenotype elicited by the prime-boost regimens may be related to the reduced inflammation observed with the pantothenate auxotroph strain compared to the parent strain. These features make BCGpan-Gag a more desirable HIV vaccine candidate than BCG-Gag. Although no Gag-specific cells could be detected after vaccination of BALB/c mice with either recombinant BCG vaccine alone, BCGpan-Gag protected mice against a surrogate vaccinia virus challenge.

The changes in pectin metabolism in flax infected with Fusarium

Fusarium culmorum and Fusarium oxysporum are the most common fungal pathogens of flax (Linum usitatissimum L.), thus leading to the greatest losses in crop yield. A subtractive cDNA library was constructed from flax seedlings exposed for two days to F. oxysporum. This revealed a set of genes that are potentially involved in the flax defense responses. Two of those genes directly participate in cell wall sugar polymer metabolism: UDP-D-glucuronate 4-epimerase (GAE; EC 5.1.3.6) and formate dehydrogenase (FDH; EC 1.2.1.2). GAE delivers the main substrate for pectin biosynthesis, and decreases were detected in its mRNA level after Fusarium infection. FDH participates in the metabolism of formic acid, and the expression level of its gene increased after Fusarium infection. However, metabolite profiling analysis disclosed that the pectin content in the infected plants remained unchanged, but that there were reductions in both the levels of the soluble sugars that serve as pectin precursors, and in the level of formic acid. Since formic acid is the product of pectin demethylesterification, the level of mRNAs coding for pectin methylesterase (EC 3.1.1.11) in the infected flax was measured, revealing a decrease in its expression upon plant infection. Transgenic flax plants overexpressing fungal polygalacturonase (EC 3.2.1.15) and rhamnogalacturonase (EC 3.2.1.-) showed a decrease in the pectin content and an elevated level of formic acid, but the level of expression of the FDH gene remained unchanged. It is suspected that the expression of the formate dehydrogenase gene is directly controlled by the pathogen in the early stage of infection, and additionally by pectin degradation in the later stages.

Towards engineering increased pantothenate (vitamin B(5)) levels in plants

Pantothenate (vitamin B(5)) is the precursor of the 4'-phosphopantetheine moiety of coenzyme A and acyl-carrier protein. It is made by plants and microorganisms de novo, but is a dietary requirement for animals. The pantothenate biosynthetic pathway is well-established in bacteria, comprising four enzymic reactions catalysed by ketopantoate hydroxymethyltransferase (KPHMT), L: -aspartate-alpha-decarboxylase (ADC), pantothenate synthetase (PS) and ketopantoate reductase (KPR) encoded by panB, panD, panC and panE genes, respectively. In higher plants, the genes encoding the first (KPHMT) and last (PS) enzymes have been identified and characterised in several plant species. Commercially, pantothenate is chemically synthesised and used in vitamin supplements, feed additives and cosmetics. Biotransformation is an attractive alternative production system that would circumvent the expensive procedures of separating racemic intermediates. We explored the possibility of manipulating pantothenate biosynthesis in plants. Transgenic oilseed rape (Brassica napus) lines were generated in which the E. coli KPHMT and PS genes were expressed under a strong constitutive CaMV35SS promoter. No significant change of pantothenate levels in PS transgenic lines was observed. In contrast plants expressing KPHMT had elevated pantothenate levels in leaves, flowers siliques and seed in the range of 1.5-2.5 fold increase compared to the wild type plant. Seeds contained the highest vitamin content, indicating that they might be the ideal target for production purposes.

[Metalloproteinases. Structure and function]

Matrix metalloproteinases (MMPs) belong to a large family of multidomain zinc endopeptidases. They are one of the most important proteolitic enzymes which digest components of the extracellular matrix and abundant macromolecules on cell surface and take part in many physiological processes, such as apoptosis or angiogenesis. MMPs are also engaged in the pathogenesis of many diseases such as arthritis and cancer. The development of effective inhibitors and discovery of their mechanisms of action can have significant influence on therapeutic strategy.

