Active and inhibited human catalase structures: ligand and NADPH binding and catalytic mechanism

Enzymes in Addressing Hypoxia for Biomaterials Engineering

Oxygen is essential for normal cellular functions. Hypoxia impacts various cellular processes, such as metabolism, growth, proliferation, angiogenesis, metastasis, tumorigenesis, microbial infection, and immune response, mediated by hypoxia-inducible factors (HIFs). Hypoxia contributes to the progression and development of cancer, cardiovascular diseases, metabolic disorders, kidney diseases, and infections. The potential alleviation of hypoxia has been explored through the enzymatic in situ decomposition of hydrogen peroxide, leading to the generation of oxygen. However, challenges such as limited stability restrict the effectiveness of enzymes such as catalase in biomedical and in vivo applications. To overcome these limitations, targeted delivery of the enzymes has been proposed. This review offers a critical comparison of i) current approaches to enhance the in vivo stability of catalase; and ii) the structure, mechanism of action, and kinetics of catalase and catalase-like nanozymes.

Why cells need iron: a compendium of iron utilisation

Iron deficiency is globally prevalent, causing an array of developmental, haematological, immunological, neurological, and cardiometabolic impairments, and is associated with symptoms ranging from chronic fatigue to hair loss. Within cells, iron is utilised in a variety of ways by hundreds of different proteins. Here, we review links between molecular activities regulated by iron and the pathophysiological effects of iron deficiency. We identify specific enzyme groups, biochemical pathways, cellular functions, and cell lineages that are particularly iron dependent. We provide examples of how iron deprivation influences multiple key systems and tissues, including immunity, hormone synthesis, and cholesterol metabolism. We propose that greater mechanistic understanding of how cellular iron influences physiological processes may lead to new therapeutic opportunities across a range of diseases.

Electron transfer in biological systems

Examples of how metalloproteins feature in electron transfer processes in biological systems are reviewed. Attention is focused on the electron transport chains of cellular respiration and photosynthesis, and on metalloproteins that directly couple electron transfer to a chemical reaction. Brief mention is also made of extracellular electron transport. While covering highlights of the recent and the current literature, this review is aimed primarily at introducing the senior undergraduate and the novice postgraduate student to this important aspect of bioinorganic chemistry.

Modulation of antioxidant enzyme by light and heavy rare earth metals: A case study with catalase

The present study highlights the hazardous effect of heavy and light rare earth elements (REEs) on bovine liver catalase (BLC) using a combination of spectroscopic and computational methods. The presence of Praseodymium chloride (PrCl3) and Gadolinium chloride (GdCl3) resulted in a substantial reduction in catalytic efficiency of BLC by approximately 1.8 and 2.6 fold, respectively. The compromised activity was further accompanied by conformational rearrangements at the secondary and tertiary levels as evidenced by circular dichroism (CD) and fluorescence spectroscopy. These analyses revealed a significant decrease in α-helical content and a simultaneous increase in random coils, disrupting intramolecular hydrogen bonding. Furthermore, the zeta potential (ζ) of BLC demonstrated a reversal from negative to positive ζ values upon the addition of PrCl3 and GdCl3, indicating BLC-lanthanide complex formation. Isothermal titration calorimetry (ITC) supports spontaneous interaction with negative free energy favouring endothermic reaction. This was further supported by docking studies which revealed the binding of PrCl3 and GdCl3 within the active site of BLC thus interfering with the catalytic ability to degrade hydrogen peroxide (H2O2). Nevertheless, a significant decline in the melting temperature (Tm) of BLC was observed in the presence of lanthanides suggesting the thermal instability of the enzyme. Thus, a similar approach could be applied to evaluate the hazardous effects of lanthanides on structural and functional changes in other proteins or similar biomolecules.

The biochemistry of the carcinogenic alcohol metabolite acetaldehyde

Acetaldehyde (AcH) is the first metabolite of ethanol and is proposed to be responsible for the genotoxic effects of alcohol consumption. As an electrophilic aldehyde, AcH can form multiple adducts with DNA and other biomolecules, leading to function-altering and potentially toxic and carcinogenic effects. In this review, we describe sources of AcH in humans, including AcH biosynthesis mechanisms, and outline the structures, properties and functions of AcH-derived adducts with biomolecules. We also describe human AcH detoxification mechanisms and discuss ongoing challenges in the field.

Targeting catalase in cancer

Healthy cells have developed a sophisticated network of antioxidant molecules to prevent the toxic accumulation of reactive oxygen species (ROS) generated by diverse environmental stresses. On the opposite, cancer cells often exhibit high levels of ROS and an altered levels of antioxidant molecules compared to normal cells. Among them, the antioxidant enzyme catalase plays an essential role in cell defense against oxidative stress through the dismutation of hydrogen peroxide into water and molecular oxygen, and its expression is often decreased in cancer cells. The elevation of ROS in cancer cells provides them proliferative advantages, and leads to metabolic reprogramming, immune escape and metastasis. In this context, catalase is of critical importance to control these cellular processes in cancer through various mechanisms. In this review, we will discuss the major progresses and challenges in understanding the role of catalase in cancer for this last decade. This review also aims to provide important updates regarding the regulation of catalase expression, subcellular localization and discuss about the potential role of microbial catalases in tumor environment. Finally, we will describe the different catalase-based therapies and address the advantages, disadvantages, and limitations associated with modulating catalase therapeutically in cancer treatment.

DNA interaction of selected tetrahydropyrimidine and its effects against CCl4-induced hepatotoxicity in vivo: Part II

Tetrahydropyrimidine (compound A = methyl 4-[4'-(heptyloxy)-3'-methoxyphenyl]-1,6-dimethyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate) was chosen for in vivo studies after exhibiting noteworthy in vitro activity against the K562 and MDA-MB-231 cell lines, with IC50 values of 9.20 ± 0.14 µM and 12.76 ± 1.93 µM, respectively. According to experimental (fluorescence titration, viscosity, and differential scanning calorimetry) results, A interacts with DNA via the minor groove. In vivo, acute oral toxicity studies in Wistar albino rats proved no noticeable symptoms of either toxicity or death during the follow-up period. Genotoxic and antigenotoxic studies at three different concentrations of A (5, 10, and 20 mg/kg of body weight) in Wistar albino rats showed that the dose of 5 mg/kg body weight did not cause DNA damage and had a remarkable DNA protective activity against CCl4-induced DNA damage, with a percentage reduction of 78.7%. It is also important to note that, under the investigated concentrations of A, liver damage is not observed. Considering all experimental outcomes realized under various in vivo investigations (acute oral toxicity, genotoxicity, antigenotoxicity, and biochemical tests), compound A could be a promising candidate for further clinical testing.

Ecofriendly approaches to efficiently enhance catalase performance

The present work reports on two approaches to enhance catalase (CAT) activity and its stability by using two simple, green processes. In the first procedure, CAT was transiently exposed to an ionic liquid (IL) in the presence of redox molecules related to CAT structure which resulted in partial denaturation. The other method, which uses high hydraulic pressure (HHP) to partially denature CAT (in the presence of redox molecules), has the advantage of being completely reagentless. In both cases, partial denaturation was followed by dialysis, hence refolding and entrapment of redox molecules within the modified 3-D CAT structure (affording a "wired" enzyme). The two approaches to enzyme "wiring" are discussed comparatively from the point of view of the parameters used during the procedure, residual enzyme activity, nature of the modifier, interaction between CAT and the redox molecules, antioxidant activity, and stability over time of the modified protein. Samples of CAT modified in the presence of iron sulfate heptahydrate from each series, respectively, were used to make enzyme electrodes which were tested as amperometric biosensors for hydrogen peroxide detection. Both showed catalytic effect and linear behavior and have potential for applications in the food industry, pharmaceuticals and the textile industry.

