Search Results (33)

NAD⁺ depletion is a defining feature of the aging cell, driven by a progressive decline in nicotinamide phosphoribosyltransferase (NAMPT) activity, the rate-limiting enzyme of the NAD⁺ salvage pathway. Pyrroloquinoline quinone (PQQ), a plant-derived redox-active quinone cofactor, elevates intracellular NAD⁺ by a mechanism that remains incompletely understood. We employed an integrated in silico approach combining molecular docking, density functional theory (DFT), and 100 ns molecular dynamics (MD) simulation to evaluate whether PQQ directly targets NAMPT. Docking against the NAMPT crystal structure (PDB: 7ENQ) yielded a binding free energy of −9.4 kcal/mol, with PQQ positioned in the allosteric activation site and forming hydrogen bonds at His191, Asp219, and Val242 together with π–π stacking at Tyr188, extending a known synthetic activator pharmacophore to a dietary ligand class. MM-GBSA analysis yielded binding free energy = −31.2 kcal/mol, confirming dominant electrostatic and van der Waals stabilization. In silico alanine mutagenesis of Tyr188 and Val242 reduced binding affinity to −7.2 and −7.0 kcal/mol respectively, with complete loss of allosteric-site contacts, validating the proposed mechanism computationally. DFT analysis revealed a HOMO–LUMO gap of 3.20 eV and electrophilicity index ω = 8.91 eV, consistent with non-covalent binding to nucleophilic residues. MD simulation confirmed retention of PQQ within the allosteric site over 100 ns. These data provide a structural and electronic framework for the NAD⁺-boosting activity of PQQ and a rationale for experimental validation. Full article

Asthma is a heterogeneous chronic airway disease in which oxidative stress (OS) plays a central mechanistic role beyond classical immune-mediated inflammation. Reactive oxygen and nitrogen species (ROS/RNS), generated by recruited inflammatory cells and activated airway structural cells, drive epithelial injury, mucus hypersecretion, airway remodeling, and modulate key transcription factors including nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. This review synthesizes current evidence on the multilevel redox-based determinants of asthma severity, spanning from genetic polymorphisms to circulating biomarkers. We examine serum antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), peroxiredoxins (PRDXs), and the thioredoxin (Trx) system as dynamic indicators of systemic redox status and disease severity, alongside oxidative enzymes including NADPH oxidases and dual oxidases (NOX/DUOX), xanthine oxidase (XO), and myeloperoxidase (MPO) that serve as upstream sources of airway oxidant burden. Functional genetic polymorphisms in antioxidant genes (SOD2, CAT, glutathione S-transferase mu 1/glutathione S-transferase theta 1 (GSTM1/GSTT1), heme oxygenase-1 (HO-1), NAD(P)H quinone dehydrogenase 1 (NQO1), nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/KEAP1)) and oxidative enzyme genes including nitric oxide synthase 1/2/3 (NOS1/2/3), MPO, cytochrome b-245 alpha chain (CYBA), and xanthine dehydrogenase (XDH) are reviewed as modulators of individual redox capacity and asthma susceptibility, with particular attention to gene–environment interactions. We further discuss oxidative damage biomarkers, including malondialdehyde (MDA), 8-isoprostanes, 4-hydroxynonenal, 8-oxo-7, 8-dihydro-2′-deoxyguanosine, protein carbonyls, 3-nitrotyrosine, and advanced oxidation protein products as indicators of lipid, DNA, and protein oxidation that correlate with disease activity and control. The roles of micronutrient cofactors in modulating antioxidant enzyme function and their potential as contextual biomarkers are also addressed. Additionally, emerging evidence on microRNAs (miRNAs) linked to OS biology in asthma is presented. Finally, we critically evaluate the challenges limiting clinical translation, including biomarker non-specificity, analytical variability, gene–environment complexity, and the absence of standardized reference ranges. This integrated framework supports the development of multilevel redox prognostic panels combining genetic, enzymatic, and oxidative damage readouts for improved asthma phenotyping, severity stratification, and personalized therapeutic approaches. Full article