How pantothenol intervenes in Coenzyme-A biosynthesis of Mycobacterium tuberculosis

Coenzyme A is an indispensable cofactor for all organisms and holds a central position in a number of pathways. Prokaryotic enzymes involved in the synthesis of CoA are quite different from their mammalian counterparts; hence, they are good targets for the development of antimicrobials to treat many diseases. There are antimicrobials that act by inhibiting CoA biosynthesis. It has been suggested that pantothenol exhibits antibacterial activity by competitively inhibiting pantothenate kinase, a key regulatory enzyme for CoA synthesis. Contrary to these suggestions, in this paper, we demonstrate that pantothenol acts as a substrate for Mycobacterium tuberculosis and Escherichia coli pantothenate kinases. The product, 4'-phosphopantothenol, thus formed inhibits competitively the utilization of 4'-phosphopantothenate by CoaBC. Thus, it is the failure of CoaBC to utilize 4'-phosphopantothenol as a substrate that accounts for the bactericidal activity of pantothenol.

Feedback inhibition of pantothenate kinase regulates pantothenol uptake by the malaria parasite

To survive, the human malaria parasite Plasmodium falciparum must acquire pantothenate (vitamin B5) from the external medium. Pantothenol (provitamin B5) inhibits parasite growth by competing with pantothenate for pantothenate kinase, the first enzyme in the coenzyme A biosynthesis pathway. In this study we investigated pantothenol uptake by P. falciparum and in doing so gained insights into the regulation of the parasite's coenzyme A biosynthesis pathway. Pantothenol was shown to enter P. falciparum-infected erythrocytes via two routes, the furosemide-inhibited "new permeation pathways" induced by the parasite in the infected erythrocyte membrane (the sole access route for pantothenate) and a second, furosemide-insensitive pathway. Having entered the erythrocyte, pantothenol is taken up by the intracellular parasite via a mechanism showing functional characteristics distinct from those of the parasite's pantothenate uptake mechanism. On reaching the parasite cytosol, pantothenol is phosphorylated and thereby trapped by pantothenate kinase, shown here to be under feedback inhibition control by coenzyme A. Furosemide reduced this inherent feedback inhibition by competing with coenzyme A for binding to pantothenate kinase, thereby increasing pantothenol uptake.

REVIEW: Vitamin transport and homeostasis in mammalian brain: focus on Vitamins B and E

With the application of genetic and molecular biology techniques, there has been substantial progress in understanding how vitamins are transferred across the mammalian blood-brain barrier and choroid plexus into brain and CSF and how vitamin homeostasis in brain is achieved. In most cases (with the exception of the sodium-dependent multivitamin transporter for biotin, pantothenic acid, and lipoic acid), the vitamins are transported by separate carriers through the blood-brain barrier or choroid plexus. Then the vitamins are accumulated by brain cells by separate, specialized systems. This review focuses on six vitamins (B(1), B(3), B(6), pantothenic acid, biotin, and E) and the newer genetic information including relevant 'knockdown' or 'knockout' models in mice and humans. The overall objective is to integrate this newer information with previous physiological and biochemical observations to achieve a better understanding of vitamin transport and homeostasis in brain. This is especially important in view of the newly described non-cofactor vitamin roles in brain (e.g. of B(1), B(3), B(6), and E) and the potential roles of vitamins in the therapy of brain disorders.

Differential gene expression in mouse liver associated with the hepatoprotective effect of clofibrate

Pretreatment of mice with the peroxisome proliferator clofibrate (CFB) protects against acetaminophen (APAP)-induced hepatotoxicity. Previous studies have shown that activation of the nuclear peroxisome proliferator activated receptor-alpha (PPARalpha) is required for this effect. The present study utilizes gene expression profile analysis to identify potential pathways contributing to PPARalpha-mediated hepatoprotection. Gene expression profiles were compared between wild type and PPARalpha-null mice pretreated with vehicle or CFB (500 mg/kg, i.p., daily for 10 days) and then challenged with APAP (400 mg/kg, p.o.). Total hepatic RNA was isolated 4 h after APAP treatment and hybridized to Affymetrix Mouse Genome MGU74 v2.0 GeneChips. Gene expression analysis was performed utilizing GeneSpring software. Our analysis identified 53 genes of interest including vanin-1, cell cycle regulators, lipid-metabolizing enzymes, and aldehyde dehydrogenase 2, an acetaminophen binding protein. Vanin-1 could be important for CFB-mediated hepatoprotection because this protein is involved in the synthesis of cysteamine and cystamine. These are potent antioxidants capable of ameliorating APAP toxicity in rodents and humans. HPLC-ESI/MS/MS analysis of liver extracts indicates that enhanced vanin-1 gene expression results in elevated cystamine levels, which could be mechanistically associated with CFB-mediated hepatoprotection.