Chrysomycin A Reshapes Metabolism and Increases Oxidative Stress to Hinder Glioblastoma Progression

Glioblastoma represents the predominant and a highly aggressive primary neoplasm of the central nervous system that has an abnormal metabolism. Our previous study showed that chrysomycin A (Chr-A) curbed glioblastoma progression in vitro and in vivo. However, whether Chr-A could inhibit orthotopic glioblastoma and how it reshapes metabolism are still unclear. In this study, Chr-A markedly suppressed the development of intracranial U87 gliomas. The results from airflow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) indicated that Chr-A improved the abnormal metabolism of mice with glioblastoma. Key enzymes including glutaminase (GLS), glutamate dehydrogenases 1 (GDH1), hexokinase 2 (HK2) and glucose-6-phosphate dehydrogenase (G6PD) were regulated by Chr-A. Chr-A further altered the level of nicotinamide adenine dinucleotide phosphate (NADPH), thus causing oxidative stress with the downregulation of Nrf-2 to inhibit glioblastoma. Our study offers a novel perspective for comprehending the anti-glioma mechanism of Chr-A, highlighting its potential as a promising chemotherapeutic agent for glioblastoma.

Characterization and molecular docking of tetrapeptides with cellular antioxidant and ACE inhibitory properties from cricket (Acheta domesticus) protein hydrolysate

Wide-ranging bioactivities of enzymatically digested insect protein to produce peptides have been targeted for functional food development. In this study, fractionated peptides obtained from cricket (Acheta domesticus) protein hydrolysate by alcalase digestion were identified and evaluated for their bioactivities. Peptide fractions F44, F45, and F46, isolated through size exclusion chromatography, demonstrated strong cytoprotective effects on SH-SY5Y and HepG2 cells exposed to H2O2. This was evidenced by a 2-fold decrease in reactive oxygen species (ROS) accumulation in the cells and a 3-fold upregulation of genes encoding antioxidant enzymes. The F45 peptide fractions also showed chemical antioxidant activities ranging from approximately 290 to 393 mg trolox/g peptide, measured by DPPH, ABTS, and FRAP assays. Furthermore, F45 demonstrated the highest angiotensin-converting enzyme I (ACE) inhibitory activity, 57.93 %. F45 induced higher levels of Nrf2, SOD1, SOD2, CAT, GSR, and GPx4 gene expression in SH-SY5Y and HepG2 cells compared to cells treated with H2O2 and no peptides (p < 0.05). Cells treated with H2O2 and F45 exhibited significantly increased antioxidant enzyme activity, including SOD, CAT, GSR, and GPx (p < 0.05). The F45B fraction from F45 was sequenced to obtain FVEG and FYDQ tetrapeptides. Molecular docking analysis revealed their high binding affinity to cellular antioxidant enzymes (SOD, CAT, GSR, GPx1, and GPx4), an antioxidant-related protein (Keap1), and ACE. These results suggest that the novel tetrapeptides from Acheta domesticus demonstrate important biological activities, establishing them as significant cellular antioxidant activities and a potential source of antihypertensive peptides.

Elucidation and active ingredient identification of aqueous extract of Ficus exasperata Vahl leaf against bisphenol A-induced toxicity through in vivo and in silico assessments

Bisphenol A (BPA), an endocrine-disrupting chemical, poses significant health problems due to its induction of oxidative stress, inflammation, etc. Whereas Ficus exasperata Vahl leaf (FEVL) was reported for its ethnopharmacological properties against several ailments owing to its antioxidant, anti-inflammatory properties, etc. Here, we aim to elucidate and identify the bioactive compounds of aqueous extract of FEVL (AEFEVL) against BPA-induced toxicity using in vivo and in silico assessments. To determine the BPA toxicity mechanism and safe doses of AEFEVL, graded doses of BPA (0-400 μM) and AEFEVL (0-2.0 mg/10 g diets) were separately fed to flies to evaluate survival rates and specific biochemical markers. The mitigating effect of AEFEVL (0.5 and 1.0 mg/10 g diet) against BPA (100 and 200 μM)-induced toxicity in the flies after 7-day exposure was also carried out. Additionally, molecular docking analysis of BPA and BPA-o-quinone (BPAQ) against selected antioxidant targets, and HPLC-MS-revealed AEFEVL compounds against Keap-1 and IKKβ targets, followed by ADMET analysis, was conducted. Emergence rate, climbing ability, acetylcholinesterase, monoamine oxidase-B, and glutathione-S-transferase activities, and levels of total thiols, non-protein thiols, nitric oxide, protein carbonyl, malondialdehyde, and cell viability were evaluated. BPA-induced altered biochemical and behavioral parameters were significantly mitigated by AEFEVL in the flies (p < 0.05). BPAQ followed by BPA exhibited higher inhibitory activity, and epigallocatechin (EGC) showed the highest inhibitory activity among the AEFEVL compounds with desirable ADMET properties. Conclusively, our findings revealed that EGC might be responsible for the mitigative effect displayed by AEFEVL in BPA-induced toxicity in D. melanogaster.

Graphical abstract

A remarkable peroxidase-like behavior of the catalase KatA from the pathogenic bacteria Helicobacter pylori: The oxidation reaction with formate as substrate and the stabilization of an [Fe(IV) = O Trp•] intermediate assessed by multifrequency EPR spectroscopy

We have characterized the catalytic cycle of the Helicobacter pylori KatA catalase (HPC). H. pylori is a human and animal pathogen responsible for gastrointestinal infections. Multifrequency (9-285 GHz) EPR spectroscopy was applied to identify the high-valent intermediates (5 ≤ pH ≤ 8.5). The broad (2000 G) 9-GHz EPR spectrum consistent with the [Fe(IV) = O Por•+] intermediate was detected, and showed a clear pH dependence on the exchange-coupling of the radical (delocalized over the porphyrin moiety) due to the magnetic interaction with the ferryl iron. In addition, Trp• (for pH ≤ 6) and Tyr• (for 5 ≤ pH ≤ 8.5) species were distinguished by the advantageous resolution of their g-values in the 285-GHz EPR spectrum. The unequivocal identification of the high-valent intermediates in HPC by their distinct EPR spectra allowed us to address their reactivity towards substrates. The stabilization of an [Fe(IV) = O Trp•] species in HPC, unprecedented in monofunctional catalases and possibly involved in the oxidation of formate to the formyloxyl radical at pH ≤ 6, is reminiscent of intermediates previously identified in the catalytic cycle of bifunctional catalase-peroxidases. The 2e- oxidation of formate by the [Fe(IV) = O Por•+] species, both at basic and acidic pH conditions, involving a 1H+/2e- oxidation in a cytochrome P450 peroxygenase-like reaction is proposed. Our findings demonstrate that moonlighting by the H. pylori catalase includes formate oxidation, an enzymatic reaction possibly related to the unique strategy of the neutrophile bacterium for gastric colonization, that is the release of CO2 to regulate the pH in the acidic environment.

Pepper catalase: a broad analysis of its modulation during fruit ripening and by nitric oxide

Catalase is a major antioxidant enzyme located in plant peroxisomes that catalyzes the decomposition of H2O2. Based on our previous transcriptomic (RNA-Seq) and proteomic (iTRAQ) data at different stages of pepper (Capsicum annuum L.) fruit ripening and after exposure to nitric oxide (NO) enriched atmosphere, a broad analysis has allowed us to characterize the functioning of this enzyme. Three genes were identified, and their expression was differentially modulated during ripening and by NO gas treatment. A dissimilar behavior was observed in the protein expression of the encoded protein catalases (CaCat1-CaCat3). Total catalase activity was down-regulated by 50% in ripe (red) fruits concerning immature green fruits. This was corroborated by non-denaturing polyacrylamide gel electrophoresis, where only a single catalase isozyme was identified. In vitro analyses of the recombinant CaCat3 protein exposed to peroxynitrite (ONOO-) confirmed, by immunoblot assay, that catalase underwent a nitration process. Mass spectrometric analysis identified that Tyr348 and Tyr360 were nitrated by ONOO-, occurring near the active center of catalase. The data indicate the complex regulation at gene and protein levels of catalase during the ripening of pepper fruits, with activity significantly down-regulated in ripe fruits. Nitration seems to play a key role in this down-regulation, favoring an increase in H2O2 content during ripening. This pattern can be reversed by the exogenous NO application. While plant catalases are generally reported to be tetrameric, the analysis of the protein structure supports that pepper catalase has a favored quaternary homodimer nature. Taken together, data show that pepper catalase is down-regulated during fruit ripening, becoming a target of tyrosine nitration, which provokes its inhibition.

