Exploring the Esterase Catalytic Activity of Minimalist Heptapeptide Amyloid Fibers.

This paper investigates the esterase activity of minimalist amyloid fibers composed of short seven-residue peptides, IHIHIHI (IH7) and IHIHIQI (IH7Q), with a particular focus on the role of the sixth residue position within the peptide sequence. Through computational simulations and analyses, we explore the molecular mechanisms underlying catalysis in these amyloid-based enzymes. Contrary to initial hypotheses, our study reveals that the twist angle of the fiber, and thus the catalytic site's environment, is not notably affected by the sixth residue. Instead, the sixth residue interacts with the p-nitrophenylacetate (pNPA) substrate, particularly through its -NO2 group, potentially enhancing catalysis. Quantum mechanics/molecular mechanics (QM/MM) simulations of the reaction mechanism suggest that the polarizing effect of glutamine enhances catalytic activity by forming a stabilizing network of hydrogen bonds with pNPA, leading to lower energy barriers and a more exergonic reaction. Our findings provide valuable insights into the intricate interplay between peptide sequence, structural arrangement, and catalytic function in amyloid-based enzymes, offering potentially valuable information for the design and optimization of biomimetic catalysts.

Biochemical characterization of an esterase from Thermobifida fusca YX with acetyl xylan esterase activity.

BACKGROUND: Esterases (EC 3.1.1.X) are enzymes that catalyze the hydrolysis ester bonds. These enzymes have large potential for diverse applications in fine industries, particularly in pharmaceuticals, cosmetics, and bioethanol production. METHODS AND RESULTS: In this study, a gene encoding an esterase from Thermobifida fusca YX (TfEst) was successfully cloned, and its product was overexpressed in Escherichia coli and purified using affinity chromatography. The TfEst kinetic assay revealed catalytic efficiencies of 0.58 s-1 mM-1, 1.09 s-1 mM-1, and 0.062 s-1 mM-1 against p-Nitrophenyl acetate, p-Nitrophenyl butyrate, and 1-naphthyl acetate substrates, respectively. Furthermore, TfEst also exhibited activity in a pH range from 6.0 to 10.0, with maximum activity at pH 8.0. The enzyme demonstrated a half-life of 20 min at 70 °C. Notably, TfEst displayed acetyl xylan esterase activity as evidenced by the acetylated xylan assay. The structural prediction of TfEst using AlphaFold indicated that has an α/ß-hydrolase fold, which is consistent with other esterases. CONCLUSIONS: The enzyme stability over a broad pH range and its activity at elevated temperatures make it an appealing candidate for industrial processes. Overall, TfEst emerges as a promising enzymatic tool with significant implications for the advancement of biotechnology and biofuels industries.

Molecular insight on the binding of halogenated organic phosphate esters to human serum albumin and its effect on cytotoxicity of halogenated organic phosphate esters.

Halogenated Organic Phosphate Esters (OPEs) are commonly found in plasticizers and flame retardants. However, they are one kind of persistent contaminants that can pose a significant threat to human health and ecosystem as new environmental estrogen. In this study, two representative halogenated OPEs, tris(1,3-dichloro-2-propyl) phosphate (TDCP) and tris(2,3-dibromopropyl) phosphate (TDBP), were selected as experimental subjects to investigate their interaction with human serum albumin (HSA). Despite having similar structures, the two ligands exhibited contrasting effects on enzyme activity of HSA, TDCP inhibiting enzyme activity and TDBP activating it. Furthermore, both TDCP and TDBP could bind to HSA at site I, interacted with Arg222 and other residues, and made the conformation of HSA unfolded. Thermodynamic parameters indicated the main driving forces between TDBP and HSA were hydrogen bonding and van der Waals forces, while TDCP was mainly hydrophobic force. Molecular simulations found that more hydrogen bonds of HSA-TDBP formed during the binding process, and the larger charge area of TDBP than TDCP could partially account for the differences observed in their binding abilities to HSA. Notably, the cytotoxicity of TDBP/TDCP was inversely proportional to their binding ability to HSA, implying a new method for determining the cytotoxicity of halogenated OPEs in vitro.

Unlocking prophage potential: In silico and experimental analysis of a novel Mycobacterium fortuitum LysinB containing a peptidoglycan-binding domain.

