Vitamin B6 Vitamers Research Articles

Exploration of Vitamin B6-Based Redox-Active Pyridinium Salts Towards the Application in Aqueous Organic Flow Batteries.

Pyridoxal hydrochloride, a vitamin B6 vitamer, was synthetically converted to a series of diverse redox-active benzoyl pyridinium salts. Cyclic voltammetry studies demonstrated redox reversibility under basic conditions, and two of the most promising salts were subjected to laboratory-scale flow battery tests involving galvanostatic cycling at 10 mM in 0.1 M NaOH. In these tests, the battery was charged completely, corresponding to the transfer of two electrons to the electrolyte, but no discharge was observed. Both CV analysis and electrochemical simulations confirmed that the redox wave observed in the experimental voltammograms corresponds to a two-electron process. To explain the irreversibility in the battery tests, we conducted bulk electrolysis with the benzoyl pyridinium salts, affording the corresponding benzylic secondary alcohols. Computational studies suggest that the reduction proceeds in three consecutive steps: first electron transfer (ET), then proton-coupled electron transfer (PCET) and finally proton transfer (PT) to give the secondary alcohol. 1H NMR deuterium exchange studies indicated that the last PT step is not reversible in 0.1 M NaOH, rendering the entire redox process irreversible. The apparent reversibility observed in CV at the basic media likely arises from the slow rate of the PT step at the timescale of the measurement.

Pleiotropic effects of PipX, PipY, or RelQ overexpression on growth, cell size, photosynthesis, and polyphosphate accumulation in the cyanobacterium Synechococcus elongatus PCC7942.

The cyanobacterial protein PipY belongs to the Pyridoxal-phosphate (PLP)-binding proteins (PLPBP/COG0325) family of pyridoxal-phosphate-binding proteins, which are represented in all three domains of life. These proteins share a high degree of sequence conservation, appear to have purely regulatory functions, and are involved in the homeostasis of vitamin B6 vitamers and amino/keto acids. Intriguingly, the genomic context of the pipY gene in cyanobacteria connects PipY with PipX, a protein involved in signaling the intracellular energy status and carbon-to-nitrogen balance. PipX regulates its cellular targets via protein-protein interactions. These targets include the PII signaling protein, the ribosome assembly GTPase EngA, and the transcriptional regulators NtcA and PlmA. PipX is thus involved in the transmission of multiple signals that are relevant for metabolic homeostasis and stress responses in cyanobacteria, but the exact function of PipY is still elusive. Preliminary data indicated that PipY might also be involved in signaling pathways related to the stringent stress response, a pathway that can be induced in the unicellular cyanobacterium Synechococcus elongatus PCC7942 by overexpression of the (p)ppGpp synthase, RelQ. To get insights into the cellular functions of PipY, we performed a comparative study of PipX, PipY, or RelQ overexpression in S. elongatus PCC7942. Overexpression of PipY or RelQ caused similar phenotypic responses, such as growth arrest, loss of photosynthetic activity and viability, increased cell size, and accumulation of large polyphosphate granules. In contrast, PipX overexpression decreased cell length, indicating that PipX and PipY play antagonistic roles on cell elongation or cell division. Since ppGpp levels were not induced by overexpression of PipY or PipX, it is apparent that the production of polyphosphate in cyanobacteria does not require induction of the stringent response.

Update on Interconversions of Vitamin B-6 with Its Coenzyme

Biosynthesis of pyridoxal 5’-phosphate (PLP) depends upon the relatively specific action of two consecutive enzymes, viz. pyridoxal (pyridoxine, pyridoxamine) kinase and pyridoxine (pyridoxamine) phosphate oxidase. Less specific phosphatases catalyze hydrolyses of the 5’-phosphates of the vitamers pyridoxal, pyridoxamine, and pyridoxine. From the recognition a generation ago of these processes by which the three forms of vitamin B-6 and their 5’-phosphates are interconverted, more recent studies have provided a fairly sophisticated understanding of the molecular characteristics of the enzymes involved. The evolutionary retention of homologous portions of pyridoxal kinase in humans as well as bacteria and the most recent finding of a highly conserved region of the pyridoxine (pyridoxamine) phosphate oxidase, also from both prokaryotic and eukaryotic organisms, emphasize the importance of these catalysts in the formation of a coenzyme that is essential for most organisms. Both kinase and oxidase involved in B-6 metabolism are potential targets for pharmacologic agents.