Background: Pyrroloquinoline quinone (PQQ), a naturally occurring redox cofactor with potent antioxidant and anti-inflammatory properties, has been shown to protect against cardiac injury. However, its therapeutic potential in diabetic cardiomyopathy (DCM) induced by Type 2 diabetes mellitus (T2DM) and the underlying mechanisms remain poorly understood. Methods: A T2DM mouse model was established via a high-fat diet and low-dose STZ. We investigated the cardioprotective effects of 12-week oral PQQ administration, assessing fasting blood glucose, oral glucose tolerance, cardiac function, myocardial histopathology, blood biochemistry, mitophagy, and NLRP3 inflammasome activation. In vitro experiments using AC16 cardiomyocytes exposed to palmitic acid and high glucose were also conducted. Results: Results showed PQQ significantly improved cardiac function, attenuated remodeling, and reduced proinflammatory cytokines in mice with T2DM, regulated key mitophagy-related proteins (Parkin, Beclin-1, LC3B-II, p62), and downregulated NLRP3 inflammasome pathway components (Caspase-1, NLRP3, IL-1β, IL-18). In vitro experiments demonstrated that PQQ reduced reactive oxygen species (ROS) production, improved mitochondrial membrane potential, promoted mitophagy, and inhibited NLRP3 inflammasome-mediated pyroptosis. Conclusions: PQQ alleviates DCM in mice with T2DM by improving mitochondrial quality control, promoting mitophagy, and subsequently inhibiting NLRP3 inflammasome-mediated pyroptosis, highlighting its potential as a promising therapeutic agent for T2DM-associated cardiomyopathy. Full article

Deoxynivalenol (DON), a Group III carcinogenic mycotoxin frequently detected in cereals and animal-derived food products, poses serious health risks to animals and humans. In this study, we developed a genetically engineered Saccharomyces cerevisiae strain as a proof-of-concept platform for DON detoxification. The yeast was engineered to co-express two detoxification genes, YTDepA and YTDepB (homologs of DepA and DepB from Devosia mutans 17-2-E-8) originally identified in Youhaiella tibetensis. Concurrently, the pyrroloquinoline quinone (PQQ) biosynthesis gene cluster from Klebsiella pneumoniae was integrated to supply the essential cofactor. Gene expression was verified by qRT-PCR and Western blot. The recombinant strain demonstrated a significant 13.98% detoxification of DON after 72 h of fermentation (p < 0.05), as confirmed by HPLC–MS, while the strain expressing only the PQQ cluster showed no detoxification activity. This study establishes an integrated yeast cell factory for DON detoxification and highlights key limitations to guide future optimization efforts. Full article

Chlorobaculum tepidum ferredoxin: ${\mathrm{NADP}}^{+}$ oxidoreductase (CtFNR) is a dimeric thioredoxin reductase (TrxR)-type FNR, whose mechanism and redox properties are poorly characterized. In this work, we focused on the reoxidation mechanisms of its flavin adenine dinucleotide (FAD) cofactor using quinones (Q), nitroaromatics (${\mathrm{ArNO}}_2$), and other nonphysiological oxidants with different single-electron reduction midpoint potentials ($E_7^1$) and electrostatic charge. Like in other FNRs, the rate-limiting step of the reaction is the reoxidation of FAD semiquinone (${\mathrm{FADH}}^{•}$). However, only one FAD per dimer functions in CtFNR due to some nonequivalence of the NADP(H) binding domains in separate subunits. The reactivity of Q increases with increasing $E_7^1$, while ${\mathrm{ArNO}}_2$ form another analogous series of lower reactivity. The compounds are reduced in a dominant single-electron way. These data are consistent with an “outer sphere” electron transfer mechanism. On the basis of reactions with 3-acetylpyridine adenine dinucleotide phosphate, the two-electron reduction midpoint potential of FAD at pH 7.0 is −0.282 V. In CtFNR, 11% ${\mathrm{FADH}}^{•}$ was stabilized at equilibrium. Calculated electron transfer distances in reactions with Q and ${\mathrm{ArNO}}_2$ were in the range of 2.6–3.4 Å. Taken together with previous studies of Rhodopseudomonas palustris and Bacillus subtilis FNRs, this work allows us to generalize the information on the catalytic ant thermodynamic properties of TrxR-type FNRs. In addition, our data may be valuable from an applied perspective, e.g., the use of redox mediators in photobioelectrochemical systems or microbial cells based on anoxygenic phototrophic bacteria. Full article

