Search Results (70)

Agmatinase (SpeB) catalyzes the hydrolysis of agmatine to produce putrescine, a key step in bacterial polyamine biosynthesis. Here, we report the crystal structure of SpeB from Klebsiella pneumoniae (kpSpeB) and characterize its oligomeric and active-site architecture. SEC–MALS analysis demonstrates that kpSpeB forms a canonical hexamer in solution. Structural comparison reveals high similarity to Escherichia coli SpeB and other members of the arginase superfamily, including proclavaminic acid amidino hydrolase (PAH) and guanidine hydrolase (GdmH). Despite strong conservation of residues coordinating the binuclear Mn²⁺ center, subtle differences in metal positioning and cavity geometry were observed. Surface analysis indicates variations in active-site cavity volume among homologues, with partial occlusion in GdmH due to a bulky tryptophan residue. These findings suggest that minor adjustments in metal coordination and cavity architecture may fine-tune substrate selectivity while preserving the conserved catalytic framework of the arginase superfamily. Full article

Specific Learning Disability (SLD) describes persistent difficulties in academic skills in reading, writing, and mathematics, despite having normal intelligence. The exact origin of SLD is unknown. However, it is thought that biological factors and environmental conditions, along with genetic factors, contribute to the development of SLD. Agmatine, a neurotransmitter in the brain, plays a role in various biological processes. Agmatine has been reported to mediate antidepressant effects and neuroprotective effects, and it plays critical roles in learning and the processing of learned information into memory. Therefore, this study aimed to determine the relationship between SLD and agmatine metabolism by determining the enzyme levels of arginine decarboxylase (ADC) and agmatinase (AGMAT) in children with SLD. ADC and AGMAT levels in the blood serum of children with SLD and controls were analyzed using ELISA. When ADC levels in children with SLD (30.26 ± 5.06 ng/mL) were compared with those in the control group (29.82 ± 4.95 ng/mL), the difference was not statistically significant (p = 0.737). However, AGMAT levels in children with SLD (27.02 ± 4.46 ng/mL) were found to be statistically significantly higher than those in the control group (21.42 ± 3.98 ng/mL) (p < 0.001). In light of these findings, we can say that agmatine breakdown is significantly increased in children with SLD. Full article

Vibrio anguillarum is a major pathogenic bacterium causing vibriosis in aquatic animals, leading to substantial economic losses in the global aquaculture industry. Previous studies have indicated that L-arginine modulates the virulence of the pathogen, but the underlying molecular mechanisms remain elusive. The present study aimed to clarify the regulatory role of L-arginine metabolism in V. anguillarum virulence. We first evaluated the effects of L-arginine and its major metabolites (agmatine, putrescine, spermine) on the hemolytic activity of V. anguillarum. Results showed that L-arginine and its metabolites regulated hemolytic activity in a concentration-dependent biphasic manner, with agmatine exerting the most potent promoting effect. To identify the critical metabolic branch involved, four isogenic mutants were constructed targeting key genes in arginine metabolism (adc, astA, astD). Phenotypic analysis revealed that only the adc deletion mutant (Δadc) exhibited near-complete loss of hemolytic activity, which was dose-dependently restored by supplementation with agmatine, putrescine, or spermine. Transcriptomic analysis identified 704 significantly differentially expressed genes (DEGs) between Δadc and WT strains, with downregulated DEGs enriched in virulence-associated pathways. Key hemolysin and secretion system genes were validated to be downregulated in ∆adc by quantitative real-time PCR (qRT-PCR). Additionally, Δadc displayed attenuated anti-phagocytic ability in Tetrahymena co-culture assays, impaired biofilm formation, and increased susceptibility to multiple classes of antibiotics. Collectively, our findings demonstrate that L-arginine modulates V. anguillarum hemolysis and overall virulence through the adc-mediated agmatine biosynthesis branch. This study fills the knowledge gap in the regulatory mechanism of L-arginine on V. anguillarum virulence and provides a potential target for the control of vibriosis in aquaculture. Full article