Endolysins are highly evolved bacteriophage-encoded lytic enzymes produced to damage the bacterial cell wall for phage progeny release. They offer promising potential as highly specific lytic proteins with a low chance of bacterial resistance. The diversity in lysin sequences and domain organization can be staggering. In silico analysis of bacteriophage and prophage genomes can help identify endolysins exhibiting unique features and high antibacterial activity, hence feeding the pipeline of narrow-spectrum protein antibiotics. Mycobacteriophage lysis cassettes mostly have two lytic enzymes, LysinA and LysinB. The enzyme LysinA targets peptidoglycan in the cell wall and possesses a modular architecture. LysinB typically contains a single domain and acts upon the mycolyl ester linkages in mycolyl-arabinogalactan-peptidoglycan (Payne et al., 2010). This study aimed to find novel LysinBs against Mycobacterium fortuitum. After a detailed in silico characterization of lysis cassettes from three M. fortuitum prophages, we chose to work on a LysinB (hereafter described as LysinB_MF) found in an incomplete prophage (phiE1336, 9.4 kb in strain E1336). LysinB_MF showed low sequence similarity with any other endolysins in the database and formed a separate clade on phylogenetic analysis. LysinB_MF's structure, extracted from the AlphaFold Protein Structure Database, demonstrated a modular architecture with two structurally distinct domains: a peptidoglycan-binding domain (PGBD) at the N-terminal and the characteristic alpha/beta hydrolase domain connected via a linker peptide. We found the alpha/beta hydrolase domain, which is the enzyme-active domain (EAD), contains the conserved Ser-Asp-His catalytic triad with a tunnel-like topology and forms intermolecular hydrogen bonds. The PGBD shows structural similarity to the cell-wall binding domain of an amidase from Clostridium acetobutylicum, hinting at its acquisition due to domain mobility. Our in silico electrostatic potential analysis suggested that PGBD might be essential to the enzyme activity. This was experimentally validated by generating a truncated version of the enzyme, which demonstrated about six-fold decreased activity compared to its native form. The antimycobacterial activity of this enzyme was also compromised in its absence. Based on our analysis, PGBD emerged as an integral constituent of enzymes with diverse functional properties and is predicted to be a conserved cross-kingdom. Overall, this study highlights the importance of mining mycobacterial prophages as a novel endolysin source. It also provides unique insights into the diverse architecture of mycobacteriophage-encoded endolysins and the importance of functional domains for their catalytic activities.

A novel and efficient strategy for the biodegradation of di(2-ethylhexyl) phthalate by Fusarium culmorum.

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer that is used worldwide and raises concerns because of its prevalence in the environment and potential toxicity. Herein, the capability of Fusarium culmorum to degrade a high concentration (3 g/L) of DEHP as the sole carbon and energy source in solid-state fermentation (SSF) was studied. Cultures grown on glucose were used as controls. The biodegradation of DEHP by F. culmorum reached 96.9% within 312 h. This fungus produced a 3-fold higher esterase activity in DEHP-supplemented cultures than in control cultures (1288.9 and 443.2 U/L, respectively). In DEHP-supplemented cultures, nine bands with esterase activity (24.6, 31.2, 34.2, 39.5, 42.8, 62.1, 74.5, 134.5, and 214.5 kDa) were observed by zymography, which were different from those in control cultures and from those previously reported for cultures grown in submerged fermentation. This is the first study to report the DEHP biodegradation pathway by a microorganism grown in SSF. The study findings uncovered a novel biodegradation strategy by which high concentrations of DEHP could be biodegraded using two alternative pathways simultaneously. F. culmorum has an outstanding capability to efficiently degrade DEHP by inducing esterase production, representing an ecologically promising alternative for the development of environmental biotechnologies, which might help mitigate the negative impacts of environmental contamination by this phthalate. KEY POINTS: • F. culmorum has potential to tolerate and remove di(2-ethylhexyl) phthalate (DEHP) • Solid-state fermentation is an efficient system for DEHP degradation by F. culmorum • High concentrations of DEHP induce high levels of esterase production by F. culmorum.