Structure of the type III pantothenate kinase from Bacillus anthracis at 2.0 A resolution: implications for coenzyme A-dependent redox biology

Coenzyme A (CoASH) is the major low-molecular weight thiol in Staphylococcus aureus and a number of other bacteria; the crystal structure of the S. aureus coenzyme A-disulfide reductase (CoADR), which maintains the reduced intracellular state of CoASH, has recently been reported [Mallett, T.C., Wallen, J.R., Karplus, P.A., Sakai, H., Tsukihara, T., and Claiborne, A. (2006) Biochemistry 45, 11278-89]. In this report we demonstrate that CoASH is the major thiol in Bacillus anthracis; a bioinformatics analysis indicates that three of the four proteins responsible for the conversion of pantothenate (Pan) to CoASH in Escherichia coli are conserved in B. anthracis. In contrast, a novel type III pantothenate kinase (PanK) catalyzes the first committed step in the biosynthetic pathway in B. anthracis; unlike the E. coli type I PanK, this enzyme is not subject to feedback inhibition by CoASH. The crystal structure of B. anthracis PanK (BaPanK), solved using multiwavelength anomalous dispersion data and refined at a resolution of 2.0 A, demonstrates that BaPanK is a new member of the Acetate and Sugar Kinase/Hsc70/Actin (ASKHA) superfamily. The Pan and ATP substrates have been modeled into the active-site cleft; in addition to providing a clear rationale for the absence of CoASH inhibition, analysis of the Pan-binding pocket has led to the development of two new structure-based motifs (the PAN and INTERFACE motifs). Our analyses also suggest that the type III PanK in the spore-forming B. anthracis plays an essential role in the novel thiol/disulfide redox biology of this category A biodefense pathogen.

Effects of high-level dietary B-vitamins on performance, body composition and tissue vitamin contents of growing/finishing pigs

Forty-eight growing pigs were randomly assigned to five dietary groups and penned individually. They received a diet based on barley, wheat, corn and soya bean meal according to requirement. The experimental groups were supplemented with 400% or 800% of vitamins B(2), B(6) and pantothenic acid, or 400% or 800% of biotin, while all other vitamins were administered according to requirement. Growth performance, carcass characteristics, aspartate aminotransferase (AST), and content of vitamins in blood, liver and muscles were recorded. Growth performance showed no influence of supplementation, while backfat thickness in the group with 800% B(2)/B(6)/pantothenic acid was significantly higher. Content of B(2) in blood, liver and muscle was similar in all groups. Content of B(6) in blood and liver showed significant differences according to supplementation. The content of vitamin B(6) in muscle in the experimental groups was significantly higher than that in the control group. The content of pantothenic acid in blood and muscle in the experimental groups was significantly higher, while in liver all groups were significantly influenced by the supplementation level. Biotin content in liver showed no influence, but the content in plasma was significantly higher in the experimental groups and the content in muscle was significantly higher according to supplementation. The activity of AST showed no significant influence of the dietary vitamin level, but it was obviously decreased in the groups supplemented with biotin. The findings indicate that the dietary supplementation of vitamin B(2), B(6), pantothenic acid and biotin could not improve performance, but the contents in blood, liver and muscle.

Dietary B vitamin needs of strains of pigs with high and moderate lean growth12

Ten sets of 5 littermate pigs from each of 2 genetic strains were utilized to determine the impact of the dietary concentration of 5 B vitamins (riboflavin, niacin, pantothenic acid, cobalamin, and folacin) on growth from 9 to 28 kg of BW in pigs with high or moderate capacity for lean growth. All pigs (penned individually) were reared via a segregated, early weaning scheme, so that the lean growth potential of each strain could be expressed. The basal diet provided the 5 test vitamins at concentrations of total and estimated bioavailability equivalent to a minimum of 100 and 70%, respectively, of their estimated requirements (NRC, 1998) for 5- to 10-kg pigs. At a BW of 9 +/- 0.9 kg, pigs within each litter were allotted to the basal diet supplemented with sources of the 5 test vitamins equivalent to an additional 0, 100, 200, 300, or 400% (bioavailable) of the NRC requirements. Pigs from the high lean strain consumed less feed (P < 0.05) and gained BW faster (P < 0.02) and more efficiently (P < 0.01) than pigs of the moderate lean strain. In both lean strains, the rate and efficiency of growth were improved (P < 0.01) as dietary B vitamin concentrations were increased. However, the dietary B vitamin concentrations needed to optimize G:F were greater (P < 0.03) in the high (>470% of NRC, 1998) vs. moderate (270%) lean strain. Based on these data, the dietary needs for 1 or more of the 5 B vitamins are greater than current NRC (1998) estimates, particularly in pigs expressing a high rate of lean tissue growth. The greater need for these vitamins is not associated with greater dietary energy intake or body energy accretion rate but is potentially due to shifts in the predominant metabolic pathways.

Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism

The B vitamins are water-soluble vitamins required as coenzymes for enzymes essential for cell function. This review focuses on their essential role in maintaining mitochondrial function and on how mitochondria are compromised by a deficiency of any B vitamin. Thiamin (B1) is essential for the oxidative decarboxylation of the multienzyme branched-chain ketoacid dehydrogenase complexes of the citric acid cycle. Riboflavin (B2) is required for the flavoenzymes of the respiratory chain, while NADH is synthesized from niacin (B3) and is required to supply protons for oxidative phosphorylation. Pantothenic acid (B5) is required for coenzyme A formation and is also essential for alpha-ketoglutarate and pyruvate dehydrogenase complexes as well as fatty acid oxidation. Biotin (B7) is the coenzyme of decarboxylases required for gluconeogenesis and fatty acid oxidation. Pyridoxal (B6), folate and cobalamin (B12) properties are reviewed elsewhere in this issue. The experimental animal and clinical evidence that vitamin B therapy alleviates B deficiency symptoms and prevents mitochondrial toxicity is also reviewed. The effectiveness of B vitamins as antioxidants preventing oxidative stress toxicity is also reviewed.

Expression of bacterial L-aspartate-alpha-decarboxylase in tobacco increases beta-alanine and pantothenate levels and improves thermotolerance

L- Aspartate-alpha-decarboxylase catalyzes the decarboxylation of L -aspartate to generate Beta-alanine and carbon dioxide. This is an unusual pyruvoyl-dependent enzyme unique to prokaryotes that undergoes limited self-processing. The Escherichia coli pan D gene encoding L- aspartate-alpha-decarboxylase was expressed under a constitutive promoter in transgenic tobacco. Transgene expression was verified by assays based on RNA blots, immunoblots and enzyme activity in vitro. The pan D lines had increased levels of leaf Beta-alanine (1.2- to 4-fold), pantothenate (3.2- to 4.1-fold) and total free amino acids (up to 3.7-fold) compared to wild-type and vector controls. Growth of homozygous lines expressing E. coli L- aspartate-alpha-decarboxylase was less affected than that of the control lines when the plants were stressed for 1 week at 35 degrees C. When transferred from 35 to 30 degrees C for 3 weeks, the Pan D transgenic lines recovered significantly (P Collapse

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MESH Headings

• Acclimatization/genetics
• Acclimatization/physiology
• Biomass
• Escherichia coli/enzymology
• Escherichia coli/genetics
• Gene Expression
• Genes, Bacterial/genetics
• Germination/physiology
• Glutamate Decarboxylase/genetics
• Glutamate Decarboxylase/metabolism
• Pantothenic Acid/metabolism
• Phenotype
• Plant Leaves/metabolism
• Plants, Genetically Modified/genetics
• RNA, Messenger/genetics
• RNA, Messenger/metabolism
• Seeds/physiology
• Temperature
• Nicotiana/genetics
• Nicotiana/growth & development
• Nicotiana/metabolism
• Nicotiana/physiology
• beta-Alanine/metabolism

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Grants Collapse

Affiliation(s)

Walid M Fouad Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville, FL 32611-0690, USA
Bala Rathinasabapathi

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A class of pantothenic acid analogs inhibits Plasmodium falciparum pantothenate kinase and represses the proliferation of malaria parasites

The growth and proliferation of the human malaria parasite Plasmodium falciparum are dependent on the parasite's ability to obtain essential nutrients. One nutrient for which the parasite has an absolute requirement is the water-soluble vitamin pantothenic acid (vitamin B5). In this study, a series of pantothenic acid analogs which retain the 2,4-dihydroxy-3,3-dimethylbutyramide core of pantothenic acid but deviate in structure from one another and from pantothenic acid in the nature of the substituent attached to the amide nitrogen were synthesized using an efficient single-step synthetic route. Eight of 10 analogs tested inhibited the proliferation of intraerythrocytic P. falciparum parasites in vitro, doing so with 50% inhibitory concentrations between 15 and 200 microM. The compounds were generally selective, inhibiting the proliferation of a human cell line (the Jurkat cell line) only at concentrations severalfold higher than those required for inhibition of parasite growth. It was demonstrated that compounds in this series inhibited the phosphorylation of pantothenic acid by pantothenate kinase, the first step in the parasite's biosynthesis of the essential enzyme cofactor coenzyme A, doing so competitively, with K(i) values in the nanomolar range.