Redox mediators are central to electrochemical biosensors, enabling electron transfer between deeply buried enzymatic cofactors and electrode surfaces when direct electron transfer is kinetically inaccessible. Among all design parameters, the reversibility of mediator redox cycling remains the most decisive yet under-examined factor governing biosensor stability, drift and long-term reproducibility. This review establishes reversibility as a unifying framework grounded in inorganic and organometallic redox chemistry, with particular emphasis on coordination environments, ligand-field effects and outer-sphere electron-transfer pathways. Recent advances (2010–2025) in ruthenium and osmium polypyridyl complexes, cobalt macrocycles, hexacyanoferrates and Prussian Blue analogues are examined alongside ferrocene derivatives and other organometallic mediators, which together define the upper limits of reversible behaviour. Organic mediator families, including quinones, phenazines, indophenols, aminophenols and viologens, are discussed as mechanistic contrasts that highlight the structural and thermodynamic constraints that limit long-term cycling in aqueous media. Mechanistic indicators of reversibility, including peak separation, current ratios and heterogeneous electron-transfer rate constants, are linked to mediator architecture, coordination chemistry and immobilisation environment. By integrating molecular electrochemistry with applied sensor engineering, this review provides a mechanistically grounded basis for selecting or designing redox mediators that sustain efficient electron transfer, minimal fouling and calibration stability across diverse sensing platforms. Full article

Testicular torsion–detorsion (T/D) induces ischemia–reperfusion injury, leading to mitochondrial dysfunction, oxidative stress, apoptosis, and spermatogenic impairment. Pyrroloquinoline quinone (PQQ), a redox cofactor with mitochondrial-protective, antioxidant, and anti-apoptotic properties, was evaluated for its therapeutic potential in a rat T/D model. Young adult male Sprague-Dawley rats underwent 720° spermatic cord rotation for 2 h followed by detorsion and were assigned to T/D or T/D + PQQ groups, with sham-operated controls run in parallel. PQQ (400 mg/kg body weight) was administered orally once daily for 4 weeks. T/D resulted in severe disruption of testicular architecture, disorganization of seminiferous epithelium, reduced sperm count and testis-to-body weight ratio, increased hypoxia-inducible factor-1α and malondialdehyde, decreased superoxide dismutase 2, impaired oxidative phosphorylation (OXPHOS), and enhanced apoptosis. Notably, PQQ treatment significantly preserved testicular structure, improved sperm counts, reduced oxidative stress, restored OXPHOS, and suppressed apoptosis (all p < 0.05. T/D + PQQ vs. T/D). These findings indicate that PQQ protects against T/D-induced testicular injury. The underlying mechanisms may involve the attenuation of oxidative stress, the preservation of mitochondrial function, and the limitation of apoptosis, supporting its potential as a therapeutic strategy for testicular IRI. Full article

Mitochondrial metabolism in the trabecular meshwork (TM) plays a critical role in maintaining intraocular pressure homeostasis by supporting the energy-demanding processes involved in aqueous humour outflow. In primary open-angle glaucoma, oxidative stress impairs mitochondrial function, leading to TM dysfunction. Therefore, understanding and targeting mitochondrial health in TM cells could offer a novel therapeutic strategy. Pyrroloquinoline quinone (PQQ) is a redox cofactor with antioxidant and mitochondrial-enhancing properties. However, its effects on human TM (HTM) cells remain largely unexplored. This study examined PQQ cytoprotective effects against H₂O₂-induced oxidative stress in HTM cells. Seahorse analyses revealed that PQQ alone improves mitochondrial respiration and ATP production. Moreover, PQQ mitigates H₂O₂-induced cellular damage and preserves mitochondrial function by normalising proton leak and increasing ATP levels. Furthermore, TEM and confocal microscopy showed that PQQ can partially alleviate structural damage, restoring mitochondrial network morphology, thereby leading to reduced cell death. Although these protective effects seem not to be mediated by changes in mitochondrial content or activation of the SIRT1/PGC1-α pathway, they may involve modulation of SIRT3, a key factor of mitochondrial metabolism and homeostasis. Overall, these results suggest that PQQ may represent a promising candidate for restoring mitochondrial function and reversing oxidative damage in HTM cells. Full article