Efficacy of Citrullus colocynthis seed extract on Earias vittella, Fabricius, (Lepidoptera: Noctuidae): environment sustainable approach

Abstract Earias vittellaFabricius, 1794 (Noctuidae: Lepidoptera) is deliberated to be one of the most destructive pests of cotton and okra vegetation in the world including Asia. The pest has established resistance to various synthetic insecticides. The use of bio-pesticide is one of the unconventional approaches to develop a vigorous ecosystem without harming non- target pests and beneficial natural insect fauna. In the present study, the toxicity levels of Citrullus colocynthis seed extract have been evaluated against the populations of E. vittellaunder standardized laboratory conditions. The toxic effects of C. colocynthis on development periods, protein contents and esterase activity of the life stages of E. vittella were also evaluated. The toxicity levels of methanol, ethanol, hexane, water and profenofos were evaluated on the 1st instar larvae of E. vittella. LC30 and LC80 concentrations exhibited the effectiveness of methanol-based C. colocynthis seed extract against 1st instar larvae of E. vitella. The enhanced larval and pupal periods were revealed in treated samples during the comparison with untreated samples. The intrinsic rate of increase, net reproductive rate in the LC30 and LC80 concentrations exposed larvae remained less than the control treatment. Fecundity, the esterase activity and protein contents were declined in LC30 and LC80 treated samples as compared to the control. The present findings suggest that C. colosynthis extracts based botanical insecticides are beneficial, ecosystem sustainable and can be integrated with insect management programs from environment safety perspective.

Resumo Earias vittella Fabricius, 1794 (Noctuidae: Lepidoptera) é considerada uma das pragas mais destrutivas de algodão e quiabo no mundo, incluindo a Ásia. Essa praga estabeleceu resistência a vários inseticidas sintéticos. O uso de biopesticidas é uma das abordagens não convencionais para desenvolver um ecossistema saudável sem prejudicar as pragas não alvo e a fauna natural benéfica de insetos. No presente estudo, os níveis de toxicidade do extrato de semente de Citrullus colocynthis foram avaliados nas populações de E. vittella em condições de laboratório padronizadas. Os efeitos tóxicos de C. colocynthis nos períodos de desenvolvimento, conteúdo de proteína e atividade esterase das fases de vida de E. vittella também foram avaliados. Os níveis de toxicidade de metanol, etanol, hexano, água e profenofós foram avaliados em larvas de 1º instar de E. vittella. As concentrações de LC30 e LC80 apresentaram eficácia do extrato de sementes de C. colocynthis à base de metanol contra larvas de 1º instar de E. vittella. Os períodos larval e pupal aumentados foram revelados nas amostras tratadas durante a comparação com as amostras não tratadas. A taxa intrínseca de aumento e a taxa reprodutiva líquida nas concentrações de larvas expostas LC30 e LC80 permaneceram menores do que o tratamento controle. A fecundidade, a atividade da esterase e o conteúdo de proteína diminuíram nas amostras tratadas com LC30 e LC80 em comparação com o controle. As presentes descobertas sugerem que os extratos de C. colocynthis à base de inseticidas botânicos são benéficos, sustentáveis para o ecossistema e podem ser integrados com programas de manejo de insetos do ponto de vista da segurança ambiental.

Efficacy of Citrullus colocynthis seed extract on Earias vittella, Fabricius, (Lepidoptera: Noctuidae): environment sustainable approach / Eficácia do extrato de semente de Citrullus colocynthis em Earias vittella Fabricius (Lepidoptera: Noctuidae): abordagem ambiental sustentável

Abstract Earias vittellaFabricius, 1794 (Noctuidae: Lepidoptera) is deliberated to be one of the most destructive pests of cotton and okra vegetation in the world including Asia. The pest has established resistance to various synthetic insecticides. The use of bio-pesticide is one of the unconventional approaches to develop a vigorous ecosystem without harming non- target pests and beneficial natural insect fauna. In the present study, the toxicity levels of Citrullus colocynthis seed extract have been evaluated against the populations of E. vittellaunder standardized laboratory conditions. The toxic effects of C. colocynthis on development periods, protein contents and esterase activity of the life stages of E. vittella were also evaluated. The toxicity levels of methanol, ethanol, hexane, water and profenofos were evaluated on the 1st instar larvae of E. vittella. LC30 and LC80 concentrations exhibited the effectiveness of methanol-based C. colocynthis seed extract against 1st instar larvae of E. vitella. The enhanced larval and pupal periods were revealed in treated samples during the comparison with untreated samples. The intrinsic rate of increase, net reproductive rate in the LC30 and LC80 concentrations exposed larvae remained less than the control treatment. Fecundity, the esterase activity and protein contents were declined in LC30 and LC80 treated samples as compared to the control. The present findings suggest that C. colosynthis extracts based botanical insecticides are beneficial, ecosystem sustainable and can be integrated with insect management programs from environment safety perspective.