Nitrite is a common toxic substance in aquaculture, and microplastics are environmental pollutants capable of adsorbing small molecules/particles. Shrimp rely mainly on the hepatopancreas to accomplish detoxification metabolism. In this study, we investigated the individual and combined effects of nitrite and microplastics on the physiological function of the P. vannamei hepatopancreas. The results demonstrated that both nitrite and microplastics induced morphological damage, with the combined stress exacerbating tissue damage. Oxidative stress biochemical indicators were disrupted, and most enzyme activities and gene expression levels were upregulated to varying degrees in each experimental group. The expression levels of immune genes (cytC, CASP-3, Crus, ALF, and proPO), detoxification metabolism genes (CYP450, EH1, SULT, and UGT), and oxidative-stress-related genes (ROMO1, SOD, GPx, and Trx) exhibited different fluctuations. Nitrite and microplastic stress resulted in altered hepatopancreatic function, mainly involving amino acid biosynthesis and metabolism, ABC transporters, oxidative phosphorylation, and the mTOR pathway. We identified 17 metabolic biomarkers, including 6 lipids (Oleic acid, Prostaglandin G2, Linoleic acid, Palmitic acid, Docosahexaenoic acid, Docosapentaenoic acid), 6 amino acids (L-Leucine, Agmatine, L-Arginine, L-Tyrosine, Ornithine, N-Acetylornithine), and 5 carbohydrates (Glyceric acid, Citric acid, D-Mannose, Sorbitol, Fumaric acid). These findings suggest that nitrite and microplastic stresses cause hepatopancreatic tissue damage and induce oxidative stress, physiological and metabolic dysfunction in the shrimp P. vannamei, thereby impacting its normal physiological functions. Full article

Tumbling pigeons are prone to oxidative stress and disruption of gut microbiota balance during long-term exercise training and competitions. Considering that Portulaca oleracea (P. oleracea), as a natural plant feed additive, has natural antioxidant, anti-inflammatory, and gut function improvement effects. This study investigates the effects of adding P. oleracea into health care sand on nutrient digestion and metabolism, serum parameters, and excreta microbiota metabolism in tumbler pigeons. Ninety 12-month-old tumbler pigeons were randomly assigned to three groups, with ten cages with three birds each. The CON Group received a basal diet added with 4 g of health care sand; Group TRT1 received a basal diet added with 4 g of health care sand containing 0.75% P. oleracea; and Group TRT2 received a basal diet added with 4 g of health care sand containing 1.00% Portulaca oleracea. The adaptation period lasted for 7 days, followed by a formal testing phase of 45 days. All tumbler pigeons received 1 h of flight training daily. The CON and TRT2 groups showed significantly increased dry matter (DM) apparent digestibility by 11.68% (p < 0.01) and 8.50% (p < 0.05), respectively, compared to the TRT1 group. The TRT2 group also demonstrated higher organic matter (OM) apparent digestibility (increase of 4.25%, p < 0.05) and markedly improved crude protein (CP) digestibility (16.72% higher than CON, p < 0.05; 27.12% higher than TRT1, p < 0.01). Both gross energy (GE) and metabolizable energy (ME) digestibility were significantly elevated in CON and TRT2 groups compared to TRT1 (p < 0.01). Compared to the CON group, the TRT2 group showed a 19.86% decrease in lactate (LAC) level (p < 0.05) alongside a 38.91% increase in lactate dehydrogenase (LDH) activity (p < 0.05). Serum uric acid (UA) levels increased by 33.65–36.14% in both treatment groups (p < 0.05). Antioxidant capacity markedly improved, with malondialdehyde (MDA) decreasing by up to 27.75% (p < 0.01) and key antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and total antioxidant capacity (T-AOC) showing dose-dependent enhancements of up to 25.23% (p < 0.01). Other serum biochemical parameters showed no significant differences (p > 0.05). Microbial analysis demonstrated that Actinobacteriota, Acidothermaceae, and Nitrosotaleaceae were enriched in the TRT1 and TRT2 groups, while the relative abundance of Proteobacteria and Chitinophagaceae decreased (p > 0.05). Metabolomic analysis revealed a significant increase in beneficial metabolites, including agmatine, pyropheophorbide-a, and N-acetylmuramate (p < 0.01). In conclusion, the addition of 1.00% Portulaca oleracea in health care sand effectively enhanced apparent nutrient digestibility, improved antioxidant capacity, and modulated the intestinal microbiota and metabolic profile of tumbler. Full article