Unveiling the Detrimental Effect of Glipizide on Structure and Function of Catalase: Spectroscopic, Thermodynamics and Simulation Studies

Free radicals, products of oxidative processes, induce cellular damage linked to diseases like Parkinson's and diabetes due to increased reactive oxygen species (ROS) levels. Catalase, crucial for scavenging ROS, emerges as a therapeutic agent against ailments including atherosclerosis and tumor progression. Its primary function involves breaking down hydrogen peroxide into water and oxygen. Research on catalase-drug interactions reveals structural changes under specific conditions, affecting its activity and cellular antioxidant balance, highlighting its pivotal role in defending against oxidative stress-related diseases. Hence, targeting catalase is considered an effective strategy for controlling ROS-induced cellular damage. This study investigates the interaction between bovine liver catalase and glipizide using spectroscopic and computational methods. It also explores glipizide's effect on catalase activity. More than 20% inhibition of catalase enzymatic activity was recorded in the presence of 50 µM glipizide. To investigate the inhibition of catalase activity by glipizide, we performed a series of binding studies. Glipizide was found to form a complex with catalase with moderate affinity and binding constant in the range of 3.822 to 5.063 × 104 M-1. The binding was spontaneous and entropically favourable. The α-helical content of catalase increased from 24.04 to 29.53% upon glipizide complexation. Glipizide binding does not alter the local environment surrounding the tyrosine residues while a notable decrease in polarity around the tryptophan residues of catalase was recorded. Glipizide interacted with numerous active site residues of catalase including His361, Tyr357, Ala332, Asn147, Arg71, and Thr360. Molecular simulations revealed that the catalase-glipizide complex remained relatively stable in an aqueous environment. The binding of glipizide had a negligible effect on the secondary structure of catalase, and hydrogen bonds persisted consistently throughout the trajectory. These results could aid in the development of glipizide as a potent catalase inhibitor, potentially reducing the impact of reactive oxygen species (ROS) in the human body.

Advances in metal-organic framework-based nanozymes in ROS scavenging medicine

Reactive oxygen species (ROS) play important roles in regulating various physiological functions in the human body, however, excessive ROS can cause serious damage to the human body, considering the various limitations of natural enzymes as scavengers of ROS in the body, the development of better materials for the scavenging of ROS is of great significance to the biomedical field, and nanozymes, as a kind of nanomaterials which can show the activity of natural enzymes. Have a good potential for the development in the area of ROS scavenging. Metal-organic frameworks (MOFs), which are porous crystalline materials with a periodic network structure composed of metal nodes and organic ligands, have been developed with a variety of active nanozymes including catalase-like, superoxide dismutase-like, and glutathione peroxidase-like enzymes due to the adjustability of active sites, structural diversity, excellent biocompatibility, and they have shown a wide range of applications and prospects. In the present review, we first introduce three representative natural enzymes for ROS scavenging in the human body, methods for the detection of relevant enzyme-like activities and mechanisms of enzyme-like clearance are discussed, meanwhile, we systematically summarize the progress of the research on MOF-based nanozymes, including the design strategy, mechanism of action, and medical application, etc. Finally, the current challenges of MOF-based nanozymes are summarized, and the future development direction is anticipated. We hope that this review can contribute to the research of MOF-based nanozymes in the medical field related to the scavenging of ROS.

Exploring Therapeutic Potential of Catalase: Strategies in Disease Prevention and Management

The antioxidant defense mechanisms play a critical role in mitigating the deleterious effects of reactive oxygen species (ROS). Catalase stands out as a paramount enzymatic antioxidant. It efficiently catalyzes the decomposition of hydrogen peroxide (H2O2) into water and oxygen, a potentially harmful byproduct of cellular metabolism. This reaction detoxifies H2O2 and prevents oxidative damage. Catalase has been extensively studied as a therapeutic antioxidant. Its applications range from direct supplementation in conditions characterized by oxidative stress to gene therapy approaches to enhance endogenous catalase activity. The enzyme's stability, bioavailability, and the specificity of its delivery to target tissues are significant hurdles. Furthermore, studies employing conventional catalase formulations often face issues related to enzyme purity, activity, and longevity in the biological milieu. Addressing these challenges necessitates rigorous scientific inquiry and well-designed clinical trials. Such trials must be underpinned by sound experimental designs, incorporating advanced catalase formulations or novel delivery systems that can overcome existing limitations. Enhancing catalase's stability, specificity, and longevity in vivo could unlock its full therapeutic potential. It is necessary to understand the role of catalase in disease-specific contexts, paving the way for precision antioxidant therapy that could significantly impact the treatment of diseases associated with oxidative stress.

Centella asiatica improves memory and executive function in middle-aged rats by controlling oxidative stress and cholinergic transmission

ETHNOPHARMACOLOGICAL RELEVANCE

Centella asiatica (L.) Urban, is a medicinal herb with rich history of traditional use in Indian subcontinent. This herb has been valued for its diverse range of medicinal properties including memory booster, and also as a folk treatment for skin diseases, wound healing and mild diuretic.

AIM OF STUDY

Aging is a gradual and continuous process of natural decay in the biological systems, including the brain. This work aims to evaluate the effectiveness of ethanolic extract of Centella asiatica (CAE) on age-associated cognitive impairments in rats, as well as the underlying mechanism.

MATERIAL AND METHODS

Rats were allocated into five distinct groups of 5 animals each: Young rats (3 months old rats), middle-aged (m-aged) rats (13-14 months old), and the remaining three groups were comprised of m-aged rats treated with different concentrations of CAE, viz., 150, 300, and 450 mg/kg b. w., orally for 42 days. Y-maze, open field, novel object recognition, and elevated plus maze tests were used to assess animal behavior. The malondialdehyde (MDA), superoxide dismutase (SOD), and acetylcholinesterase (AChE) assays; and H&E staining were done in the rat brain to assess the biochemical and structural changes. CAE was also subjected to HPLC analysis, in vitro antioxidant and anti-cholinergic activity. The active compounds of CAE were docked with AChE and BuChE in molecular docking study.

RESULTS

The results showed that CAE treatment improves behavioral performance; attenuates the age-associated increase in MDA content, SOD, and AChE activity; and reduces neuronal loss. In vitro study showed that CAE has concentration-dependent antioxidant and anti-AChE activity. Furthermore, the presence of Asiatic acid and Madecassic acid in CAE and their good binding with cholinergic enzymes (in silico) also suggest the anticholinergic effect of CAE.

CONCLUSION

The findings of the current study show that the anticholinergic and antioxidant effects of CAE are attributable to the presence of Asiatic acid and Madecassic acid, which not only provide neuroprotection against age-associated cognitive decline but also reverse it.

Aging effects of titanium dioxide on Cu toxicity to Daphnia magna: Exploring molecular docking and significance of surface properties

Cosmetics and personal care products containing titanium dioxide nanoparticles (TiO2 NPs) may enter aquatic environments, where the surface coatings of TiO2 NPs may change with aging due to environmental factors such as light, and potentially affect their bioaccumulation and toxicity. This study examined how aging impacted the physicochemical properties of three commercially available TiO2 NPs and subsequent influence on the bioaccumulation and toxicity of copper (Cu) in Daphnia magna (D. magna). We demonstrated that aging significantly affected the hydrophobicity of TiO2 NPs, which affected their binding to water molecules and adsorption of Cu. Changes of bioaccumulation of TiO2 NPs and Cu in D. magna ultimately affected the activities of intracellular antioxidant enzymes such as SOD, CAT, GSH-Px, and the transmembrane protein Na+/K+-ATPase. Molecular docking calculations demonstrated that changes of activities of these biological enzymes were due to the interaction between TiO2 NPs, Cu, and amino acid residues near the sites with the lowest binding energy and active center of the enzyme. Such effect was closely related to the hydrophobicity of TiO2 NPs. Our study demonstrated the close relationship between surface properties of TiO2 NPs and their biological effects, providing important evidence for understanding the behavior of nanomaterials in aquatic environments.