Nanoquenchers with a single quenching cofactor exhibit limited fluorescence quenching efficiency. In this work, a metal–organic hybrid with dual quenching cofactors (Cu²⁺ and pyrroloquinoline quinone or PQQ) was prepared by metal-coordinated assembly and used as a nanoquencher for a protease assay with enhanced quenching efficiency. The peptide substrate with an oligohistidine (His₆) tag was labeled with a fluorophore. Caspase-3 was determined as a protease example. The substrate was attached onto the surface of the Cu-PQQ nanoquencher by a metal coordination interaction between the unsaturated Cu²⁺ on the nanoparticle surface and the His₆ tag in the peptide. The cleavage of the peptide substrate by enzymatic hydrolysis led to the release of a fluorophore-conjugated segment from the nanoquencher surface, thus turning on the fluorescence. The nanoprobe was used to determine caspase-3 with a linear range of 0.01–5 ng/mL and a detection limit of 7 pg/mL. Furthermore, the method was used to evaluate inhibition efficiency and monitor drug-induced cell apoptosis. In contrast to other means of peptide immobilization, such as physical adsorption and covalent coupling, the strategy based on the metal coordination interaction is simple and powerful, thereby achieving assays of caspase-3 activity in lysates with a satisfactory result. The work should be valuable for the design of nanoquenchers with multiple quenching cofactors and the development of novel biosensors. Full article

Background/Objectives: Clavulanic acid (CA) is produced by cell suspension cultures of Streptomyces clavuligerus ATCC 27064, and is widely used as a beta-lactamase inhibitor to combat antibiotic resistance. CA titers are moderate due to bioprocess complexity, prompting ongoing efforts to overcome these limitations. Methods: In this study, we aimed to evaluate the effect of live and inactivated Bacillus velezensis FZB42 cells on CA production in S. clavuligerus, and to explore the transcriptional response underlying this interaction using RNA-seq technology. Results: The addition of dead and live cells of B. velezensis improved CA production by 1.4 and 2.0-fold, respectively. Furthermore, the transcriptome of S. clavuligerus, obtained with live cells of B. velezensis FZB42 at the peak of maximum CA production, revealed that 410 genes were up-regulated and 594 were down-regulated under these conditions, with a padj < 0.05. Most of the genes from the cephamycin C and CA clusters were up-regulated, which correlates well with the increase in CA production. Likewise, S. clavuligerus ATCC 27064 enhanced the expression of genes encoding enzymes that scavenge endogenous H₂O₂, as well as other genes related to oxidative stress defense. Regarding downregulated genes, we found that S. clavuligerus decreased the expression of genes involved in the biosynthesis of terpenoids, polyketides, and lantibiotics, as well as the expression of the operon involved in the synthesis of the pyrroloquinoline quinone (PQQ) cofactor. Conclusions: These findings contribute to the understanding of S. clavuligerus metabolism and pave the way for future metabolic engineering efforts aimed at obtaining CA-overproducing strains. Full article