Agmatine is a biogenic amine that functions as a neurotransmitter and exhibits anticonvulsant, antineurotoxic, and antidepressant properties. It can be metabolized into putrescine and urea by canonical agmatinases or by the agmatinase-like protein (ALP), which corresponds to the C-terminal region of the LIMCH1 protein. The amino acid sequence of ALP/LIMCH1 diverges significantly from that of canonical agmatinases and lacks the conserved residues typically required for coordination with Mn²⁺, an essential cofactor for ureohydrolase activity. The three-dimensional structure of ALP/LIMCH1 remains unresolved, and predictive artificial intelligence algorithms such as AlphaFold have failed to model it reliably. As a result, the configuration of its active site and the identity of potential metal-coordinating ligands remain elusive. In this study, we purified recombinant full-length rat LIMCH1 (119.5 kDa) and a truncated ALP variant, ΔLIM-ALP (51 kDa), and analyzed their secondary structures using circular dichroism spectroscopy. Our results indicate that both proteins differ markedly from known ureohydrolases, exhibiting a high proportion of disordered regions (~60%) and β-structures (~30%). In contrast, Escherichia coli agmatinase displays a well-defined α/β/α sandwich fold. Despite these structural differences, ALP/LIMCH1 remain the only known mammalian proteins exhibiting agmatinase activity. To gain insight into the putative active site of ALP, we proposed candidate Mn²⁺-binding residues and generated single-point mutants (N213A, Q215A, D217A, E288A, K290A). Although these mutations did not significantly alter Mn²⁺ binding or its overall content in the protein samples, four mutants exhibited a decreased K_m for agmatine and a reduced V_max when normalized to protein concentration. Full article

In order to investigate the impact of drought and saline–alkaline stress on the growth and metabolic components of wheat, as well as to identify advantageous components of wheat under saline–alkaline conditions, metabolomics analysis was conducted separately on wheat cultivated in saline–alkaline soil at Zhong Jie Industrial Park (AAW) and generally grown wheat at Xian Huanyuan Village (GW). The results revealed that AAW exhibited higher levels of accumulated metabolites compared to GW. Specifically, under drought and saline–alkaline stress, alkaloids, flavones, amino acids, and derivatives were significantly up-regulated, while phenolic acids and terpenoids were down-regulated. Notably, 29 differential metabolites, including vitexin-2″-O-glucoside, N-feruloyl agmatine, apigenin-8-C-glucoside, and L-alanyl-L-phenylalanine, showed significant differences between AAW and GW. Flavone and flavonol biosynthesis, apigenin C-glycosides biosynthesis, and metabolic pathways were identified as key pathways contributing to the observed differences in metabolite production. Apigenin-8-C-glucoside and vitexin-2″-O-glucoside emerged as reliable biomarkers for distinguishing between AAW and GW. These findings suggest that metabolites unique to wheat grown in saline–alkaline soil may serve as biomarkers for developing stress-resistant varieties, warranting further study of their functional components in food products. Full article