Exogenous supply of pantoyl lactone to excised leaves increases their pantothenate levels

BACKGROUND AND AIMS

All plants synthesize pantothenate but its synthesis and regulation are not well understood. The aim of this work is to study the effect of exogenous supply of precursor compounds on pantothenate levels in leaves.

METHODS

Precursor compounds were supplied in solution to excised leaves and the pantothenate content was measured using a microbial method.

KEY RESULTS

Pantothenate levels in excised leaves of Limonium latifolium, tomato (Lycopersicon esculentum), bean (Phaseolus vulgaris) and grapefruit (Citrus x paradisi) were examined following an exogenous supply of the precursor compounds pantoyl lactone or beta-alanine. Significantly higher levels of extractable pantothenate were found when pantoyl lactone was supplied, but not when beta-alanine was supplied despite a measurable uptake of beta-alanine into the leaf.

CONCLUSIONS

The results suggested that the pantoate supply may be rate-limiting or regulating pantothenate synthesis in leaves.

Coenzyme A: back in action

Coenzyme A (CoA) is a ubiquitous essential cofactor that plays a central role in the metabolism of carboxylic acids, including short- and long-chain fatty acids. In the last few years, all of the genes encoding the CoA biosynthetic enzymes have been identified and the structures of several proteins in the pathway have been determined. CoA is assembled in five steps from pantothenic acid and pathway intermediates are common to both prokaryotes and eukaryotes. In spite of the identical biochemistry, remarkable sequence differences among some of the prokaryotic and eukaryotic enzymes have been revealed by comparative genomics. Renewed interest in CoA has arisen from the realization that the biosynthetic pathway is a target for antibacterial drug discovery and from the unexpected association of a human neurodegenerative disorder with mutations in pantothenate kinase. The purpose of this review is to integrate previous knowledge with the most recent findings in the genetics, enzymology and regulation of CoA biosynthesis in bacteria, plants and mammals.

Characterization of a new pantothenate kinase isoform from Helicobacter pylori

Pantothenate kinase (PanK) catalyzes the first step in the biosynthesis of the essential and ubiquitous cofactor coenzyme A (CoA) in all organisms. Two well characterized isoforms of the enzyme are known: a prokaryotic PanK that predominates in eubacteria and a eukaryotic isoform that has primarily been characterized from mammalian and plant sources. Curiously, the genomes of certain pathogenic bacteria, including Helicobacter pylori and Pseudomonas aeruginosa, do not contain a PanK similar to either isoform, although these organisms possess all the other biosynthetic machinery required for CoA production. In this study we cloned, overexpressed and characterized an enzyme from Bacillus subtilis and its homologue from H. pylori and show that they catalyze the ATP-dependent phosphorylation of pantothenate. These enzymes do not share sequence homology with any known PanK, and unlike the bacterial and eukaryotic PanK isoforms their activity is not regulated by either CoA or acetyl-CoA. They also do not accept the pantothenic acid antimetabolite N-pentylpantothenamide as a substrate or are inhibited by it. Taken together, these results point to the identification of a third distinct isoform of PanK that accounts for the only known activity of the enzyme in pathogens such as H. pylori and P. aeruginosa.

Long-term protection against tuberculosis following vaccination with a severely attenuated double lysine and pantothenate auxotroph of Mycobacterium tuberculosis

We report the safety and immunogenicity of a double lysine and pantothenate auxotroph of Mycobacterium tuberculosis in mice. The DeltalysA DeltapanCD mutant is completely attenuated in immunocompromised SCID and gamma interferon knockout mice yet induces short-term and long-term protection in immunocompetent and CD4-deficient mice following single-dose subcutaneous vaccination.