Resumo Earias vittella Fabricius, 1794 (Noctuidae: Lepidoptera) é considerada uma das pragas mais destrutivas de algodão e quiabo no mundo, incluindo a Ásia. Essa praga estabeleceu resistência a vários inseticidas sintéticos. O uso de biopesticidas é uma das abordagens não convencionais para desenvolver um ecossistema saudável sem prejudicar as pragas não alvo e a fauna natural benéfica de insetos. No presente estudo, os níveis de toxicidade do extrato de semente de Citrullus colocynthis foram avaliados nas populações de E. vittella em condições de laboratório padronizadas. Os efeitos tóxicos de C. colocynthis nos períodos de desenvolvimento, conteúdo de proteína e atividade esterase das fases de vida de E. vittella também foram avaliados. Os níveis de toxicidade de metanol, etanol, hexano, água e profenofós foram avaliados em larvas de 1º instar de E. vittella. As concentrações de LC30 e LC80 apresentaram eficácia do extrato de sementes de C. colocynthis à base de metanol contra larvas de 1º instar de E. vittella. Os períodos larval e pupal aumentados foram revelados nas amostras tratadas durante a comparação com as amostras não tratadas. A taxa intrínseca de aumento e a taxa reprodutiva líquida nas concentrações de larvas expostas LC30 e LC80 permaneceram menores do que o tratamento controle. A fecundidade, a atividade da esterase e o conteúdo de proteína diminuíram nas amostras tratadas com LC30 e LC80 em comparação com o controle. As presentes descobertas sugerem que os extratos de C. colocynthis à base de inseticidas botânicos são benéficos, sustentáveis ​​para o ecossistema e podem ser integrados com programas de manejo de insetos do ponto de vista da segurança ambiental.

Exploring the effect of surfactants on the interactions of manganese dioxide nanoparticles with biomolecules.

Interactions of manganese dioxide nanoparticles (MnO2 NPs) with vital biomolecules namely deoxyribonucleic acid (DNA) and serum albumin (BSA) have been studied in association with different surfactants by using fluorescence (steady state, synchronous and 3D), UV-visible, resonance light scattering (RLS), dynamic light scattering (DLS), and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The esterase activity of serum albumin was tested in associations with MnO2 NPs and surfactants. The antioxidant potential of prepared NPs was also evaluated (DPPH method). Gel electrophoresis was carried out to analyze the effect of MnO2 NPs and surfactants on DNA. Presence of CTAB, Tween 20, DTAB and Tween 80 enhanced nanoparticle-protein binding. Tween 20 based nanoparticle systems showed long-term stability and biocompatibility. The quenching of BSA fluorescence emission in presence of MnO2 NPs alone and along with Tween 20 revealed stronger association of nanoparticles with proteins. Enhancement in the esterase activity (BSA) was observed in the presence of Tween 20. Furthermore, radical scavenging activity showed highest antioxidant potential in presence of Tween 20. The enthalpy and entropy assessment for protein-NPs association showed the predominance of Vander Waals interactions and hydrogen bonding. The synchronous fluorescence analysis highlighted the involvement of tryptophan (Trp) in the MnO2 NPs-protein interactions. The study evaluates the influence of surfactant on the associations of MnO2 NPs with the essential biomolecules. The findings can be crucially utilized in designing biocompatible MnO2 formulations for long term applications.Communicated by Ramaswamy H. Sarma.

Effects of Phosphorylation on the Activity, Inhibition and Stability of Carbonic Anhydrases.

Carbonic anhydrases (CAs) are a metalloenzyme family that have important roles in cellular processes including pH homeostasis and have been implicated in multiple pathological conditions. Small molecule inhibitors have been developed to target carbonic anhydrases, but the effects of post-translational modifications (PTMs) on the activity and inhibition profiles of these enzymes remain unclear. Here, we investigate the effects of phosphorylation, the most prevalent carbonic anhydrase PTM, on the activities and drug-binding affinities of human CAI and CAII, two heavily modified active isozymes. Using serine to glutamic acid (S > E) mutations to mimic the effect of phosphorylation, we demonstrate that phosphomimics at a single site can significantly increase or decrease the catalytic efficiencies of CAs, depending on both the position of the modification and the CA isoform. We also show that the S > E mutation at Ser50 of hCAII decreases the binding affinities of hCAII with well-characterized sulphonamide inhibitors including by over 800-fold for acetazolamide. Our findings suggest that CA phosphorylation may serve as a regulatory mechanism for enzymatic activity, and affect the binding affinity and specificity of small, drug and drug-like molecules. This work should motivate future studies examining the PTM-modification forms of CAs and their distributions, which should provide insights into CA physiopathological functions and facilitate the development of 'modform-specific' carbonic anhydrase inhibitors.