Changes in ATPase activity, antioxidant enzymes and proline biosynthesis in yeast Candida guilliermondii NP-4 under X-irradiation

This study investigates the effects of X-radiation on ATPase activity and antioxidant enzyme activity, particularly enzymes involved in proline biosynthesis, in yeast C. guilliermondii NP-4. Moreover, the study examined the post-irradiation repair processes in these cells. Results showed that X-irradiation at a dose of 300 Gy led to an increase in catalase (CAT) and superoxide dismutase (SOD) activity, as well as, an increase in the CAT/SOD ratio in C. guilliermondii NP-4. The repair of radiation-induced damage requires a substantial amount of energy, resulting in an increased demand for ATP in the irradiated and repaired yeasts. Consequently, the total and FoF1-ATPase activity in yeast homogenates and mitochondria increased after X-irradiation and post-irradiation repair. It was showed an increase in the activity of proline biosynthesis enzymes (ornithine transaminase and proline-5-carboxylate reductase) in X-irradiated C. guilliermondii NP-4, which remained elevated even after post-irradiation repair. As a result, the proline levels in X-irradiated and repaired yeasts were higher than those in non-irradiated cells. These findings suggest that proline may have a radioprotective effect on X-irradiated C. guilliermondii NP-4 yeasts. Taken together this study provides insights into the effects of X-radiation on ATPase activity, antioxidant enzyme activity, and proline biosynthesis in C. guilliermondii NP-4 yeast cells, highlighting the potential radioprotective properties of proline in X-irradiated yeasts.

Protective effects of esculetin against doxorubicin-induced toxicity correlated with oxidative stress in rat liver: In vivo and in silico studies

Doxorubicin (DOX) is widely used in cancer treatment but the dose-related toxicity of DOX on organs including the liver limit its use. Therefore, there is great interest in combining DOX with natural compounds with antioxidant properties to reduce toxicity and increase drug efficacy. Esculetin is a natural coumarin derivative with biological properties encompassing anti-inflammatory and antioxidant activities. In light of these properties, this study was meticulously crafted to investigate the potential of esculetin in preventing doxorubicin (DOX)-induced hepatotoxicity in Sprague-Dawley rats. The rats were divided into a total of six groups: control group, DOX group (administered DOX at a cumulative dose of 5 mg/kg intraperitoneally every other day for 2 weeks), E50 group (administered 50 mg/kg of esculetin intraperitoneally every day), E100 group (administered 100 mg/kg of esculetin intraperitoneally every day) and combined groups (DOX + E50 and DOX + E100) in which esculetin was administered together with DOX. The treatments, both with DOX alone and in combination with E50, manifested a reduction in catalase (CAT mRNA) levels in comparison to the control group. Notably, the enzymatic activities of superoxide dismutase (SOD), CAT, and glutathione peroxidase (GPx) witnessed significant decreases in the liver of rats treated with DOX. Moreover, DOX treatment induced a statistically significant elevation in malondialdehyde (MDA) levels, coupled with a concurrent decrease in glutathione (GSH) levels. Additionally, molecular docking studies were conducted. However, further studies are needed to confirm the hepatoprotective properties of esculetin and to precisely elucidate its mechanisms of action.

DNA polyhedrons cube, prism, and square pyramid protect the catalytic activity of catalase: A thermodynamics and kinetics study

DNA is widely used as building block material for the construction of polyhedral nanostructures. DNA polyhedrons (DNA prism, cube, and square pyramid) are small 3D wireframed nanostructures with tunable shapes and sizes. Despite substantial progress in synthesis, the study regarding cellular responses to DNA polyhedrons is limited. Herein, the molecular interaction between DNA polyhedrons and the antioxidant enzyme, catalase has been explored. The enzymatic activity of bovine liver catalase (BLC) remains unaltered in the presence of DNA polyhedrons after 1 h of incubation. However, the activity of BLC was protected after 24 h of incubation in the presence of DNA polyhedrons as compared to the natural unfolding. The kinetics study confirmed the protective role of DNA polyhedrons on BLC with lower KM and higher catalytic efficiency. Furthermore, no profound conformational changes of BLC occur in the presence of DNA polyhedrons as observed in spectroscopic studies. From fluorescence quenching data we confirmed the binding between DNA polyhedrons and BLC. The thermodynamic parameters indicate that non-covalent bonds played a major role during the interaction of BLC with DNA polyhedrons. Moreover, the hepatic catalase activity remains unaltered in the presence of DNA polyhedrons. The cytotoxicity assay revealed that DNA polyhedrons were biocompatible in the cellular environment. The protective role of DNA polyhedrons on enzyme activity and the unaltered conformational change of protein ensures the biocompatibility of DNA polyhedrons in the cellular environment.

Sodium p-perfluorous nonenoxybenzene sulfonate induces ROS-mediated necroptosis by directly targeting catalase in HepG2 cells

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has been widely used as a substitute for perfluorooctane sulfonic acid (PFOS) because of its high surface activity and low cost, but the knowledge of its biological effects is still limited. In this study, we compared the toxic effects of OBS and PFOS on human hepatoma cells (HepG2). OBS resulted in lower cell viability, higher ROS levels, and more severe necrosis than PFOS, indicating that OBS caused higher cytotoxicity than PFOS. In this process, OBS induced a burst of ROS and downregulation of catalase (CAT). OBS-induced oxidative stress was recovered after the CAT overexpression, but the CAT levels were not reversed after N-acetylcysteine (NAC) pretreatment. This indicates that the downregulated CAT is an upstream signal of the ROS burst. Moreover, drug affinity targeting assay, spectroscopic analysis and molecular docking were conducted, showing that OBS directly targeted CAT and therefore downregulated CAT. In addition, we found that OBS-induced necrosis is RIP1/RIP3-dependent programmed necroptosis. In summary, OBS directly targets CAT to reduce CAT levels and induces oxidative stress and necroptosis. Our findings are helpful to understand the toxicity of OBS and to evaluate the safety of OBS as a substitute for PFOS.

Investigation of how gate residues in the main channel affect the catalytic activity of Scytalidium thermophilum catalase

Catalase is an antioxidant enzyme that breaks down hydrogen peroxide (H2O2) into molecular oxygen and water. In all monofunctional catalases the pathway that H2O2 takes to the catalytic centre is via the `main channel'. However, the structure of this channel differs in large-subunit and small-subunit catalases. In large-subunit catalases the channel is 15 Å longer and consists of two distinct parts, including a hydrophobic lower region near the heme and a hydrophilic upper region where multiple H2O2 routes are possible. Conserved glutamic acid and threonine residues are located near the intersection of these two regions. Mutations of these two residues in the Scytalidium thermophilum catalase had no significant effect on catalase activity. However, the secondary phenol oxidase activity was markedly altered, with kcat and kcat/Km values that were significantly increased in the five variants E484A, E484I, T188D, T188I and T188F. These variants also showed a lower affinity for inhibitors of oxidase activity than the wild-type enzyme and a higher affinity for phenolic substrates. Oxidation of heme b to heme d did not occur in most of the studied variants. Structural changes in solvent-chain integrity and channel architecture were also observed. In summary, modification of the main-channel gate glutamic acid and threonine residues has a greater influence on the secondary activity of the catalase enzyme, and the oxidation of heme b to heme d is predominantly inhibited by their conversion to aliphatic and aromatic residues.

Senescence-associated 13-HODE production promotes age-related liver steatosis by directly inhibiting catalase activity

Aging is a major risk factor for metabolic disorders. Polyunsaturated fatty acid-derived bioactive lipids play critical roles as signaling molecules in metabolic processes. Nonetheless, their effects on age-related liver steatosis remain unknown. Here we show that senescent liver cells induce liver steatosis in a paracrine manner. Linoleic acid-derived 9-hydroxy-octadecadienoic acid (9-HODE) and 13-HODE increase in middle-aged (12-month-old) and aged (20-month-old) male mouse livers and conditioned medium from senescent hepatocytes and macrophages. Arachidonate 15-lipoxygenase, an enzyme for 13-HODE and 9-HODE production, is upregulated in senescent cells. A 9-HODE and 13-HODE mixture induces liver steatosis and activates SREBP1. Furthermore, catalase (CAT) is a direct target of 13-HODE, and its activity is decreased by 13-HODE. CAT overexpression reduces 13-HODE-induced liver steatosis and protects male mice against age-related liver steatosis. Therefore, 13-HODE produced by senescent hepatocytes and macrophages activates SREBP1 by directly inhibiting CAT activity and promotes liver steatosis.