The Conserved Family of the Pyridoxal Phosphate-Binding Protein (PLPBP) and Its Cyanobacterial Paradigm PipY.

The PLPBP family of pyridoxal phosphate-binding proteins has a high degree of sequence conservation and is represented in all three domains of life. PLPBP members, of which a few representatives have been studied in different contexts, are single-domain proteins with no known enzymatic activity that exhibit the fold type III of PLP-holoenzymes, consisting in an α/β barrel (TIM-barrel), where the PLP cofactor is solvent-exposed. Despite the constant presence of cofactor PLP (a key catalytic element in PLP enzymes), PLPBP family members appear to have purely regulatory functions affecting the homeostasis of vitamin B6 vitamers and amino/keto acids. Perturbation of these metabolites and pleiotropic phenotypes have been reported in bacteria and zebrafish after PLPBP gene inactivation as well as in patients with vitamin B6-dependent epilepsy that results from loss-of-function mutations at the PLPBP. Here, we review information gathered from diverse studies and biological systems, emphasizing the structural and functional conservation of the PLPBP members and discussing the informative nature of model systems and experimental approaches. In this context, the relatively high level of structural and functional characterization of PipY from Synechococcus elongatus PCC 7942 provides a unique opportunity to investigate the PLPBP roles in the context of a signaling pathway conserved in cyanobacteria.

Validated UPLC-MS/MS method for the analysis of vitamin B6 pyridoxal 5́-phosphate, pyridoxal, pyridoxine, pyridoxamine, and pyridoxic acid in human cerebrospinal fluid

Vitamin B6 and its metabolites play a crucial role in the development and interaction of brain metabolism. Following diagnostic improvements additional inherited disorders in vitamin B6 metabolism have been identified, most of them leading to a severe epileptic disorder accompanied by progressive neurological deficits including intellectual disability and microcephaly. Since early treatment can improve the outcome, fast and reliable detection of metabolic biomarkers is important. Therefore, the analysis of vitamin B6 metabolites has become increasingly important, but is, however, still challenging and limited to a few specialized laboratories.Until today, vitamin B6 metabolites are measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) using trichloroacetic acid for protein precipitation. In this work, we present the development and validation of a new, accurate and reliable method for analysis and quantification of the vitamin B6 vitamers pyridoxal 5́-phosphate (PLP), pyridoxal (PL), pyridoxine (PN), pyridoxamine (PM) and pyridoxic acid (PA) in human CSF samples using acetonitrile for protein precipitation. The method is based on ultra-performance liquid chromatography-tandem mass spectrometry using electrospray ionization (UPLC-ESI-MS/MS). The calibration was performed in surrogate matrix Ringer solution and metabolites were quantified by their corresponding isotopically labelled internal standards. A protein precipitation by acetonitrile was applied greatly improving chromatographic separation of the metabolites in a 4.7 min chromatographic run. The method was validated following the European Medical Agency (EMA) and Food and Drug Administration (FDA) guidelines for bioanalytical method validation. The metabolites were quantified from 5 to 200 nmol/L with a seven-point calibration curve and minimum coefficient of regression of 0.99. The validation was performed with quality control samples at four concentration levels with surrogate matrix ringer solution and pooled CSF material. Within- and inter-day accuracy and precision in Ringer solution were within 85.4 % (PLP) and 114.5 % (PM) and from 2.6 % (PA) to 16.5 % (PLP). Within- and inter-day accuracy and precision in pooled CSF material were within 90.5 % (PN) and 120.1 % (PL) and from 1.7 % (PA) to 19.0 % (PM). The method was tested by measuring of 158 CSF samples to determine reference ranges. The B6 vitamers PLP and PL were determined in all CSF samples above 5 nmol/L while PN, PM and PA showed concentrations below or near LOQ. Probable supplementation of PLP was detected in eight CSF samples, which revealed high concentrations of PM, PN, PL, or PA, whereas PLP was in the reference range or slightly elevated. The method is suitable for the application within a routine diagnostic laboratory.