Background: Agmatine (AG) is an endogenous neurotransmitter discovered in 1910. It acts on imidazoline I1 and I2 receptors, alpha-2 adrenoceptors, N-methyl-D-aspartate receptors (NMDAR), and serotonergic receptors and modulates nitric oxide synthase (NOS) subtypes. It has neuroprotective, anxiolytic, antidepressant, anticonvulsant, and anti-inflammatory properties and is involved in cognitive functions and withdrawal. The cardiovascular effects of AG began to be explored after the hypotensive effect of clonidine, an imidazoline agonist, was demonstrated. The current study aimed to systematize the effects of AG on the cardiovascular system obtained in previous preclinical studies. Methods: We searched three databases, PubMed, Cochrane, and Embase, using the keywords “agmatine” and “cardiac” or “vascular.” Results: Sixty studies were eligible and included in the analysis. Initially identified as Clonidine Displacing Substance (CDS), AG has demonstrated dual effects—an increase or decrease in blood pressure or in heart rate. Conclusions: The effects exerted by AG depend on the dose and route of administration, as well as on the receptors involved and the pathophysiological pathway used. Full article

Polyamines (PAs), including putrescine, spermidine, spermine, and thermospermine, play essential roles in plant growth, development, and responses to stress. However, the structure and function of PA biosynthetic genes in pepper remain poorly characterized. This study aimed to identify PA biosynthesis genes in the pepper genome using bioinformatics approaches and to assess their expression under various stress conditions. A total of 16 PA biosynthesis-related genes were identified, representing members of the arginine decarboxylase (ADC), ornithine decarboxylase (ODC), agmatine iminohydrolase (AIH), N-carbamoylputrescine amidohydrolase (CPA), S-adenosylmethionine decarboxylase (SAMDC), spermidine synthase (SPDS), spermine synthase (SPMS), and ACAULIS5 (ACL5) gene families. These genes encode proteins with an average molecular weight of approximately 40 kDa, primarily localized in the mitochondria and cytoplasm. Promoter analysis revealed multiple cis-acting elements associated with stress and phytohormone responsiveness. Gene expression was induced by various abiotic stresses, including saline-alkaline, drought, heat, cold, and hydrogen peroxide, as well as by phytohormones such as abscisic acid, ethylene, salicylic acid, auxin, and gibberellin. Overall, this study provides a comprehensive analysis of PA biosynthesis genes in pepper and highlights their potential roles in stress adaptation and hormone signalling, offering a foundation for further exploration of PA-mediated stress tolerance mechanisms. Full article

Cognitive decline is a common complication of diabetes mellitus, driven in part by oxidative stress and impaired glucose–insulin homeostasis. This study examined the neuroprotective effects of agmatine (200 mg/kg intraperitoneally) in female BALB/c diabetic mice. Several receptor pathways were examined using commercially available antagonists. Behavioral performance was evaluated using the novel object recognition test. Metabolic parameters, such as glucose and insulin levels, as well as antioxidants, including catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH), were measured in blood and brain tissue. The diabetic mice exhibited impaired recognition memory (discrimination index = 0.08), hyperglycemia (24.3 mmol/L), decreased insulin levels (38.4 µU/mL), and diminished antioxidant defenses (CAT: 75.4 U/g tissue, SOD: 32.6 U/g tissue, and GSH: 8.3 mmol/g tissue). Agmatine treatment improved cognitive function and reversed the biochemical alterations. However, these effects were reduced when agmatine was co-administered with imidazoline I₂/I₃ receptor antagonists. Correlation analysis revealed that cognitive performance positively correlated with antioxidant enzyme levels and insulin levels and negatively correlated with glucose concentrations. Strong intercorrelations among CAT, SOD, and GSH levels suggest a coordinated antioxidant response. Overall, these results imply that agmatine’s neuroprotective effects are partially mediated by modulation of the oxidative balance and glucose–insulin regulation via imidazoline receptors. Full article