Provitamin B5 (pantothenol) inhibits growth of the intraerythrocytic malaria parasite

Pantothenic acid, a precursor of the crucial enzyme cofactor coenzyme A, is one of a relatively few nutrients for which the intraerythrocytic parasite has an absolute and acute requirement from the external medium. In some organisms the provitamin pantothenol can serve as a source of pantothenic acid; however, this was not the case for the human malaria parasite Plasmodium falciparum. Instead, pantothenol inhibited the in vitro growth of P. falciparum via a mechanism that involves competition with pantothenate and which can be attributed to inhibition of the parasite's pantothenate kinase. Oral administration of pantothenol to mice infected with the murine parasite Plasmodium vinckei vinckei resulted in a significant inhibition of parasite proliferation. This study highlights the potential of the coenzyme A biosynthesis pathway in general, and pantothenate kinase in particular, as an antimalarial drug target.

Mechanistic studies on phosphopantothenoylcysteine decarboxylase: trapping of an enethiolate intermediate with a mechanism-based inactivating agent

Phosphopantothenoylcysteine decarboxylase (PPC-DC) catalyzes the decarboxylation of the cysteine moiety of 4'-phosphopantothenoylcysteine (PPC) to form 4'-phosphopantetheine (PPantSH); this reaction forms part of the biosynthesis of coenzyme A. The enzyme is a member of the larger family of cysteine decarboxylases including the lantibiotic-biosynthesizing enzymes EpiD and MrsD, all of which use a tightly bound flavin cofactor to oxidize the thiol moiety of the substrate to a thioaldehyde. The thioaldehyde serves to delocalize the charge that develops in the subsequent decarboxylation reaction. In the case of PPC-DC enzymes the resulting enethiol is reduced to a thiol giving net decarboxylation of cysteine, while in EpiD and MrsD it is released as the final product of the reaction. In this paper, we describe the characterization of the novel cyclopropyl-substituted product analogue 4'-phospho-N-(1-mercaptomethyl-cyclopropyl)-pantothenamide (PPanDeltaSH) as a mechanism-based inhibitor of the human PPC-DC enzyme. This inhibitor alkylates the enzyme on Cys(173), resulting in the trapping of a covalently bound enethiolate intermediate. When Cys(173) is exchanged for the weaker acid serine by site-directed mutagenesis the enethiolate reaction intermediate also accumulates. This suggests that Cys(173) serves as an active site acid in the protonation of the enethiolate intermediate in PPC-DC enzymes. We propose that this protonation step is the key mechanistic difference between the oxidative decarboxylases EpiD and MrsD (which have either serine or threonine at the corresponding position in their active sites) and PPC-DC enzymes, which also reduce the intermediate in an overall simple decarboxylation reaction.

Cell division defects of Schizosaccharomyces pombe liz1- mutants are caused by defects in pantothenate uptake

The liz1+ gene of the fission yeast Schizosaccharomyces pombe was previously identified by complementation of a mutation that causes abnormal mitosis when ribonucleotide reductase is inhibited. Liz1 has similarity to transport proteins from Saccharomyces cerevisiae, but the potential substrate and its connection to the cell division cycle remain elusive. We report here that liz1+ encodes a plasma membrane-localized active transport protein for the vitamin pantothenate, the precursor of coenzyme A (CoA). Liz1 is required for pantothenate uptake at low extracellular concentrations. A lack of pantothenate uptake results in three phenotypes: (i) slow growth, (ii) delayed septation, and (iii) aberrant mitosis in the presence of hydroxyurea (HU). All three phenotypes are suppressed by high extracellular concentrations of pantothenate, where pantothenate uptake occurs by passive diffusion. liz1Delta mutants are viable because they can synthesize pantothenate from uracil as an endogenous source. The use of uracil for both pantothenate biosynthesis and deoxyribonucleotide generation provides an explanation for the aberrant mitosis in the presence of HU. HU blocks ribonucleotide reductase, and we propose that the accumulation of ribonucleotides reduces uracil biosynthesis by feedback inhibition of aspartate transcarbamoylase. Thus, the addition of HU to liz1Delta mutants results in a shortage of pantothenate. Because liz1Delta mutants show striking similarities to mutants with defects in fatty acid biosynthesis, we propose that the shortage of pantothenate compromises fatty acid synthesis, resulting in slow growth and mitotic defects.