Increased vitamin B6 turnover is associated with greater mortality risk in the general US population: A prospective biomarker study

Vitamin B6 status and mortality risk are inversely associated in different patient groups, while prospective studies in the general population are lacking. Here, for the first time, we evaluated the association between biomarkers of vitamin B6 status and mortality risk in a large population-based study. The vitamin B6 vitamers pyridoxal-5'-phosphat (PLP) and 4-pyridoxic acid (4-PA) were measured by high-performance liquid chromatography in the National Health and Nutrition Examination Survey (NHANES) between 2005 and 2010. Participants' vital status and causes of death were recorded until December 2015. Multivariable Cox regression analyses were carried out to estimate Hazard Ratios (HRs) and 95% confidence intervals (CIs) of mortality across quintiles of PLP, 4-PA, and the ratio of 4-PA and PLP. Out of 15,304 study participants aged between 20 and 85 years at baseline, 1666 (7.7%) died during a median follow-up time of 7.8 years. An inverse association between PLP and mortality was found in a multivariable model adjusted for socioeconomic and lifestyle factors but became statistically non-significant upon adjustment for routine biomarkers (C-reactive protein, creatinine, albumin, and alkaline phosphatase). There was a significant linear trend for a positive association between 4-PA levels and mortality risk in the fully adjusted regression model, although a comparison of extreme quintiles (quintile 5 vs. quintile 1) did not show a significant difference (HRQ5vs.Q1 (95% CI): 1.19 (0.93, 1.51), plinear trend=0.02). A positive association between the 4-PA/PLP ratio and all-cause mortality was observed in the multivariable model, with an HRsQ5vs.Q1 of 1.45 (95% CI: 1.14, 1.85; plinear trend<0.0001). There were no significant associations between the biomarkers and cardiovascular or cancer mortality. The association between 4-PA/PLP and mortality risk was heterogeneous across age groups, and only statistically significant among participants older than 65 years at baseline (HRQ5vs.Q1 (95% CI): 1.72 (1.29, 2.29), plinear trend<0.0001). In this group, 4-PA/PLP was also associated with cancer mortality, with an HR Q5vs.Q1 of 2.16 (1.20, 3.90), plinear trend=0.02). Increased vitamin B6 turnover, as indicated by a higher 4-PA/PLP ratio, was associated with all-cause and cancer mortality among the older U.S. general population. Intervention trials are needed to assess whether older individuals with a high 4-PA/PLP ratio would benefit from increased vitamin B6 intake.

Loss of a pyridoxal-phosphate phosphatase rescues Arabidopsis lacking an endoplasmic reticulum ATP carrier.

The endoplasmic reticulum (ER)-located ATP/ADP-antiporter (ER-ANT1) occurs specifically in vascular plants. Structurally different transporters mediate energy provision to the ER, but the cellular function of ER-ANT1 is still unknown. Arabidopsis (Arabidopsis thaliana) mutants lacking ER-ANT1 (er-ant1 plants) exhibit a photorespiratory phenotype accompanied by high glycine levels and stunted growth, pointing to an inhibition of glycine decarboxylase (GDC). To reveal whether it is possible to suppress this marked phenotype, we exploited the power of a forward genetic screen. Absence of a so far uncharacterized member of the HaloAcid Dehalogenase (HAD)-like hydrolase family strongly suppressed the dwarf phenotype of er-ant1 plants. Localization studies suggested that the corresponding protein locates to chloroplasts, and activity assays showed that the enzyme dephosphorylates, with high substrate affinity, the B6 vitamer pyridoxal 5'-phosphate (PLP). Additional physiological experiments identified imbalances in vitamin B6 homeostasis in er-ant1 mutants. Our data suggest that impaired chloroplast metabolism, but not decreased GDC activity, causes the er-ant1 mutant dwarf phenotype. We present a hypothesis, setting transport of PLP by ER-ANT1 and chloroplastic PLP dephosphorylation in the cellular context. With the identification of this HAD-type PLP phosphatase, we also provide insight into B6 vitamer homeostasis.