Matcha is a very popular tea food around the world, being widely used in the food, beverage, health food, and cosmetic industries, among others. At present, matcha shade covering methods, matcha superfine powder processing technology, and digital evaluations of matcha flavor quality are receiving research attention. However, research on the differences in flavor and quality characteristics of matcha from the same tea tree variety from different typical regions in China is relatively weak and urgently required. Taking Japan Shizuoka matcha (R) as a reference, the differences in sensory quality characteristics and non-volatile substances of matcha processed with the same tea variety from different regions in China were analyzed. The samples were China Hangzhou matcha (Z1), China Wuyi matcha (Z2), China Enshi matcha (H), and China Tongren matcha (G), which represent the typical matcha of eastern, central, and western China. A total of 1131 differential metabolites were identified in the matcha samples, comprising 118 flavonoids, 14 tannins, 365 organic acids, 42 phenolic acids, 22 alkaloids, 39 saccharides, 208 amino acids and derivatives, 17 lignans and coumarins, seven quinones, 44 nucleotides and derivatives, 14 glycerophospholipids, two glycolipids, 15 alcohols and amines, 140 benzenes and substituted derivatives, 38 terpenoids, 30 heterocyclic compounds, and 15 lipids. Kaempferol-7-O-rhamnoside, 3,7-Di-O-methylquercetin, epigallocatechin gallate, epicatechin gallate, and epigallocatechin were detected in Z1, Z2, H, and G. A total of 1243 metabolites differed among Z1, Z2, and R. A total of 1617 metabolites differed among G, H, and R. The content of non-volatile difference metabolites of Z2 was higher than that of Z1. The content of non-volatile difference metabolites of G was higher than that of H. The 20 key differential non-volatile metabolites of Z1, Z2, G, and H were screened out separately. The types of non-volatile flavor differential metabolites of G and H were more numerous than those of Z1 and Z2. The metabolic pathways, biosynthesis of secondary metabolites, biosynthesis of co-factors, flavonoid biosynthesis, biosynthesis of amino acids, biosynthesis of various plant secondary metabolites, and purine metabolism of metabolic pathways were the main KEGG pathways. This study provides new insights into the differences in metabolite profiles among typical Chinese matcha geographic regions with the same tea variety. Full article

Monascus species are capable of producing various active metabolites, including monacolin K (MK) and pigments. Studies have shown that the overexpression of the mok I gene from the MK synthesis gene cluster in Monascus species can significantly increase MK production; however, the molecular mechanism has not yet been fully elucidated. Therefore, this study focused on the mok I gene of Monascus pilosus to construct overexpression strains of the mok I gene, resulting in high-yield MK production. Sixteen positive transformants were obtained, seven of which produced 9.63% to 41.39% more MK than the original strain, with no citrinin detected in any of the transformants. The qRT-PCR results revealed that the expression levels of mok I in the transformed strains TI-13, TI-24, and TI-25 increased by more than 50% compared to the original strain at various fermentation times, with the highest increase being 10.9-fold. Furthermore, multi-omics techniques were used to analyze the molecular mechanisms underlying enhanced MK production in transformed strains. The results indicated that mok I overexpression may enhance MK synthesis in M. pilosus by regulating the expression of key genes (such as MAO, HPD, ACX, and PLC) and the synthesis levels of key metabolites (such as delta-tocopherol and alpha-linolenic acid) in pathways linked to the biosynthesis of cofactors, the biosynthesis of unsaturated fatty acids, tyrosine metabolism, ubiquinone and other terpenoid-quinone biosynthesis, alpha-linolenic acid metabolism, and glycerophospholipid metabolism. These findings provide a theoretical basis for further study of the metabolic regulation of MK in Monascus species and for effectively enhancing their MK production. Full article

Camellia luteoflora is a rare and endangered plant endemic to China. It has high ornamental and potential economic and medicinal value, and is an important germplasm resource of Camellia. To understand the distributions and differences in metabolites from different parts of C. luteoflora, in this study, we used liquid chromatography–tandem mass spectrometry (LC–MS/MS) to examine the types and contents of chemical constituents in five organs of C. luteoflora: roots, stems, leaves, flowers, and fruits. The results showed that a total of 815 metabolites were identified in the five organs and were classified into 18 main categories, including terpenoids (17.1%), amino acids (10.4%), flavonoids (10.3%), sugars and alcohols (9.8%), organic acids (9.0%), lipids (7.1%), polyphenols (4.8%), alkaloids (4.8%), etc. A total of 684 differentially expressed metabolites (DEMs) in five organs were obtained and annotated into 217 KEGG metabolic pathways, among which metabolic pathways, ABC transporters, the biosynthesis of cofactors, and the biosynthesis of amino acids were significantly enriched. In DEMs, flowers are rich in flavonoids, polyphenols, organic acids, and steroids; fruits are rich in amino acids, alkaloids, vitamins, and xanthones; stems are rich in lignans; and leaves have the highest relative content of phenylpropanoids, ketoaldehydic acids, quinones, sugars and alcohols, terpenoids, coumarins, lipids, and others; meanwhile, the metabolite content is lower in roots. Among the dominant DEMs, 58 were in roots, including arachidonic acid, lucidone, isoliquiritigenin, etc.; 75 were in flowers, including mannose, shikimic acid, d-gluconic acid, kaempferol, etc.; 45 were in the fruit, including pterostilbene, l-ascorbic acid, riboflavin, etc.; 27 were in the stems, including salicylic acid, d-(-)-quinic acid, mannitol, (-)-catechin gallate, etc.; there was a maximum number of 119 dominant metabolites in the leaves, including oleanolic acid, l-glucose, d-arabitol, eugenol, etc. In sum, the rich chemical composition of C. luteoflora and the significant differences in the relative contents of metabolites in different organs will provide theoretical references for the study of tea, flower tea, edible oil, nutraceuticals, and the medicinal components of C. luteoflora. Full article