[Establishment of high-yield suspension cell line of Curcuma zedoaria (Berg.) Rosc and study on the volatile oil synthesis-controlling with precursors]

The condition for high-yield suspension cell line and the precursors of volatile oil synthesis of Curcuma zedoaria (Berg.) Rosc were studied. The results showed that the light yellow particle callus was suitable for establishment of the high-yield suspension cell line. The optimum conditions for cell growth were MS medium added 15-30 g/L glucose and 15-30 g/L sucrose (1:1) as carbon source, the total concentration of 80 mmol/L nitrogen source combined NH4+ with NO3- (1:3), hormones of 3.0-5.0 mg/L 6-BA, 1.0 mg/L 2,4-D and dark culture after 10-15 days light culture. The 229 g/L cell (FW) and 2.11% content of volatile oil were obtained in vitro. The addition of precursors of calcium pantothenate, ammonium acetate and potassium acetate during the middle period of the cell suspension culture enhanced the volatile oil content respectively, and ammonium acetate was most effective among them. The highest yield of volatile oil obtained was 3.11% and 8.27 g/L respectively , which was 1.25 and 1.2 times of the control group.

Acyl carrier protein is a cellular target for the antibacterial action of the pantothenamide class of pantothenate antimetabolites

Pantothenate is the precursor of the essential cofactor coenzyme A (CoA). Pantothenate kinase (CoaA) catalyzes the first and regulatory step in the CoA biosynthetic pathway. The pantothenate analogs N-pentylpantothenamide and N-heptylpantothenamide possess antibiotic activity against Escherichia coli. Both compounds are substrates for E. coli CoaA and competitively inhibit the phosphorylation of pantothenate. The phosphorylated pantothenamides are further converted to CoA analogs, which were previously predicted to act as inhibitors of CoA-dependent enzymes. Here we show that the mechanism for the toxicity of the pantothenamides is due to the inhibition of fatty acid biosynthesis through the formation and accumulation of the inactive acyl carrier protein (ACP), which was easily observed as a faster migrating protein using conformationally sensitive gel electrophoresis. E. coli treated with the pantothenamides lost the ability to incorporate [1-(14)C]acetate to its membrane lipids, indicative of the inhibition of fatty acid synthesis. Cellular CoA was maintained at the level sufficient for bacterial protein synthesis. Electrospray ionization time-of-flight mass spectrometry confirmed that the inactive ACP was the product of the transfer of the inactive phosphopantothenamide moiety of the CoA analog to apo-ACP, forming the ACP analog that lacks the sulfhydryl group for the attachment of acyl chains for fatty acid synthesis. Inactive ACP accumulated in pantothenamide-treated cells because of the active hydrolysis of regular ACP and the slow turnover of the inactive prosthetic group. Thus, the pantothenamides are pro-antibiotics that inhibit fatty acid synthesis and bacterial growth because of the covalent modification of ACP.

Delaying the mitochondrial decay of aging

Mitochondrial dysfunction may be a principal underlying event in aging, including the degenerative diseases of aging such as brain degeneration. Mitochondria provide energy for basic metabolic processes, and their decay with age impairs cellular metabolism and leads to cellular decline. Progress over the last decade in delaying the mitochondrial decay of aging is reviewed.

Active site residues in Mycobacterium tuberculosis pantothenate synthetase required in the formation and stabilization of the adenylate intermediate

Pantothenate synthetase (EC 6.3.2.1) catalyzes the formation of pantothenate from ATP, D-pantoate, and beta-alanine in bacteria, yeast, and plants. The three-dimensional structural determination of pantothenate synthetase from Mycobacterium tuberculosis has indicated specific roles for His44, His47, Asn69, Gln72, Lys160, and Gln164 residues in the binding of substrates and the pantoyl adenylate intermediate. To evaluate the functional roles of these strictly conserved residues, we constructed six Ala mutants and determined their catalytic properties. The substitution of alanine for H44, H47, N69, Q72, and K160 residues in M. tuberculosis pantothenate synthetase caused a greater than 1000-fold reduction in enzyme activity, while the Q164A mutant exhibited 50-fold less activity. The rate of the isolated adenylation reaction in single turnover studies was also reduced 40-1000-fold by the replacement of one of these six amino acids with alanine, suggesting that these residues are essential for the formation of the pantoyl adenylate intermediate. The rate of pantothenate formation from the adenylate and beta-alanine in the second half reaction could not be measured for the H44A, H47A, N69A, Q72A, and K160A mutants and was reduced 40-fold in the Q164A mutants. The activity of the K160C mutant enzyme was markedly enhanced by the alkylation of cysteine with bromoethylamine, further supporting the critical role of the K160 residue in pantoyl adenylate formation. Isothermal titration microcalorimetry analysis demonstrated that the substitution of either H47 or K160 for Ala resulted in a decreased affinity of the enzyme for ATP. These results indicate that the highly conserved His44, His47, Asn69, Gln72, Lys160 and residues are essential for the formation and stabilization of pantoyl adenylate intermediate in the pantothenate synthetase reaction.