Determination of Vitamin B3 Vitamer (Nicotinamide) and Vitamin B6 Vitamers in Human Hair Using LC-MS/MS.

Water-soluble B vitamins participate in numerous crucial metabolic reactions and are critical for maintaining our health. Vitamin B deficiencies cause many different types of diseases, such as dementia, anaemia, cardiovascular disease, neural tube defects, Crohn’s disease, celiac disease, and HIV. Vitamin B3 deficiency is linked to pellagra and cancer, while niacin (or nicotinic acid) lowers low-density lipoprotein (LDL) and triglycerides in the blood and increases high-density lipoprotein (HDL). A highly sensitive and robust liquid chromatography–tandem mass spectroscopy (LC/MS-MS) method was developed to detect and quantify a vitamin B3 vitamer (nicotinamide) and vitamin B6 vitamers (pyridoxial 5′-phosphate (PLP), pyridoxal hydrochloride (PL), pyridoxamine dihydrochloride (PM), pridoxamine-5′-phosphate (PMP), and pyridoxine hydrochloride (PN)) in human hair samples of the UAE population. Forty students’ volunteers took part in the study and donated their hair samples. The analytes were extracted and then separated using a reversed-phase Poroshell EC-C18 column, eluted using two mobile phases, and quantified using LC/MS-MS system. The method was validated in human hair using parameters such as linearity, intra- and inter-day accuracy, and precision and recovery. The method was then used to detect vitamin B3 and B6 vitamers in the human hair samples. Of all the vitamin B3 and B6 vitamers tested, only nicotinamide was detected and quantified in human hair. Of the 40 samples analysed, 12 were in the range 100–200 pg/mg, 15 in the range 200–500 pg/mg, 9 in the range of 500–4000 pg/mg. The LC/MS-MS method is effective, sensitive, and robust for the detection of vitamin B3 and its vitamer nicotinamide in human hair samples. This developed hair test can be used in clinical examination to complement blood and urine tests for the long-term deficiency, detection, and quantification of nicotinamide.

Effects of a Folic Acid 5 Mg Daily Intervention on Markers of Vitamin B Status and Kynurenine Pathway

BackgroundIn Brazil, most folic acid (FA) containing supplements contain 5 mg FA. This dose is usually prescribed for patients with chronic hemolytic anemia and for women planning pregnancy. The effects of high FA doses on vitamin B1, B2 and B6 status including the kynurenine pathway are still unclear.AimsTo assess the effects of a daily intervention with 5 mg FA in healthy subjects on vitamins B1, B2 and B6 serum marker status and serum concentration ok kynurenines.Material and MethodsThirty health subjects participated in a 5 mg/day FA intervention. Blood samples were obtained at baseline (D0) and after 45 (D45) and 90 days (D90) of intervention. We assessed serum concentrations of vitamin B6 (pyridoxal-5'-phosphate (PLP), pyridoxal (PL) and 4-pyridoxic acid (PA)), vitamin B2 (riboflavin and flavin mononucleotide (FMN)) and vitamin B1 vitamers (thiamine and thiamine monophosphate (TMP)), as well as tryptophan, kynurenine and several metabolites of tryptophan catabolism in the kynurenine pathway (3-hydroxykynurenine (HK), kynurenic acid (KA), anthranilic acid (AA), xanthurenic acid (XA), 3-hydroxyanthranilic acid (HAA), picolinic acid (Pic) and quinolinic acid (QA)) using LC-MS/MS. PA ratio (PAr) was calculated by PA/(PLP + PL). All variables were normalized by Box-Cox transformation. Comparisons were performed by repeated-measures ANOVA.ResultsConcentrations of all vitamin B6 vitamers (PLP, PL and PA), as well as PAr, were similar at baseline and D45 and D90 of FA intervention. No differences were found among serum vitamin B2 vitamers (riboflavin and FMN) after FA intervention. However, a trend for a decrease in serum TMP concentrations was observed at D90 (P = 0.054). No changes in serum tryptophan and all serum kynurenine pathway metabolites were observed after intervention with FA compared with baseline, except for AA, which was higher at D45 and D90 than baseline (P < 0.001).ConclusionOur data suggest that daily use of 5 mg FA by healthy subjects may interfere with vitamin B1 status markers. In addition, serum AA increased with FA intervention, which suggest that the use of high dose FA supplements might affect the kynurenine pathway.Financing: FAPESP (2016/18854-4) and CNPq (401586/2014-6) DisclosuresNo relevant conflicts of interest to declare.