Background/Objectives: Chronic craniofacial inflammation is recognized as a factor in anxiety-like behaviors, yet effective therapeutic options remain limited. Agmatine, a dietary bioactive compound found in fermented foods such as sake lees, exhibits modulatory effects on neural functions, alleviating psychological distress like anxiety associated with local inflammation. Methods: We investigated both the therapeutic and preventive effects of agmatine on anxiety-like behaviors and the related neural basis in a mouse model of persistent craniofacial inflammation induced by complete Freund’s adjuvant (CFA). Results: Comprehensive behavioral assessments, including the elevated plus maze, open field, dark–light box, social interaction, and novel object recognition tests, revealed that therapeutic agmatine administration (1.0 and 30 mg/kg) significantly reduced CFA-induced anxiety-like behaviors, with the higher dose showing more robust and sustained effects across multiple time points. These behavioral improvements were paralleled by reductions in acetylated histone H3, FosB, and c-Fos expression in key anxiety-related brain regions, suggesting a reversal of craniofacial inflammation-associated neural changes. In contrast, preventive agmatine treatment exerted modest and time-dependent behavioral benefits with minimal molecular normalization. Notably, preventive agmatine did not affect general locomotor activity (indicated by total movement distance), indicating that its anxiolytic effects were not confounded by altered locomotor activity. Metabolomic analysis confirmed the presence of agmatine in sake lees (~0.37 mM), supporting the hypothesis that fermented food products might offer dietary routes to emotional resilience. Conclusions: These findings underscore agmatine’s promise as a context-specific epigenetic modulator capable of mitigating anxiety-like behaviors by normalizing inflammation-driven molecular dysregulation in the brain. Full article

Background/Objectives: Tacrolimus is an immunosuppressant drug widely used to prevent organ transplant rejection. Preclinical and clinical studies report that tacrolimus has destructive impacts on the male reproductive system owing to the induction of oxidative stress and inflammation. This study aimed at examining defensive impacts of agmatine against tacrolimus-induced testicular toxicity in rats. Methods: Male Wistar rats were randomly divided into six groups and treated based on the experimental design for 14 days. By the end of this study, blood samples were obtained to measure testosterone and luteinizing hormone. Also, both testes were removed for molecular analysis and histopathological examinations. Results: Agmatine administration increased serum levels of testosterone and luteinizing hormone and ameliorated all histopathological and toxicological changes induced by tacrolimus. Agmatine administration attenuated tacrolimus-induced oxidative stress as evidenced by the reduction of malondialdehyde content and inducible nitric oxide synthase expression and the elevation of reduced glutathione. This was parallel to the restoration of nuclear factor erythroid 2-related factor2 and hemeoxygenase-1 expression. Moreover, agmatine decreased the expressions of nuclear factor kappa B and interleukin-17. Agmatine also decreased the cell death revealed by decreased caspase-3 expression and increased expression of the antiapoptotic marker Bcl-2 in a dose-dependent manner. The antioxidant, anti-inflammatory, and antiapoptotic effects of agmatine were explained by increased expression of sirtuin-1. Conclusions: agmatine effectively attenuated testicular injuries induced by tacrolimus and enhanced spermatogenesis. This protective effect of agmatine might be mediated via the upregulation of sirtuin-1 expression that in turn restores oxidative status and regulates nuclear factor erythroid 2-related factor2/nuclear factor kappa B/Bcl-2 signaling. Full article

Agmatine is a naturally occurring biogenic amine that acts primarily as an inhibitor of neuronal nitric oxide synthase (nNOS). Previous studies have shown that both acute and chronic agmatine administration induced anxiolytic and antidepressant-like effects in rodents. In the dorsal raphe nucleus (DRN), nitric oxide (NO) donors inhibit serotonergic (5-HT) neuronal activity, with the nNOS-expressing 5-HT neurons showing lower baseline firing rates than the non-nNOS expressing neurons. Our study aimed to test the hypothesis that the psychoactive effects of agmatine are mediated, at least in part, via a mechanism involving the stimulation of the DRN 5-HT neurons, as well as to assess the molecular pathway allowing agmatine to modulate the excitability of 5-HT neurons. Using extracellular in vivo electrophysiology, we demonstrated that both acute (1–3 mg/kg, i.v.) and chronic (40 mg/kg/day, i.p., 14 days) agmatine administration significantly increased the firing rate of DRN 5-HT neurons. Quantitative PCR (qPCR) analysis revealed that chronic agmatine treatment selectively upregulated the expression of serotonin-1B (5-HT_1B) and serotonin-2A (5-HT_2A) receptor mRNA in the DRN. Previous studies have shown that DRN 5-HT_2A receptor activation stimulates 5-HT neurons and produces antidepressant-like effects; our findings suggest that agmatine’s excitatory effect on DRN 5-HT neurons may be partially 5-HT_2A receptor-dependent. Given that modulation of the 5-HT neuronal firing activity is critical for the proper antidepressant efficacy, nNOS inhibitors can be potential antidepressants by their own and/or effective adjuncts to other antidepressant drugs. Full article