Black Pepper (Piper nigrum) Alleviates Oxidative Stress, Exerts Potential Anti-Glycation and Anti-AChE Activity: A Multitargeting Neuroprotective Agent against Neurodegenerative Diseases.

Neurodegenerative diseases (NDs) are a family of disorders that cause progressive structural and functional degeneration of neurons. Among all the organs in the body, the brain is the one that is the most affected by the production and accumulation of ROS. Various studies have shown that an increase in oxidative stress is a common pathophysiology for almost all NDs, which further affects various other pathways. The available drugs lack the wide spectrum necessary to confront these complexities altogether. Hence, a safe therapeutic approach to target multiple pathways is highly desirable. In the present study, the hexane and ethyl acetate extracts of Piper nigrum (black pepper), an important spice, were evaluated for their neuroprotective potential in hydrogen peroxide-induced oxidative stress in human neuroblastoma cells (SH-SY5Y). The extracts were also subjected to GC/MS to identify the important bioactives present. The extracts exhibited neuroprotection by significantly decreasing the oxidative stress and restoring the mitochondrial membrane potential in the cells. Additionally, the extracts displayed potent anti-glycation and significant anti-Aß fibrilization activities. The extracts were competitive inhibitors of AChE. The multitarget neuroprotective mechanism displayed by Piper nigrum indicates it as a potential candidate in the treatment of NDs.

Multi-Targeting Neuroprotective Effects of Syzygium aromaticum Bud Extracts and Their Key Phytocompounds against Neurodegenerative Diseases.

Alzheimer's disease (AD) is a neurodegenerative disease that causes a gradual loss of normal motor and cognitive function. The complex AD pathophysiology involves various factors such as oxidative stress, neuroinflammation, amyloid-beta (Aß) aggregation, disturbed neurotransmission, and apoptosis. The available drugs suffer from a range of side effects and are not able to cover different aspects of the disease. Therefore, finding a safer therapeutic approach that can affect multiple targets at a time is highly desirable. In the present study, the underlying neuroprotective mechanism of an important culinary spice, Syzygium aromaticum (Clove) extract, and major bioactive compounds were studied in hydrogen peroxide-induced oxidative stress in human neuroblastoma SH-SY5Y cell lines as a model. The extracts were subjected to GC-MS to identify important bioactive components. The extracts and key bio-actives reduced reactive oxygen species (ROS), restored mitochondrial membrane potential (MMP), and provided neuroprotection from H2O2-induced oxidative stress in cell-based assays due to the antioxidant action. They also reduced lipid peroxidation significantly and restored GSH content. Clove extracts have also displayed anti-acetylcholinesterase (AChE) activity, anti-glycation potential, and Aß aggregation/fibrilization inhibition. The multitarget neuroprotective approach displayed by Clove makes it a potential candidate for AD drug development.

In-Package Atmospheric Cold Plasma Treatment and Storage Effects on Membrane Integrity, Oxidative Stress, and Esterase Activity of Listeria monocytogenes.

Atmospheric cold plasma (ACP) treatment can reduce bacterial pathogens in foods. Additional reduction in bacterial cells during storage after ACP treatment was previously reported. The underlying mechanisms of bacterial inactivation during ACP treatment and post-treatment storage need to be understood. This study investigated the changes in the morpho-physiological status of Listeria monocytogenes on ham surfaces after post-ACP-treatment storage of 1 h, 24 h, and 7 days at 4 °C. The membrane integrity, intracellular oxidative stress, and esterase activity of L. monocytogenes were evaluated by flow cytometry. L. monocytogenes cells were under high oxidative stress conditions with slightly permeabilized membranes after 1 h of post-ACP-treatment storage according to the flow cytometry data. During the extended storage of 24 h, the percentage of cells with a slightly permeabilized membrane increased; subsequently, the percentage of cells with intact membranes decreased. The percentage of L. monocytogenes cells with intact membranes decreased to <5% with a treatment time of 10 min and after 7 days of post-treatment storage. In addition, the percentage of L. monocytogenes cells under oxidation stress decreased to <1%, whereas the percentage of cells with completely permeabilized membranes increased to more than 90% for samples treated with ACP for 10 min and 7 days of post-treatment storage. With increased ACP treatment time, for 1 h stored samples, the percentage of cells with active esterase and slightly permeabilized membranes increased. However, during the extended post-treatment storage of 7 days, the percentage of cells with active esterase and slightly permeabilized membranes decreased to below 1%. At the same time, the percentage of cells with permeabilized membrane increased to more than 92% with an increase in ACP treatment time of 10 min. In conclusion, the higher inactivation after 24 h and 7 days post-ACP-treatment storage compared to 1 h stored samples correlated with the loss of esterase activity and membrane integrity of L. monocytogenes cells.