The Structure of the Pantothenate Kinase·ADP·Pantothenate Ternary Complex Reveals the Relationship between the Binding Sites for Substrate, Allosteric Regulator, and Antimetabolites

Pantothenate kinase catalyzes the first step in the biosynthesis of coenzyme A, the major acyl group carrier in biology. In bacteria, regulation of pantothenate kinase activity is a major factor in controlling intracellular coenzyme A levels, and pantothenate analogs are growth-inhibiting antimetabolites. We have extended the structural information on Escherichia coli pantothenate kinase by determining the structure of the enzyme.ADP. pantothenate ternary complex. Pantothenate binding induces a significant conformational change in amino acids 243-263, which form a "lid" that folds over the open pantothenate binding groove. The positioning of the substrates suggests the reaction proceeds by a concerted mechanism that involves a dissociative transition state, although the negative charge neutralization of the gamma-phosphate by Arg-243, Lys-101, and Mg(2+) coupled with hydrogen bonding of the C1 of pantothenate to Asp-127 suggests different interpretations of the phosphoryl transfer mechanism of pantothenate kinase. N-alkylpantothenamides are substrates for pantothenate kinase. Modeling these antimetabolites into the pantothenate active site predicts that they bind in the same orientation as pantothenate with their alkyl chains interacting with the hydrophobic dome over the pantothenate pocket, which is also accessed by the beta-mercaptoethylamine moiety of the allosteric regulator, coenzyme A. These structural/biochemical studies illustrate the intimate relationship between the substrate, allosteric regulator, and antimetabolite binding sites on pantothenate kinase and provide a framework for studies of its catalysis and feedback regulation.

[Coenzyme A biosynthesis as universal mechanism of conjugation of exogenous and multiple pantothenic acid functions]

Development of Academician R. V. Chagovets' ideas of the regulatory role of vitamins and their derivatives in thiol-containing compound metabolism and antioxidant system formation as well as in studying non-coenzymatic functions of B-vitamins and vitamin-binding proteins had a considerable effect on the almost 40-year studies on pantothenic acid metabolism and biochemical functions by scholars at the vitaminologic school in Grodno. The concept concerning the intracellular structure of the pantothenate coenzyme form, CoA, pool (content and ratio of CoA-SH, acetyl-CoA, short-chain and long-chain acyls-CoA, coenzyme disulfide forms and CoA-S-S-proteins) was substantiated as an important metabolic regulatory factor (including glutathione system redox potential), with changes being a principal mechanism of pantothenate derivative vitamin and pharmacotherapeutic activity implementation. The effect of the latter is mediated through the systems of CoA biosynthesis and phosphopantetheine proteins, changed CoA-S-S-protein levels, which in turn maintain the intracellular level of CoA-SH as well as cytosolic and mitochondrial transport of its vitamin-containing precursors. A universal CoA biosynthetic function was revealed in prevention of lipid peroxidation initiation and oxidative stress development.

Protection elicited by a double leucine and pantothenate auxotroph of Mycobacterium tuberculosis in guinea pigs

We developed a live, fully attenuated Mycobacterium tuberculosis vaccine candidate strain with two independent attenuating auxotrophic mutations in leucine and pantothenate biosynthesis. The deltaleuD deltapanCD double auxotroph is fully attenuated in the SCID mouse model and highly immunogenic and protective in the extremely sensitive guinea pig tuberculosis model, reducing both bacterial burden and disease pathology.

Inhibitors of pantothenate kinase: novel antibiotics for staphylococcal infections

Pantothenate kinase (CoaA) catalyzes the first step of the coenzyme A biosynthetic pathway. Here we report the identification of the Staphylococcus aureus coaA gene and characterization of the enzyme. We have also identified a series of low-molecular-weight compounds which are effective inhibitors of S. aureus CoaA.