Abstract: Interest in glutinous rice consumption has been expanding in East Asia. However, the extent of metabolite variation between common and glutinous rice has not been fully explored to identify metabolic targets for rice quality improvement. Thus, the objective of this study was to provide insights into the variation of metabolites and nutraceuticals between common and glutinous rice. Two black rice (common rice, BL-N, and glutinous rice, BL-G) and two white rice (common rice, WH-N, and glutinous rice, WH-G) types were analysed via LC-MS-based widely targeted metabolic profiling. We identified 441 and 343 types, including 160 key overlapping differentially accumulated metabolites between BL-N_vs_BL-G and WH-N_vs_WH-G, respectively. Glutinous rice showed a higher relative content of most categories of metabolites, except for quinones (in BL-N) and tannins (in WH-N). Seven vitamins, including B6, B3, B5, B13, isonicotinic acid, N-(beta-D-glucosyl)nicotinate, and 4-pyridoxic acid-O-glucoside, were significantly up-regulated in BL-G compared to BL-N. The biosynthesis of cofactors, zeatin biosynthesis, citrate cycle, amino acid metabolism, alpha-linolenic acid metabolism, and glyoxylate and dicarboxylate metabolism was the most differentially regulated pathway. Key differential metabolites in citrate cycle include citrate, isocitrate, fumarate, malate, succinate, and 2-oxoglutarate; in amino acid metabolism (L-serine, L-cysteine, L-lysine, L-glutamine, L-methionine, and L-tryptophan); and in glycolysis (UDP-glucose, D-glucose-1P, D-glucose-6P, and D-fructose-6P). The data resources in this study may contribute to a better understanding of the function and nutritional value of glutinous rice. Full article

Bacillus subtilis ferredoxin:NADP⁺ oxidoreductase (BsFNR) is a thioredoxin reductase-type FNR whose redox properties and reactivity with nonphysiological electron acceptors have been scarcely characterized. On the basis of redox reactions with 3-acetylpyridine adenine dinucleotide phosphate, the two-electron reduction midpoint potential of the flavin adenine dinucleotide (FAD) cofactor was estimated to be −0.240 V. Photoreduction using 5-deazaflavin mononucleotide (5-deazaFMN) as a photosensitizer revealed that the difference in the redox potentials between the first and second single-electron transfer steps was 0.024 V. We examined the mechanisms of the reduction of several different groups of non-physiological electron acceptors catalyzed by BsFNR. The reactivity of quinones and aromatic N-oxides toward BsFNR increased when increasing their single-electron reduction midpoint redox potentials. The reactivity of nitroaromatic compounds was lower due to their lower electron self-exchange rate, but it exhibited the same trend. A mixed single- and two-electron reduction reaction was characteristic of quinones, whereas reactions involving nitroaromatics proceeded exclusively via the one-electron reduction reaction. The oxidation of FADH^• to FAD is the rate-limiting step during the oxidation of fully reduced FAD. The calculated electron transfer distances in the reaction with nitroaromatics were close to those of other FNRs including the plant-type enzymes, thus demonstrating their similar active site accessibility to low-molecular-weight oxidants despite the fundamental differences in their structures. Full article