Tissue-specific assessment of oxidative status: Wild boar as a case study.

In recent decades, there has been a fast-growing interest in using biomarkers of oxidative stress (BOS) in conservation programs of many vertebrate species. Biomarkers of oxidative stress can be measured in different biological samples (e.g., body fluids and tissues). However, since comparisons of the same battery of BOS among tissues of the same individual are scarce in the literature, the chosen target tissues regularly rely on arbitrary decisions. Our research aimed to determine if the oxidative status of free-ranging wild boar (Sus scrofa) naturally infected with Mycobacterium spp (etiological agent of tuberculosis, TB), varies depending on the sample where it was quantified. We compared antioxidant p-nitrophenyl esterase activity (EA), glutathione peroxidase (GPX) concentrations, and total oxidative status (TOS) in serum, lung, spleen, kidney, and muscle of 63 wild boar hunter-harvested in central Spain. Biomarkers of oxidative stress in serum had higher concentrations than in other tissues. The poor agreement between serum and other tissues highlights the importance of running complete BOS assessments in the same fluid or tissue. Further, low concentrations of BOS in tissues of TB-affected individuals were observed, and significant differences between healthy and sick boar were only detected in the serum of individuals developing mild TB and in the muscle of individuals with mild or severe disease status. However, all organs from wild boars affected with mild TB were not in oxidative imbalance compared to healthy control animals, suggesting that wild boars may cope well with TB. Our data indicate that serum and other tissues can be used as BOS in field conservation programs to monitor wildlife population health. Still, context-specific validations are needed to determine the most appropriate samples to use.

Probing the interaction between niobium pentoxide nanoparticles and serum albumin proteins by Spectroscopic approaches.

Nanoparticles (NPs) can directly or indirectly enter into the body because of their small size; then they tend to alter the conformation and function of proteins upon interaction with them. Thus, it is crucial to understand the impact of NPs in a biological medium. Recently, niobium pentoxide nanoparticles (Nb2O5 NPs) are finding increasing applications in the biological system, for example, bone tissue and dental material, matrix for biosensing of proteins, etc. In all such applications, the Nb2O5 NP interacts with proteins and other biomolecules. Hence, the study of such interactions is of considerable importance. Here in this work, we present the impact of Nb2O5 NP on the structure, stability and activity of blood proteins, bovine serum albumin (BSA) and human serum albumin (HSA) by means of various spectroscopic approaches. Steady-state fluorescence studies indicated that intrinsic fluorescence intensities of both serum albumin proteins got quenched upon their interaction with NP. The nature of the quenching was elucidated by time-resolved fluorescence and absorption measurements. Using circular dichroism (CD) and synchronous fluorescence spectroscopy (SFS), the structural perturbations of the protein molecules after interaction with NP were investigated. Moreover, the role of temperature on protein stability upon complexation with NP was also explored. In addition, the effect of NP on protein functionality was probed by esterase-like activity assays.Communicated by Ramaswamy H. Sarma.

Energy metabolism response induced by microplastic for marine dinoflagellate Karenia mikimotoi.

Microplastic contaminations threaten the entire marine ecosystem and cause severe ecological stress. This study explored the energy metabolism change of Karenia mikimotoi under exposure to nanoplastics (NPs) and microplastics (MPs) (65 nm, 100 nm, and 1 µm polystyrene (PS), and 100 nm polymethyl methacrylate (PMMA)) at a concentration of 10 mg L-1. Membrane potential, esterase activity, polysaccharide content, and ATPase activity were detected to assess the energy metabolism of K. mikimotoi under MPs/NPs exposure. Transcriptome and metabolomic analyses were used to investigate the intrinsic mechanisms of energy metabolism changes. Smaller PS particles caused greater damage to the cell membrane potential, increased the polysaccharide content, and resulted in a heavier weakening of the ATPase enzymatic activity in K. mikimotoi cells, suggesting that smaller-sized PS had more influence on esterase activity and energy metabolism than the bigger-sized PS. The results evidenced that energy metabolism relates to the size and type of MPs/NPs, and nano-scale plastic particles could induce greater metabolic changes.