Inhibiting Pyridoxal Kinase of Entamoeba histolytica Is Lethal for This Pathogen.

Pyridoxal 5’-phosphate (PLP) functions as a cofactor for hundreds of different enzymes that are crucial to the survival of microorganisms. PLP-dependent enzymes have been extensively characterized and proposed as drug targets in Entamoeba histolytica. This pathogen is unable to synthesize vitamin B6 via de-novo pathway and relies on the uptake of vitamin B6 vitamers from the host which are then phosphorylated by the enzyme pyridoxal kinase to produce PLP, the active form of vitamin B6. Previous studies from our lab shows that EhPLK is essential for the survival and growth of this protozoan parasite and its active site differs significantly with respect to its human homologue making it a potential drug target. In-silico screening of EhPLK against small molecule libraries were performed and top five ranked molecules were shortlisted on the basis of docking scores. These compounds dock into the PLP binding site of the enzyme such that binding of these compounds hinders the binding of substrate. Of these five compounds, two compounds showed inhibitory activity with IC50 values between 100-250 μM when tested in-vitro. The effect of these compounds proved to be extremely lethal for Entamoeba trophozoites in cultured cells as the growth was hampered by 91.5% and 89.5% when grown in the presence of these compounds over the period of 72 hours.

Comparative UHPLC-Q-Orbitrap HRMS-Based Metabolomics Unveils Biochemical Changes of Black Garlic during Aging Process.

Aged black garlic (BG) is a functional food in global markets; however, very few studies have ventured into comprehensive profiling of BG metabolomes during the aging process. Herein, we exploited UHPLC-Orbitrap HRMS for a comparative metabolomics analysis. During the heat treatment, organosulfur compounds such as allicin, diallyl disulfide, ajoene, S-allyl-l-cysteine (SAC), and γ-glutamyl-SAC were downregulated. Plenty of glycerophospholipids together with shikimate, aromatic amino acids, and vitamin B6 vitamers were significantly augmented; tryptophan was however consumed to generate downstream products manifested in nicotinate metabolism and aminobenzoate degradation. These secondary metabolites serve as signaling mediators or protectants against extreme thermal exposure. Besides, Heyns compounds and Amadori-rearrangement byproducts with potential mutagenic effects were concentrated. Together, our findings expand the known metabolome space of BG processing and better elucidate the reactivities of the key metabolites. We provide in-depth insights into the biochemical changes of BG that enable further functional or toxicological investigations of this popular food.

Pyridoxal, pyridoxamine, and pyridoxine cooking loss: Characterizing vitamin B 6 profiles of chicken meats before and after cooking

In the literature, the level of vitamin B6 in foods is given as sum of the pyridoxal (PL), pyridoxamine (PM), and pyridoxine (PN) forms. There is little information on vitamin B6 profiles in raw and cooked chickens. Since the levels of PL, PM, and PN forms of vitamin B6 are different in chickens, knowing the amount of these forms is essential after cooking. The PL, PM, PN, and total vitamin B6 concentrations in chickens were determined by HPLC. The cooking loss of total vitamin B6 was ranged between 55% and 89%, and the values were significantly higher than those reported previously. The PL and PM losses in chickens were ranged from 50% to 92% and from 70% to 96%, respectively. The PN was found to be negligible. This is the first report on the cooking loss of vitamin B6 vitamers in chicken meats commonly consumed in Turkey. Practical applications The present study aimed to reveal the potential vitamin B6 losses in chickens due to the widely used cooking methods. As a useful practical application for the food industry, this obtained results can be successfully integrated on the packages' surface, which can be easily seen from the consumers. Thus, the consumers can cook the foods depending on this cooking conditions and methods, especially at home. The loss of pyridoxal, pyridoxamine, and pyridoxine can be effectively protected by these practices at home and in the industrial applications.