Age-related macular degeneration (AMD) is an age-related disorder that is a global public health problem. The non-enzymatic Maillard reaction results in the formation of advanced glycation end products (AGEs). Accumulation of AGEs in drusen plays a key role in AMD. AGE-reducing drugs may contribute to the prevention and treatment of AGE-related disease. Fructosamine oxidase (FAOD) acts on fructosyl lysine and fructosyl valine. Based upon the published results of fructosamine 3-kinase (FN3K) and FAOD obtained in cataract and presbyopia, we studied ex vivo FAOD treatment as a non-invasive AMD therapy. On glycolaldehyde-treated porcine retinas, FAOD significantly reduced AGE autofluorescence (p = 0.001). FAOD treatment results in a breakdown of AGEs, as evidenced using UV fluorescence, near-infrared microspectroscopy on stained tissue sections of human retina, and gel permeation chromatography. Drusen are accumulations of AGEs that build up between Bruch’s membrane and the retinal pigment epithelium. On microscopy slides of human retina affected by AMD, a significant reduction in drusen surface to 45 ± 21% was observed following FAOD treatment. Enzymatic digestion followed by mass spectrometry of fructose- and glucose-based AGEs (produced in vitro) revealed a broader spectrum of substrates for FAOD, as compared to FN3K, including the following: fructosyllysine, carboxymethyllysine, carboxyethyllysine, and imidazolone. In contrast to FN3K digestion, agmatine (4-aminobutyl-guanidine) was formed following FAOD treatment in vitro. The present study highlights the therapeutic potential of FAOD in AMD by repairing glycation-induced damage. Full article

Polyamines are polycations derived from amino acids that play an important role in proliferation and growth in almost all living cells. In Streptococcus pneumoniae (the pneumococcus), modulation of polyamine metabolism not only plays an important regulatory role in central metabolism, but also impacts virulence factors such as the capsule and stress responses that affect survival in the host. However, functional annotation of enzymes from the polyamine biosynthesis pathways in the pneumococcus is based predominantly on computational prediction. In this study, we cloned SP_0166, predicted to be a pyridoxal-dependent decarboxylase, from the Orn/Lys/Arg family pathway in S. pneumoniae TIGR4 and expressed and purified the recombinant protein. We performed biochemical characterization of the recombinant SP_0166 and confirmed the substrate specificity. For polyamine analysis, we developed a simultaneous quantitative method using hydrophilic interaction liquid chromatography (HILIC)-based liquid chromatography–tandem mass spectrometry (LC–MS/MS) without derivatization. SP_0166 has apparent Km, kcat, and kcat/Km values of 11.3 mM, 715,053 min⁻¹, and 63,218 min⁻¹ mM⁻¹, respectively, with arginine as a substrate at pH 7.5. We carried out inhibition studies of SP_0166 enzymatic activity with arginine as a substrate using chemical inhibitors DFMO and DFMA. DFMO is an irreversible inhibitor of ornithine decarboxylase activity, while DFMA inhibits arginine decarboxylase activity. Our findings confirm that SP_0166 is inhibited by DFMA and DFMO, impacting agmatine production. The use of arginine as a substrate revealed that the synthesis of putrescine by agmatinase and N-carbamoylputrescine by agmatine deiminase were both affected and inhibited by DFMA. This study provides experimental validation that SP_0166 is an arginine decarboxylase in pneumococci. Full article