Interaction of the insecticide bioallethrin with human hemoglobin: biophysical, in silico and enzymatic studies.

Bioallethrin is an insecticide that is widely used in households resulting in human exposure. Bioallethrin is cytotoxic to human erythrocytes. Here we have studied the interaction of bioallethrin with human hemoglobin (Hb) using in silico and biophysical approaches. Incubation of Hb (5 µM) with bioallethrin (1-50 µM) led to increase in absorbance at 280 nm while the Soret band at 406 nm was slightly reduced. The intrinsic fluorescence of Hb was enhanced with the appearance of a new peak around 305 nm. Synchronous fluorescence showed that the binding of bioallethrin to Hb mainly affects the tyrosine microenvironment. The structural changes in Hb were confirmed with a significant shift in CD spectra and about 25% loss of α-helix. Molecular docking and visualisation through Discovery studio confirmed the formation of Hb-bioallethrin complex with a binding energy of -7.3 kcal/mol. Molecular simulation showed the stability and energy dynamics of the binding reaction between bioallethrin and Hb. The structural changes induced by bioallethrin led to inhibition of the esterase activity of Hb. In conclusion, this study shows that bioallethrin forms a stable complex with human Hb which may lead to loss of Hb function in the body.Communicated by Ramaswamy H. Sarma.

Toxicity of Ocimum americanum L. extracts against Aedes aegypti larvae (Diptera: Culicidae) and their impact on insecticide resistance.

Mosquitoes are a key threat to millions of people worldwide. They spread the pathogens that cause deadly diseases among humans and animals. Synthetic pesticides are the best agents to control mosquitoes, but they cause several problems for the environment as well as public health. Continuous usage of commonly available insecticides develops multiple resistances among pests. In search of alternatives to synthetic pesticides, botanicals could be one of the best alternatives to control mosquitoes. The present study explores the insecticidal activity of Ocimum americanum against Aedes aegypti larvae and their effect on detoxification enzymes. Leaves of O. americanum were sequentially extracted using hexane, chloroform, and methanol. Among these, hexane extract showed 100% larvicidal activity at 1 g/L concentration for 24 h and the LC50 value was 0.3 g/L. The phytochemical screening of hexane extract was performed through gas chromatography-mass spectrometry analysis, which showed 27 compounds. The major compounds are squalene (13.03%), camphor (9.77%), and 1-Iodohexadecane (8.02%). The toxicity of active hexane extract was tested against third instar larvae of Chironomus costatus (nontarget organism). Results revealed less toxicity (12.2%) at 1 g/L concentration on the nontarget organism. The enzyme activity of acetylcholinesterase and ß-carboxylesterase was significantly inhibited by the hexane extract. The present study reveals the insecticidal potential of O. americanum with minimum effects on nontarget organisms. The O. americanum extract inhibited the activity of A. aegypti's major insecticide-resistant enzymes. O. americanum could be one of the best alternatives to controlling mosquitoes.

Trachyspermum ammi Bioactives Promote Neuroprotection by Inhibiting Acetylcholinesterase, Aß-Oligomerization/Fibrilization, and Mitigating Oxidative Stress In Vitro.

Neurodegenerative diseases (NDs) are a large category of progressive neurological disorders with diverse clinical and pathological characteristics. Among the NDs, Alzheimer's disease (AD) is the most widespread disease, which affects more than 400 million people globally. Oxidative stress is evident in the pathophysiology of nearly all NDs by affecting several pathways in neurodegeneration. No single drug can manage multi-faceted diseases like NDs. Therefore, an alternative therapeutic strategy is required, which can affect several pathophysiological pathways at a time. To achieve this aim, hexane and ethyl acetate extract from Trachyspermum ammi (Carom) were prepared, and GC/MS identified the bioactive compounds. For the cell-based assays, oxidative stress was induced in SH-SY5Y neuroblastoma cells using hydrogen peroxide to evaluate the neuroprotective potential of the Carom extracts/bioactives. The extracts/bioactives provided neuroprotection in the cells by modulating multiple pathways involved in neurodegeneration, such as alleviating oxidative stress and mitochondrial membrane potential. They were potent inhibitors of acetylcholine esterase enzymes and displayed competitive/mixed-type inhibition. Additionally, anti-Aß1-42 fibrilization/oligomerization and anti-glycation activities were also analyzed. The multi-faceted neuroprotection shown via Carom/Carvacrol makes it a prospective contender in drug development for NDs.