Vitamin B6 Is Under a Tight Balance During Disease Development by Rhizoctonia solani on Different Cultivars of Potato and on Arabidopsis thaliana Mutants.

Vitamin B6 is well recognized as an essential antioxidant and plays a role in stress responses. Co-expression of plant and pathogen-derived vitamin B6 genes is critical during disease development of R. solani. However, little is known about the functionality of vitamin B6 vitamers during plant-R. solani interactions and their involvement in disease tolerance. Here, we explored the possible involvement of vitamin B6 during disease progression of potato cultivars of different susceptibility levels to R. solani. A distinct pattern of gene expression, pyridoxine (PN) concentration, and fungal biomass was found in the susceptible cv. Russet Burbank and tolerant cv. Chieftain. Accumulation of reactive oxygen species (ROS) in R. solani mycelia or plant tissues applying non-fluorescence or fluorescence methods was related to up-regulation in the vitamin B6 pathway and is indicative of oxidative stress. Russet Burbank was susceptible to R. solani, which was linked to reduced amounts of VB6 content. Prior to infection, constitutive PN levels were significantly higher in Russet Burbank by 1.6-fold compared to Chieftain. Upon infection with R. solani, PN levels in infected tissues increased more in Chieftain (1.7-fold) compared to Russet Burbank (1.4-fold). R. solani AG3 infection of potato sprouts in both cultivars significantly activates the fungal and plant vitamin B6 and glutathione-S-transferase (GST) genes in a tissue-specific response. Significant fold increases of transcript abundance of the fungal genes ranged from a minimum of 3.60 (RsolSG3GST) to a maximum of 13.91 (RsolAG3PDX2) in the surrounding necrotic lesion tissues (zone 1). On the other hand, PCA showed that the top plant genes STGST and STPDX1.1 were linked to both tissues of necrotic lesions (zone 2) and their surrounding areas of necrotic lesions. Functional characterization of Arabidopsis pdx1.3 mutants challenged with R. solani provided evidence into the role of the vitamin B6 pathway in the maintenance of plant tolerance during disease progression. Overall, we demonstrate that the production of vitamin VB6 is under tight control and is an essential determinant of disease development during the interaction of R. solani with potato cultivars.

Effects of Pyridoxine Deficiency on Hippocampal Function and Its Possible Association with V-Type Proton ATPase Subunit B2 and Heat Shock Cognate Protein 70.

Pyridoxine, one of the vitamin B6 vitamers, plays a crucial role in amino acid metabolism and synthesis of monoamines as a cofactor. In the present study, we observed the effects of pyridoxine deficiency on novel object recognition memory. In addition, we examined the levels of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), 3,4-dihydroxyphenethylamine (DA), 3,4-dihydroxyphenylacetic acid, and homovanillic acid and the number of proliferating cells and neuroblasts in the hippocampus. We also examined the effects of pyridoxine deficiency on protein profiles applying a proteomic study. Five-week-old mice fed pyridoxine-deficient diets for 8 weeks and showed a significant decrease in the serum and brain (cerebral cortex, hippocampus, and thalamus) levels of pyridoxal 5′-phosphate, a catalytically active form of vitamin-B6, and decline in 5-HT and DA levels in the hippocampus compared to controls fed a normal chow. In addition, pyridoxine deficiency significantly decreased Ki67-positive proliferating cells and differentiated neuroblasts in the dentate gyrus compared to controls. A proteomic study demonstrated that a total of 41 spots were increased or decreased more than two-fold. Among the detected proteins, V-type proton ATPase subunit B2 (ATP6V1B2) and heat shock cognate protein 70 (HSC70) showed coverage and matching peptide scores. Validation by Western blot analysis showed that ATP6V1B2 and HSC70 levels were significantly decreased and increased, respectively, in pyridoxine-deficient mice compared to controls. These results suggest that pyridoxine is an important element of novel object recognition memory, monoamine levels, and hippocampal neurogenesis. Pyridoxine deficiency causes cognitive impairments and reduction in 5-HT and DA levels, which may be associated with a reduction of ATP6V1B2 and elevation of HSC70 levels in the hippocampus.