Catalase from the Antarctic Fungus Aspergillus fumigatus I-9-Biosynthesis and Gene Characterization

Extremely cold habitats are a serious challenge for the existing there organisms. Inhabitants of these conditions are mostly microorganisms and lower mycetae. The mechanisms of microbial adaptation to extreme conditions are still unclear. Low temperatures cause significant physiological and biochemical changes in cells. Recently, there has been increasing interest in the relationship between low-temperature exposure and oxidative stress events, as well as the importance of antioxidant enzymes for survival in such conditions. The catalase is involved in the first line of the cells' antioxidant defense. Published information supports the concept of a key role for catalase in antioxidant defense against cold stress in a wide range of organisms isolated from the Antarctic. Data on representatives of microscopic fungi, however, are rarely found. There is scarce information on the characterization of catalase synthesized by adapted to cold stress organisms. Overall, this study aimed to observe the role of catalase in the survival strategy of filamentous fungi in extremely cold habitats and to identify the gene encoded catalase enzyme. Our results clearly showed that catalase is the main part of antioxidant enzyme defense in fungal cells against oxidative stress caused by low temperature exposure.

High-Resolution Structural Proteomics of Mitochondria Using the 'Build and Retrieve' Methodology

The application of integrated systems biology to the field of structural biology is a promising new direction, although it is still in the infant stages of development. Here we report the use of single particle cryo-EM to identify multiple proteins from three enriched heterogeneous fractions prepared from human liver mitochondrial lysate. We simultaneously identify and solve high-resolution structures of nine essential mitochondrial enzymes with key metabolic functions, including fatty acid catabolism, reactive oxidative species clearance, and amino acid metabolism. Our methodology also identified multiple distinct members of the acyl-CoA dehydrogenase family. This work highlights the potential of cryo-EM to explore tissue proteomics at the atomic level.

Gossypin mitigates oxidative damage by downregulating the molecular signaling pathway in oleic acid-induced acute lung injury

One of the leading causes of acute lung injury, which is linked to a high death rate, is pulmonary fat embolism. Increases in proinflammatory cytokines and the production of free radicals are related to the pathophysiology of acute lung injury. Antioxidants that scavenge free radicals play a protective role against acute lung injury. Gossypin has been proven to have antioxidant, antimicrobial, and anti-inflammatory properties. In this study, we compared the role of Gossypin with the therapeutically used drug Dexamethasone in the acute lung injury model caused by oleic acid in rats. Thirty rats were divided into five groups; Sham, Oleic acid model, Oleic acid+Dexamethasone (0.1 mg/kg), Oleic acid+Gossypin (10 and 20 mg/kg). Two hours after pretreatment with Dexamethasone or Gossypin, the acute lung injury model was created by injecting 1 g/kg oleic acid into the femoral vein. Three hours following the oleic acid injection, rats were decapitated. Lung tissues were extracted for histological, immunohistochemical, biochemical, PCR, and SEM imaging assessment. The oleic acid injection caused an increase in lipid peroxidation and catalase activity, pathological changes in lung tissue, decreased superoxide dismutase activity, and glutathione level, and increased TNF-α, IL-1β, IL-6, and IL-8 expression. However, these changes were attenuated after treatment with Gossypin and Dexamethasone. By reducing the expression of proinflammatory cytokines and attenuating oxidative stress, Gossypin pretreatment provides a new target that is equally effective as dexamethasone in the treatment of oleic acid-induced acute lung injury.

Single-atom catalysts-based catalytic ROS clearance for efficient psoriasis treatment and relapse prevention via restoring ESR1

Psoriasis is a common inflammatory disease of especially high recurrence rate (90%) which is suffered by approximately 3% of the world population. The overexpression of reactive oxygen species (ROS) plays a critical role in psoriasis progress. Here we show that biomimetic iron single-atom catalysts (FeN4O2-SACs) with broad-spectrum ROS scavenging capability can be used for psoriasis treatment and relapse prevention via related gene restoration. FeN4O2-SACs demonstrate attractive multiple enzyme-mimicking activities based on atomically dispersed Fe active structures, which are analogous to those of natural antioxidant enzymes, iron superoxide dismutase, human erythrocyte catalase, and ascorbate peroxidase. Further, in vitro and in vivo experiments show that FeN4O2-SACs can effectively ameliorate psoriasis-like symptoms and prevent the relapse with augmented efficacy compared with the clinical drug calcipotriol. Mechanistically, estrogen receptor 1 (ESR1) is identified as the core protein upregulated in psoriasis treatment through RNA sequencing and bioinformatic analysis. Together, this study provides a proof of concept of psoriasis catalytic therapy (PCT) and multienzyme-inspired bionics (MIB).

Compound effect and mechanism of oxidative damage induced by nanoplastics and benzo [a] pyrene

Nanoplastics and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soil environments. In order to objectively evaluate the toxic interaction between polystyrene nanoplastics (PS NPs) and benzo [a] pyrene (BaP), oxidative damage at the level of earthworm cells and biomacromolecules was investigated by experiments combined with molecular dynamics simulation. Studies on cells reveal that PS NPs and BaP had synergistic toxicity when it came to causing oxidative stress. Cellular reactive oxygen species (ROS) levels under combined pollutant exposure were 24% and 19% higher, respectively than when PS NPs and BaP were exposed alone (compared to the blank group). In addition, BaP and PS NPs inhibited the ability of CAT to decompose H2O2 by affecting the structure of the proximal amino acid Tyr 357 in the active center of CAT, which exacerbated oxidative stress to a certain extent. Therefore, the synergistic toxic effect of BaP and PS NPs is due to the mutual complement of the two to the induction of protein structural looseness, and the strengthening of the stability of the conjugate (CAT-BaP-PS) under the weak interaction. This work provides a new perspective and approach on how to talk about the toxicity of combined pollutants.

Involvement of antioxidant enzymes in Parkinson's disease

Similar to many other diseases, the etiology of Parkinson's disease (PD) is multifactorial and includes both genetic and environmental factors. Exposure to pesticides and the production of reactive oxygen species (ROS) in the body, mainly in electron transporter complexes 1 and 2 in the inner mitochondrial membrane, are two primary environmental risk factors for this disease. Increased accumulation of ROS and oxidative stress (OS) trigger a series of reactions that can lead to the aggregation of misfolded proteins, DNA damage, autophagy, and apoptosis, which may adversely affect cell function. These processes cause diseases such as coronary artery disease (CAD), Alzheimer's disease (AD), and PD. As indicated in previous studies, ROS is considered a critical regulator in the progression of PD. The human body contains several antioxidant molecules, such as vitamin A, vitamin C, bilirubin, and uric acid, as well as antioxidant enzymes including paraoxonase (PON), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD). Therefore, based on the canonical function of the antioxidant enzymes in PD, In the present review, we attempted to examine the function of antioxidant enzymes in PD.

Oxidative Stress in Healthy and Pathological Red Blood Cells

Red cell diseases encompass a group of inherited or acquired erythrocyte disorders that affect the structure, function, or production of red blood cells (RBCs). These disorders can lead to various clinical manifestations, including anemia, hemolysis, inflammation, and impaired oxygen-carrying capacity. Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense mechanisms, plays a significant role in the pathophysiology of red cell diseases. In this review, we discuss the most relevant oxidant species involved in RBC damage, the enzymatic and low molecular weight antioxidant systems that protect RBCs against oxidative injury, and finally, the role of oxidative stress in different red cell diseases, including sickle cell disease, glucose 6-phosphate dehydrogenase deficiency, and pyruvate kinase deficiency, highlighting the underlying mechanisms leading to pathological RBC phenotypes.