Algicidal characteristics of novel algicidal compounds, cyclic lipopeptide surfactins from Bacillus tequilensis strain D8, in eliminating Heterosigma akashiwo blooms.

Heterosigma akashiwo blooms have caused severe damage to marine ecosystems, the aquaculture industry and human health worldwide. In this study, Bacillus tequilensis D8 isolated from an H. akashiwo bloom area was found to exert high algicidal activity via extracellular metabolite production. This activity remained stable after exposure to different temperatures and light intensities. Scanning electron microscopy observation and fluorescein diacetate staining indicated that the algicidal substances rapidly destroyed algal plasma membranes and decreased esterase activity. Significant decreases in the maximum photochemical quantum yield and relative electron transfer rate were observed, which indicated photosynthetic membrane destruction. Subsequently, the algicidal compounds were separated and purified by high-performance liquid chromatography and identified as three surfactin homologues by interpreting high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy data. Among these, surfactin-C13 and surfactin-C14 exhibited strong algicidal activity against three HAB-causing species, namely, H. akashiwo, Skeletonema costatum, and Prorocentrum donghaiense, with 24 h-LC50 values of 1.2-5.31 µg/ml. Surfactin-C15 showed strong algicidal activity against S. costatum and weak algicidal activity against H. akashiwo but little activity against P. donghaiense. The present study illuminates the algicidal characteristics and mechanisms of action of surfactins on H. akashiwo and their potential applicability in controlling harmful algal blooms.

Assessment of Pharmacological Potential of Novel Exopolysaccharide Isolated from Marine Kocuria sp. Strain AG5: Broad-Spectrum Biological Investigations.

With more than 17 clinically approved Drugs and over 20 prodrugs under clinical investigations, marine bacteria are believed to have a potential supply of innovative therapeutic bioactive compounds. In the current study, Kocuria sp. strain AG5 isolated from the Red Sea was identified and characterized by biochemical and physiological analysis, and examination of a phylogenetic 16S rRNA sequences. Innovative exopolysaccharide (EPS) was separated from the AG5 isolate as a major fraction of EPS (EPSR5, 6.84 g/L-1). The analysis of EPSR5 revealed that EPSR5 has a molecular weight (Mw) of 4.9 × 104 g/mol and number average molecular weight (Mn) of 5.4 × 104 g/mol and contains sulfate (25.6%) and uronic acid (21.77%). Analysis of the monosaccharide composition indicated that the EPSR5 fraction composes of glucose, galacturonic acid, arabinose, and xylose in a molar ratio of 2.0:0.5:0.25:1.0, respectively. Assessment of the pharmacological potency of EPSR5 was explored by examining its cytotoxicity, anti-inflammatory, antioxidant, and anti-acetylcholine esterase influences. The antioxidant effect of EPSR5 was dose- and time-dependently increased and the maximum antioxidant activity (98%) was observed at 2000 µg/mL after 120 min. Further, EPSR5 displayed a significant repressive effect regarding the proliferation of HepG-2, A-549, HCT-116, MCF7, HEP2, and PC3 cells with IC50 453.46 ± 21.8 µg/mL, 873.74 ± 15.4 µg/mL, 788.2 ± 32.6 µg/mL, 1691 ± 44.2 µg/mL, 913.1 ± 38.8 µg/mL, and 876.4 ± 39.8 µg/mL, respectively. Evaluation of the inhibitory activity of the anti-inflammatory activity of EPSR5 indicated that EPSR5 has a significant inhibitory activity toward lipoxygenase (5-LOX) and cyclooxygenase (COX-2) activities (IC50 15.39 ± 0.82 µg/mL and 28.06 ± 1.1 µg/mL, respectively). Finally, ESPR5 presented a substantial hemolysis suppressive action with an IC50 of 65.13 ± 0.89 µg /mL, and a considerable inhibitory activity toward acetylcholine esterase activity (IC50 797.02 µg/mL). Together, this study reveals that secondary metabolites produced by Kocuria sp. strain AG5 marine bacteria serve as an important source of pharmacologically active compounds, and their impact on human health is expected to grow with additional global work and research.