A case of pyridoxine-dependent epilepsy with novel ALDH7A1 mutations.

Pyridoxine-dependent epilepsy (PDE) is a rare autosomal-recessive disorder typically presenting with neonatal seizures and is sometimes difficult to diagnose, because the clinical features mimic those of birth asphyxia. A Japanese newborn boy presented with pulmonary haemorrhage and convulsions on the day of birth. Brain computed tomography showed diffuse, but mild, low-density cerebral white matter and a thin subdural hematoma in the posterior fossa. He did not have thrombocytopenia or coagulopathy. His respiratory status improved with conservative treatment, but his convulsions were persistent even after prescription of several antiepileptic drugs. His serum and cerebrospinal fluid showed decreased vitamin B6 vitamers and increased upstream metabolites of α-aminoadipic semialdehyde dehydrogenase, strongly suggesting a diagnosis of PDE; the epileptic spasms ceased after administration of intravenous pyridoxal phosphate hydrate. Gene analysis revealed novel compound heterozygous mutations in ALDH7A1 that included NM_001182.4:[c.1196G > T] and [c.1200 + 1G > A]. Atypical birth asphyxia with persistent neonatal seizure should prompt vitamin B6/metabolite screening.

The vitamin B6-regulated enzymes PYGL and G6PD fuel NADPH oxidases to promote skin inflammation

Psoriasis is a skin inflammatory disorder that affects 3% of the human population. Although several therapies based on the neutralization of proinflammatory cytokines have been used with relative success, additional treatments are required. The in silico analysis of gene expression data of psoriasis lesional skin and an analysis of vitamin B6 metabolites in the sera of psoriasis patients point to altered vitamin B6 metabolism at both local and systemic levels. Functional studies showed that vitamin B6 vitamers reduced skin neutrophil infiltration, oxidative stress and Nfkb activity in two zebrafish models of skin inflammation. Strikingly, inhibition of glycogen phosphorylase L (Pygl) and glucose-6-phosphate dehydrogenase (G6pd), two vitamin B6-regulated enzymes, alleviated oxidative-stress induced inflammation in zebrafish skin inflammation models. Despite the central role of G6pd in antioxidant defenses, the results of the study demonstrate that glycogen stores and G6pd fuel NADPH oxidase to promote skin inflammation, revealing novel targets for the treatment of skin inflammatory disorders.

Ultraviolet-B radiation exposure lowers the antioxidant capacity in the Arabidopsis thaliana pdx1.3-1 mutant and leads to glucosinolate biosynthesis alteration in both wild type and mutant

Pyridoxine (vitamin B6) and its vitamers are used by living organisms both as enzymatic cofactors and as antioxidants. We used Arabidopsis pyridoxine biosynthesis mutant pdx1.3-1 to study the involvement of the PLP-synthase main polypeptide PDX1 in plant responses to ultraviolet radiation of two different qualities, one containing primarily UV-A (315–400 nm) and the other containing both UV-A and UV-B (280–315 nm). The antioxidant capacity and the flavonoid and glucosinolate (GS) profiles were examined. As an indicator of stress, Fv/Fm of photosystem II reaction centers was used. In pdx1.3-1, UV−A + B exposure led to a significant 5% decrease in Fv/Fm on the last day (day 15), indicating mild stress at this time point. The antioxidant capacity of Col-0 wildtype increased significantly (50–73%) after 1 and 3 days of UV−A + B. Instead, in pdx1.3-1, the antioxidant capacity significantly decreased by 44–52% over the same time period, proving the importance of a full complement of functional PDX1 genes for the detoxification of reactive oxygen species. There were no significant changes in the flavonoid glycoside profile under any light condition. However, the GS profile was significantly altered, both with respect to Arabidopsis accession and exposure to UV. The difference in flavonoid and GS profiles reflects that the GS biosynthesis pathway contains at least one pyridoxine-dependent enzyme, whereas no such enzyme is used in flavonoid biosynthesis. Also, there was strong correlation between the antioxidant capacity and the content of some GS compounds. Our results show that vitamin B6 vitamers, functioning both as antioxidants and co-factors, are of importance for the physiological fitness of plants.