Design, Synthesis, and Biological Activity of Donepezil: Aromatic Amine Hybrids as Anti-Alzheimerss Drugs

In this study, benzylpiperidine, the active group of donepezil (DNP), was connected with the neurotransmitter phenylethylamine by square amide, in which the fat chain of phenylethylamine was reduced and the benzene rings were substituted. A series of multifunctional hybrid compounds, including DNP-aniline hybrids (1-8), DNP-benzylamine hybrids (9-14), and DNP-phenylethylamine hybrids (15-21) were obtained and their cholinesterase inhibitory activity and neuroprotection of the SH-SY5Y cell line were determined. Results showed that compound 3 exhibited excellent acetylcholinesterase inhibitory activity with an IC₅₀ value of 4.4 μM, higher than that of positive control DNP and significant neuroprotective effects against H₂O₂-induced oxidative damage in SH-SY5Y cells with 80.11% viability rate at 12.5 μM, much higher than that of the model group (viability rate = 53.1%). The mechanism of action of compound 3 was elucidated by molecular docking, reactive oxygen species (ROS), and immunofluorescence analysis. The results suggest that compound 3 could be further explored as a lead compound for the treatment of Alzheimer's disease. In addition, molecular docking research indicated that the square amide group formed strong interactions with the target protein. Based on the above analysis, we believe that square amide could be an interesting construction unit in anti-AD agents.

A catalase inhibitor: Targeting the NADPH-binding site for castration-resistant prostate cancer therapy

Catalase (CAT) is an important antioxidant enzyme that breaks down H₂O₂ into water and oxygen. Inhibitor-modulating CAT activity in cancer cells is emerging as a potential anticancer strategy. However, the discovery of CAT inhibitors towards the heme active center located at the bottom of long and narrow channel has made little progress. Therefore, targeting new binding site is of great importance for the development of efficient CAT inhibitors. Here, the first NADPH-binding site inhibitor of CAT, BT-Br, was designed and synthesized successfully. The cocrystal structure of BT-Br-bound CAT complex was determined with a resolution of 2.2 Å (PDB ID:8HID), which showed clearly that BT-Br bound at the NADPH-binding site. Furthermore, BT-Br was demonstrated to induce ferroptosis in castration-resistant prostate cancer (CRPC) DU145 cells and eventually reduce CRPC tumors in vivo effectively. The work indicates that CAT has potential as a novel target for CRPC therapy based on ferroptosis inducing.

Enhanced enzymatic activity and conformational stability of catalase in presence of tetrahedral DNA nanostructures: A biophysical and kinetic study

The emergence of DNA nanotechnology has shown enormous potential in a vast array of applications, particularly in the medicinal and theranostics fields. Nevertheless, the knowledge of the compatibility between DNA nanostructures and cellular proteins is largely unknown. Herein, we report the biophysical interaction between proteins (circulatory protein bovine serum albumin, BSA, and the cellular enzyme bovine liver catalase, BLC) and tetrahedral DNA (tDNAs), which are well-known nanocarriers for therapeutics. Interestingly, the secondary conformation of BSA or BLC was unaltered in the presence of tDNAs which supports the biocompatible property of tDNA. In addition, thermodynamic studies showed that the binding of tDNAs with BLC has a stable non-covalent interaction via hydrogen bond and van der Waals contact, which is indicative of a spontaneous reaction. Furthermore, the catalytic activity of BLC was increased in the presence of tDNAs during 24 h of incubation. These findings indicate that the presence of tDNA nanostructures not only ensures a steady secondary conformation of proteins, but also stabilize the intracellular proteins like BLC. Surprisingly, our investigation discovered that tDNAs have no effect on albumin proteins, either by interfering or by adhering to the extracellular proteins. These findings will aid in the design of future DNA nanostructures for biomedical applications by increasing the knowledge on the biocompatible interaction of tDNAs with biomacromolecules.

Catalase: A critical node in the regulation of cell fate

Catalase (CAT) is an extensively studied if somewhat enigmatic enzyme that is at the heart of eukaryotic antioxidant systems with a canonical role in peroxisomal function. The CAT family of proteins exert control over a wide range of plant growth and defence processes. CAT proteins are subject to many types of post-translational modification (PTM), which modify activity, ligand binding, stability, compartmentation and function. The CAT interactome involves many cytosolic and nuclear proteins that appear to be essential for protein functions. Hence, the CAT network of roles extends far beyond those associated with peroxisomal metabolism. Some pathogen effector proteins are able to redirect CAT to the nucleus and recent evidence indicates CAT can traffic to the nucleus in the absence of exogenous proteins. While the mechanisms that target CAT to the nucleus are not understood, CAT activity in the cytosol and nucleus is promoted by interactions with nucleoredoxin. Here we discuss recent findings that have been pivotal in generating a step change in our understanding of CAT functions in plant cells.

Invitro impact of a combination of red and infrared LEDs, infrared laser and magnetic field on biomarkers of oxidative stress and hemolysis of erythrocytes sampled from healthy individuals and diabetes patients

AIMS

Low-intensity infrared laser irradiation with output emissions of the laser and LED for in vitro irradiation of plasma and erythrocyte samples collected from healthy individuals and diabetes mellitus (DM) patients was used in the current study.

METHODS

The generated emission was in the range 0.85-0.89 nm with pulse duration near 130 ns and repetition rates of pulses 50, 150, 600, and 1500 Hz, average power 0, 50, or 100 mW, in the range of 1-9 min for different 30 variants of irradiation. The levels of 2-thiobarbituric-acid reactive substances (TBARS), aldehydic and ketonic derivatives of oxidatively modified proteins (OMP), total antioxidant capacity (TAC), acid-induced resistance of erythrocytes, and activities of the main antioxidant enzymes were assessed in erythrocyte and plasma samples after irradiation.

RESULTS

The low-intensity infrared laser irradiation and low-intensity light emitted by a red LED decreased the lipid peroxidation levels in the erythrocytes of both healthy individuals and DM patients. A statistically significant decrease in TBARS and OMP levels and an increase in the TAC level were observed at the irradiation energy of 34.39 and 68.79 J/cm² for samples collected from both healthy individuals and DM patients. The effects of the irradiation were accompanied by a statistically significant decrease in catalase activity of both healthy individuals and DM patients.

CONCLUSIONS

In many variants of the laser irradiation and low-intensity light emitted by a red LED used in our study, a decrease in the percent of hemolyzed erythrocytes was observed, suggesting that laser therapy protocols should take into account fluencies, frequencies, and wavelengths of the laser before the beginning of treatment, especially in DM patients.

Electron transfer-based antioxidant nanozymes: Emerging therapeutics for inflammatory diseases

Inflammatory diseases are usually featured with relatively high level of reactive oxygen species (ROS). The excess ROS facilitate the polarization of microphages into proinflammatory M1 phenotype, and cause DNA damage, protein carbonylation, and lipid peroxidation, resulting in further deterioration of inflammatory diseases. Therefore, alleviating oxidative stress by ROS scavenging has been an effective strategy for reversing inflammation. Inspired by the natural antioxidant enzymes, electron transfer-based artificial antioxidant nanozymes have been emerging therapeutics for the treatment of inflammatory diseases. The present review starts with the basic knowledge of ROS and diseases, followed by summarizing the possible active centers for the preparation of antioxidant nanozymes. The strategies for the design of antioxidant nanozymes on the purpose of higher catalytic activity are provided, and the applications of the developed antioxidant nanozymes on the therapy of inflammatory diseases are discussed. A perspective is included for the design and applications of artificial antioxidant nanozymes in biomedicine as well.

In silico prediction suggests inhibitory effect of halogenated boroxine on human catalase and carbonic anhydrase

Background

This research work included bioinformatics modeling of the dipotassium-trioxohydroxytetrafluorotriborate-halogenated boroxine molecule, as well as simulation and prediction of structural interactions between the halogenated boroxine molecule, human carbonic anhydrase, and human catalase structures. Using computational methods, we tried to confirm the inhibitory effect of halogenated boroxine on the active sites of these previously mentioned enzymes. The three-dimensional crystal structures of human catalase (PDB ID: 1DGB) and human carbonic anhydrase (PDB ID: 6FE2) were retrieved from RCSB Protein Data Bank and the protein preparation was performed using AutoDock Tools. ACD/ChemSketch and ChemDoodle were used for creating the three-dimensional structure of halogenated boroxine. Molecular docking was performed using AutoDock Vina, while the results were visualized using PyMOL.

Results

Results obtained in this research are showing evidence that there are interactions between the halogenated boroxine molecule and both previously mentioned proteins (human carbonic anhydrase and human catalase) in their active sites, which led us to the conclusion that the inhibitory function of halogenated boroxine has been confirmed.