Thiosemicarbazone ligand, nickel(II) and ruthenium(II) complexes based on vitamin B6 vitamer: The synthesis, different coordination behaviors and antioxidant activities

Mixed ligand nickel(II) and ruthenium(II) complexes were synthesized from pyridoxal-N-allyl-thiosemicarbazone hydrochloride and triphenylphosphine. The structures of the complexes have been characterized by elemental analysis, IR, 1H and 31P NMR, conductivity, magnetic moment measurements and single-crystal X-ray diffraction technique. Based on X-ray crystallographic studies, a square-planar structure has been proposed for the Ni(II) complex, in which the thiosemicarbazone ligand acts as dianionic tridentate ONS ligand. In the case of the Ru(II) complex, the thiosemicarbazone is coordinated to metal atom as a monoanionic bidentate NS donor ligand in an octahedral geometry. Antioxidant activities of the ligand and its metal complexes were calculated as their trolox equivalent antioxidant capacities (TEAC) by CUPRAC method and DPPH assay. Both the ligand and its metal complexes were found to be antioxidant and are much more antioxidant at least 2.1 times than trolox, even, ligand is 3.5 times greater than that of trolox according to CUPRAC. A linear correlation (correlation coefficient R2 = 0.9997) appeared between the obtained TEAC values by the two antioxidant assays.

Investigation of the Effects of the Fenoxaprop-p-Ethyl Herbicide and Salicylic Acid on the Ascorbic Acid and Vitamin B6 Vitamers in Wheat Leaves

Herbicides inhibit plant growth and development by various mechanisms, and oxidative stress is a common plant response to herbicide treatment. In a limited number of studies, it has been shown that vitamins are also strong antioxidants. It has been also known that salicylic acid (SA), a natural compound, plays a role in the activation of plant defences. This study examined the effects of the fenoxaprop-p-ethyl (FE) herbicide and SA on the ascorbic acid and B6 vitamers (pyridoxine, pyridoxal, and pyridoxamine) in wheat leaves. After the wheat plants were grown for 15 days, the leaves were subjected to FE, SA (0.05, 0.5 and 5 mM), and FE + SA treatments for 24, 48, and 72 h. Then, the leaves were cut, and levels of ascorbic acid and B6 vitamers were analyzed. The vitamin analyses were performed by means of HPLC. It was found that the FE has caused to increase the ascorbic acid level but generally to decrease in all three forms of vitamin B6. When FE and SA treatments are applied together, it has been revealed that SA regulates the increasing of ascorbic acid levels and the decreasing of B6 vitamers levels by bringing the control levels. It can be concluded that exogenous SA by its contribution on endogenous SA content could play an ameliorating role on herbicide tolerance and the negative effects of herbicides can be reduced on the crop condition by applying an appropriate exogenous SA concentration.

A Survey of Pyridoxal 5'-Phosphate-Dependent Proteins in the Gram-Positive Model Bacterium Bacillus subtilis.

The B6 vitamer pyridoxal 5′-phosphate (PLP) is a co-factor for proteins and enzymes that are involved in diverse cellular processes. Therefore, PLP is essential for organisms from all kingdoms of life. Here we provide an overview about the PLP-dependent proteins from the Gram-positive soil bacterium Bacillus subtilis. Since B. subtilis serves as a model system in basic research and as a production host in industry, knowledge about the PLP-dependent proteins could facilitate engineering the bacteria for biotechnological applications. The survey revealed that the majority of the PLP-dependent proteins are involved in metabolic pathways like amino acid biosynthesis and degradation, biosynthesis of antibacterial compounds, utilization of nucleotides as well as in iron and carbon metabolism. Many PLP-dependent proteins participate in de novo synthesis of the co-factors biotin, folate, heme, and NAD+ as well as in cell wall metabolism, tRNA modification, regulation of gene expression, sporulation, and biofilm formation. A surprisingly large group of PLP-dependent proteins (29%) belong to the group of poorly characterized proteins. This review underpins the need to characterize the PLP-dependent proteins of unknown function to fully understand the “PLP-ome” of B. subtilis.