Conclusion

These findings could be an important step in determining the exact mechanisms of inhibitory activity and will hopefully serve in further research purposes of complex pharmacogenomics studies.

Monofunctional Heme-Catalases

The review focuses on four issues that are critical for the understanding of monofunctional catalases. How hydrogen peroxide (H2O2) reaches the active site and outcompetes water molecules to be able to function at a very high rate is one of the issues examined. Part of the answer is a gate valve system that is instrumental to drive out solvent molecules from the final section of the main channel. A second issue relates to how the enzyme deals with an unproductive reactive compound I (Cpd I) intermediate. Peroxidatic two and one electron donors and the transfer of electrons to the active site from NADPH and other compounds are reviewed. The new ascribed catalase reactions are revised, indicating possible measurement pitfalls. A third issue concerns the heme b to heme d oxidation, why this reaction occurs only in some large-size subunit catalases (LSCs), and the possible role of singlet oxygen in this and other modifications. The formation of a covalent bond between the proximal tyrosine with the vicinal residue is analyzed. The last issue refers to the origin and function of the additional C-terminal domain (TD) of LSCs. The TD has a molecular chaperone activity that is traced to a gene fusion between a Hsp31-type chaperone and a small-size subunit catalase (SSC).

Quantitative Measurement of Cooperativity in H-Bonded Networks

Cooperative H-bonding interactions are a feature of supramolecular networks involving alcohols. A family of phenol oligomers, in which the hydroxyl groups form intramolecular H-bonds, was used to investigate this phenomenon. Chains of intramolecular H-bonds were characterized using nuclear magnetic resonance (NMR) spectroscopy in solution and X-ray crystallography in the solid state. The phenol oligomers were used to make quantitative measurements of the effects of the intramolecular interactions on the strengths of intermolecular H-bonding interactions between the H-bond donor on the end of the chain and a series of H-bond acceptors. Intramolecular H-bonding interactions in the chain increase the strength of a single intermolecular H-bond between the terminal phenol and quinuclidine by up to 14 kJ mol^–1 in the n-octane solution. Although the magnitude of the effect increases with the length of the H-bonded chain, the first intramolecular H-bond has a much larger effect than subsequent interactions. H-bond cooperativity is dominated by pairwise interactions between nearest neighbors, and longer range effects are negligible. The results were used to develop a simple model for cooperativity in H-bond networks using an empirical parameter κ to quantify the sensitivity of the H-bond properties of a functional group to polarization. The value of κ measured in these systems was 0.33, which means that formation of the first H-bond increases the polarity of the next H-bond donor in the chain by 33%. The cumulative cooperative effect in longer H-bonded chains reaches an asymptotic value, which corresponds to a maximum increase in the polarity of the terminal H-bond donor of 50%.

Chemical Composition of Various Nepeta cataria Plant Organs' Methanol Extracts Associated with In Vivo Hepatoprotective and Antigenotoxic Features as well as Molecular Modeling Investigations

This report summarizes the chemical composition analysis of Nepeta cataria L. flower, leaf, and stem methanol extracts (FME, LME, SME, respectively) as well as their hepatoprotective and antigenotoxic features in vivo and in silico. Herein, Wistar rat liver intoxication with CCl4 resulted in the generation of trichloromethyl and trichloromethylperoxy radicals, causing lipid peroxidation within the hepatocyte membranes (viz. hepatotoxicity), as well as the subsequent formation of aberrant rDNA adducts and consequent double-strand break (namely genotoxicity). Examined FME, LME, and SME administered orally to Wistar rats before the injection of CCl4 exerted the most notable pharmacological properties in the concentrations of 200, 100, and 50 mg/kg of body weight, respectively. Thus, the extracts' hepatoprotective features were determined by monitoring the catalytic activities of enzymes and the concentrations of reactive oxidative species, modulating the liver redox status. Furthermore, the necrosis of hepatocytes was assessed by means of catalytic activities of liver toxicity markers. The extracts' antigenotoxic features were quantified using the comet assay. Distinct pharmacological property features may be attributed to quercitrin (8406.31 μg/g), chlorogenic acid (1647.32 μg/g), and quinic acid (536.11 μg/g), found within the FME, rosmarinic acid (1056.14 μg/g), and chlorogenic acid (648.52 μg/g), occurring within the LME, and chlorogenic acid (1408.43 μg/g), the most abundant in SME. Hence, the plant's secondary metabolites were individually administered similar to extracts, upon which their pharmacology in vivo was elucidated in silico by means of the structure-based studies within rat catalase, as a redox marker, and rat topoisomerase IIα, an enzyme catalyzing the rat DNA double-strand break. Conclusively, the examined N. cataria extracts in specified concentrations could be used in clinical therapy for the prevention of toxin-induced liver diseases.

Cucumis melo var. momordica as a potent antidiabetic, antioxidant and possible anticovid alternative: Investigation through experimental and computational methods

Diabetes mellitus is a typical life threatening of disease, which generate due to the dysfunction of β cells of pancreas. In 2014, WHO stated that 422 million people were infected with DM. The current pattern of management of diabetes included synthetic or plant based oral hypoglycemic drugs and insulin but drug resentence is become a very big issues in antidiabetic therapy. Thus, it's very earnest to discover now medication for this disease. Now the days, it is well acknowledged that diabetic patients are more prone towards covid and related complications. Thus, medical practitioners reformed the methodology of prescribing medication for covid infected antidiabetic therapy and encouraging the medication contains dual pharmacological properties. It is also well know that polyphenols specifically hold a significant role in oxidative stress and reduced the severity of many inflammatory diseases. Cucumis melo has rich history as ethano-pharmacological use in Indian subcontinent. The fruit and seed is well known for the treatment of various diseases due to the presence of phenolics. Therefore, in this study, the combined mixture of flower and seeds were used for the extraction of polyphenolic rich extract and tested for antidiabetic activity through the antioxidant and in vivo experiments. The antioxidant potential measurement exhibited that the selected plant  has the significant competence to down-regulate oxidative stress (DPPH scavenging IC 50 at 60.7 ±1.05 µg/mL, ABTS IC 50 at 62.15 ± 0.50 µg/mL). Furthermore, the major polyphenolic phyto-compounds derived from the Cucumis melo were used for in silico anticovid activity, docking, and complementarity studies. The anticovid activity prognosis reflected that selected phyto-compounds amentoflavone and vanillic acid have optimal possibility to interact with 3C-like protease and through this moderate anticovid activity can be exhibit. The docking experiments established that the selected compounds have propensity to interact with protein tyrosine phosphatase 1B, 11β-Hydroxysteroid dehydrogenase, superoxide dismutase, glutathione peroxidase, and catalase β-glucuronidase receptor. In vivo experiments showed that 500 mg/kg, Cucumis melo ominously amplified body weight, plasma insulin, high-density lipoprotein levels, and biochemical markers. Furthermore, extract significantly downregulate the blood glucose, total cholesterol, triglycerides, low-density lipoprotein, and very low-density lipoprotein.

A combined in vitro-in silico approach for the discovery of novel endogenous enzymatic and ctDNA sequence of bioactive molecules from aerial and root parts of Centaurea sulphurea as antioxidant's agents

The excess free radicals not neutralized by the antioxidant defenses damage the essential macromolecules of our cells, causing abnormalities in the expression of genes and membrane receptors, cell proliferation or death, immune disorders, mutagenesis, deposits of proteins or lipofuschin in tissues. The first objective of this study was to elucidate the composition of the essential oil of the aerial and root part of Centaurea sulphurea during beginning of the vegetative cycle (March), beginning of the flowering stage (April) and full bloom (May/June) using GC/FID and GC/MS. The second aim was to describe the antioxidant activity using three methods (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), β-carotene bleaching assay) and bioinformatical study of ctDNA sequence and three endogenous enzymes inhibition. The essential oils obtained from the root during the full bloom period consisted mainly of caryophyllene oxide, aplotaxene and (Z)-phytol. While, the aerial parts were dominated by caryophyllene oxide, verridiflorol and humulene epoxide II. The results showed that essential oil presented an excellent antioxidant activity with IC₅₀ values of 2.06 g/L and 1.29 g/L, for aerial and root parts, compared to butylated hydroxyltoluene (BHT) and Ethylenediaminetetraacetic acid (EDTA) controls and the nicotinamide adenine dinucleotide phosphate (NADPH) co-crystallized inhibitor. The results of the molecular docking revealed that (Z)-phytol (Ligand 39) has an affinity to interact with ctDNA sequence, and three targets Endogenous enzymes. The molecular dynamics study was conducted for the best inhibitors (Z)-phytol. A few key residues were identified at the binding site of receptors. The in-silico assessment of the ADME properties and BOILED-Egg plot reveals that compound (Z)-phytol (L39) is permeable to the blood brain barrier and have high lipophilicity and high coefficient of skin permeability in the intestines with good bioavailability. The ADMET analysis also showed that this oxygenated diterpene is safer to replace the synthetic drugs with side effects. Further testing is needed to assess its effectiveness in reducing oxidative stress for use in the pharmaceutical industry.Communicated by Ramaswamy H. Sarma.

Catalase Inhibition by Aminoalkanol Derivatives with Potential Anti-Cancer Activity-In Vitro and In Silico Studies Using Capillary Electrophoresis Method

In this work, the investigation of type and inhibitory strength of catalase by two pairs of aminoalkanol derivatives (1,7 diEthyl- and 1,7-diMethyl-8,9-diphenyl-4-azatricyclo (5.2.1.02.6) dec-8-ene- 3,5,10-trione) has been presented. The obtained results allowed for the determination of all kinetic parameters (Km, Vmax, slope angles of Lineweaver-Burk plots, Ki and IC50) on the basis of which it was shown that all four aminoalkanol derivatives are competitive inhibitors of catalase. However, the strength of action of each of them depends on the type of substituents present in the main structure of the molecule. Subtle differences in the potency of individual derivatives were possible to detect thanks to the developed, sensitive method of capillary electrophoresis, which allowed simultaneous monitoring of the mutual changes in the concentrations of substrates and products of the reaction catalyzed by the enzyme. Detailed values of kinetic parameters showed that all derivatives are weak inhibitors of catalase, which in this case is a big advantage because each inhibition of catalase activity is associated with a greater amount of accumulated, harmful reactive oxygen species. The results of docking studies also show the convergence of the binding energies values of individual inhibitors with all kinetic parameters of the investigated catalase inhibition and thus additionally confirm the weak inhibitory strength of all four aminoalkanol derivatives.

Singlet Oxygen, Photodynamic Therapy, and Mechanisms of Cancer Cell Death

Photodynamic therapy (PDT) can be developed into an important arsenal against cancer; it is a minimally invasive therapy, which is used in the treatment or/and palliation of a variety of cancers and benign diseases. The removal of cancerous tissue is achieved with the use of photosensitizer and a light source, which excites the photosensitizer. This excitation causes the photosensitizer to generate singlet oxygen and other reactive oxygen species. PDT has been used in several types of cancers including nonmelanoma skin cancer, bladder cancer, esophageal cancer, head and neck cancer, and non-small cell lung cancer (NSCLC). Although it is routinely used in nonmelanoma skin cancer, it has not been widely adopted in other solid cancers due to a lack of clinical data showing the superiority of PDT over other forms of treatment. Singlet oxygen used in PDT can alter the activity of the catalase, which induces immunomodulation through HOCl signaling. The singlet oxygen can induce apoptosis through both the extrinsic and intrinsic pathways. The extrinsic pathway of apoptosis starts with the activation of the Fas receptor by singlet oxygen that leads to activation of the caspase-7 and caspase-3. In the case of the intrinsic pathway, disruption caused by singlet oxygen in the mitochondria membrane leads to the release of cytochrome c, which binds with APAF-1 and procaspase-9, forming a complex, which activates caspase-3. Mechanisms of PDT action can vary according to organelles affected. In the plasma membrane, membrane disruption is caused by the oxidative stress leading to the intake of calcium ions, which causes swelling and rupture of cells due to excess intake of water, whereas disruption of lysosome causes the release of the cathepsins B and D, which cleave Bid into tBid, which changes the mitochondrial outer membrane permeability (MOMP). Oxidative stress causes misfolding of protein in the endoplasmic reticulum. When misfolding exceeds the threshold, it triggers unfolding protein response (UPR), which leads to activation of caspase-9 and caspase-3. Finally, the activation of p38 MAPK works as an alternative pathway for the induction of MOMP.

Modulation of Reactive Oxygen Species Homeostasis as a Pleiotropic Effect of Commonly Used Drugs

Age-associated diseases represent a growing burden for global health systems in our aging society. Consequently, we urgently need innovative strategies to counteract these pathological disturbances. Overwhelming generation of reactive oxygen species (ROS) is associated with age-related damage, leading to cellular dysfunction and, ultimately, diseases. However, low-dose ROS act as crucial signaling molecules and inducers of a vaccination-like response to boost antioxidant defense mechanisms, known as mitohormesis. Consequently, modulation of ROS homeostasis by nutrition, exercise, or pharmacological interventions is critical in aging. Numerous nutrients and approved drugs exhibit pleiotropic effects on ROS homeostasis. In the current review, we provide an overview of drugs affecting ROS generation and ROS detoxification and evaluate the potential of these effects to counteract the development and progression of age-related diseases. In case of inflammation-related dysfunctions, cardiovascular- and neurodegenerative diseases, it might be essential to strengthen antioxidant defense mechanisms in advance by low ROS level rises to boost the individual ROS defense mechanisms. In contrast, induction of overwhelming ROS production might be helpful to fight pathogens and kill cancer cells. While we outline the potential of ROS manipulation to counteract age-related dysfunction and diseases, we also raise the question about the proper intervention time and dosage.

The Intestinal Redox System and Its Significance in Chemotherapy-Induced Intestinal Mucositis

Chemotherapy-induced intestinal mucositis (CIM) is a significant dose-limiting adverse reaction brought on by the cancer treatment. Multiple studies reported that reactive oxygen species (ROS) is rapidly produced during the initial stages of chemotherapy, when the drugs elicit direct damage to intestinal mucosal cells, which, in turn, results in necrosis, mitochondrial dysfunction, and ROS production. However, the mechanism behind the intestinal redox system-based induction of intestinal mucosal injury and necrosis of CIM is still undetermined. In this article, we summarized relevant information regarding the intestinal redox system, including the composition and regulation of redox enzymes, ROS generation, and its regulation in the intestine. We innovatively proposed the intestinal redox “Tai Chi” theory and revealed its significance in the pathogenesis of CIM. We also conducted an extensive review of the English language-based literatures involving oxidative stress (OS) and its involvement in the pathological mechanisms of CIM. From the date of inception till July 31, 2021, 51 related articles were selected. Based on our analysis of these articles, only five chemotherapeutic drugs, namely, MTX, 5-FU, cisplatin, CPT-11, and oxaliplatin were shown to trigger the ROS-based pathological mechanisms of CIM. We also discussed the redox system-mediated modulation of CIM pathogenesis via elaboration of the relationship between chemotherapeutic drugs and the redox system. It is our belief that this overview of the intestinal redox system and its role in CIM pathogenesis will greatly enhance research direction and improve CIM management in the future.

Bioinorganic Chemistry on Electrodes: Methods to Functional Modeling

One of the major goals of bioinorganic chemistry has been to mimic the function of elegant metalloenzymes. Such functional modeling has been difficult to attain in solution, in particular, for reactions that require multiple protons and multiple electrons (nH⁺/ne^-). Using a combination of heterogeneous electrochemistry, electrode and molecule design one may control both electron transfer (ET) and proton transfer (PT) of these nH⁺/ne^- reactions. Such control can allow functional modeling of hydrogenases (H⁺ + e^- → 1/2 H₂), cytochrome c oxidase (O₂ + 4 e^- + 4 H⁺ → 2 H₂O), monooxygenases (RR'CH₂ + O₂ + 2 e^- + 2 H⁺ → RR'CHOH + H₂O) and dioxygenases (S + O₂ → SO₂; S = organic substrate) in aqueous medium and at room temperatures. In addition, these heterogeneous constructs allow probing unnatural bioinspired reactions and estimation of the inner- and outer-sphere reorganization energy of small molecules and proteins.