RESUMO
The oximes 4-carbamoyl-1-[({2-[(E)-(hydroxyimino) methyl] pyridinium-1-yl} methoxy) methyl] pyridinium (known as HI-6) and 3-carbamoyl-1-[({2-[(E)-(hydroxyimino) methyl] pyridinium-1-yl} methoxy) methyl] pyridinium (known as HS-6) are isomers differing from each other only by the position of the carbamoyl group on the pyridine ring. However, this slight difference was verified to be responsible for big differences in the percentual of reactivation of acetylcholinesterase (AChE) inhibited by the nerve agents tabun, sarin, cyclosarin, and VX. In order to try to find out the reason for this, a computational study involving molecular docking, molecular dynamics, and binding energies calculations, was performed on the binding modes of HI-6 and HS-6 on human AChE (HssAChE) inhibited by those nerve agents.
Assuntos
Acetilcolinesterase/metabolismo , Substâncias para a Guerra Química/química , Inibidores da Colinesterase/química , Agentes Neurotóxicos/química , Oximas/metabolismo , Compostos de Pralidoxima/metabolismo , Compostos de Piridínio/metabolismo , Humanos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Organofosfatos/química , Compostos Organofosforados/química , Compostos Organotiofosforados/química , Sarina/químicaRESUMO
Neurotoxic organophosphorus compounds (OPs), which are used as pesticides and chemical warfare agents lead to more than 700,000 intoxications worldwide every year. The main target of OPs is the inhibition of acetylcholinesterase (AChE), an enzyme necessary for the control of the neurotransmitter acetylcholine (ACh). The control of ACh function is performed by its hydrolysis with AChE, a process that can be completely interrupted by inhibition of the enzyme by phosphylation with OPs. Compounds used for reactivation of the phosphylated AChE are cationic oximes, which usually possess low membrane and hematoencephalic barrier permeation. Neutral oximes possess a better capacity for hematoencephalic barrier permeation. NMR spectroscopy is a very confident method for monitoring the inhibition and reactivation of enzymes, different from the Ellman test, which is the common method for evaluation of inhibition and reactivation of AChE. In this work (1)H NMR was used to test the effect of neutral oximes on inhibition of AChE and reactivation of AChE inhibited with ethyl-paraoxon. The results confirmed that NMR is a very efficient method for monitoring the action of AChE, showing that neutral oximes, which display a significant AChE inhibition activity, are potential drugs for Alzheimer disease. The NMR method showed that a neutral oxime, previously indicated by the Ellman test as better in vitro reactivator of AChE inhibited with paraoxon than pralidoxime (2-PAM), was much less efficient than 2-PAM, confirming that NMR is a better method than the Ellman test.
Assuntos
Acetilcolinesterase/metabolismo , Inibidores da Colinesterase/metabolismo , Reativadores da Colinesterase/metabolismo , Electrophorus/metabolismo , Oximas/metabolismo , Acetilcolinesterase/química , Animais , Inibidores da Colinesterase/química , Reativadores da Colinesterase/química , Espectroscopia de Ressonância Magnética , Oximas/química , Paraoxon/análogos & derivados , Paraoxon/metabolismo , FosforilaçãoRESUMO
We have applied a theoretical methodology, previously developed to evaluate the association and kinetic reactivation constants of oximes, comparing theoretical data obtained for human acetylcholinesterase (HsAChE) with in vitro results from Mus musculus AChE (MmAChE) previously reported in the literature. Our results, further checked by additional molecular dynamics simulations steps, showed a good correlation between the theoretical and experimental data, supporting the methodology as appropriate for prediction of thermodynamic and kinetic parameters and corroborated MmAChE as a suitable model for studies with HsAChE.
Assuntos
Acetilcolinesterase/metabolismo , Reativadores da Colinesterase/metabolismo , Oximas/metabolismo , Acetilcolinesterase/química , Sequência de Aminoácidos , Animais , Inibidores da Colinesterase/metabolismo , Humanos , Cinética , Camundongos , Modelos Moleculares , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Dados de Sequência Molecular , Oximas/química , Alinhamento de Sequência , Relação Estrutura-Atividade , TermodinâmicaRESUMO
In this work a theoretical methodology for evaluation of the association and kinetic reactivation constants of oximes using the Molegro and Spartan softwares was proposed and validated facing in vitro data previously reported in the literature. Results showed a very good agreement between the theoretical binding free energies of the reactivators and experimental data, suggesting that the proposed methodology could work well in the prediction of kinetic and thermodynamics parameters for oximes that might be helpful for the design and selection of new and more effective oximes.
Assuntos
Acetilcolinesterase/metabolismo , Reativadores da Colinesterase/farmacologia , Descoberta de Drogas/métodos , Ativação Enzimática/efeitos dos fármacos , Modelos Moleculares , Acetilcolinesterase/química , Animais , Domínio Catalítico , Inibidores da Colinesterase/farmacologia , Reativadores da Colinesterase/metabolismo , Camundongos , Organofosfatos/farmacologia , Oximas/metabolismo , Oximas/farmacologia , Teoria Quântica , TermodinâmicaRESUMO
In this work a theoretical methodology for evaluation of the association and kinetic reactivation constants of oximes using the Molegro and Spartan softwares was proposed and validated facing in vitro data previously reported in the literature. Results showed a very good agreement between the theoretical binding free energies of the reactivators and experimental data, suggesting that the proposed methodology could work well in the prediction of kinetic and thermodynamics parameters for oximes that might be helpful for the design and selection of new and more effective oximes.
Assuntos
Acetilcolinesterase/metabolismo , Reativadores da Colinesterase/farmacologia , Descoberta de Drogas/métodos , Ativação Enzimática/efeitos dos fármacos , Modelos Moleculares , Acetilcolinesterase/química , Animais , Domínio Catalítico , Inibidores da Colinesterase/farmacologia , Reativadores da Colinesterase/metabolismo , Camundongos , Organofosfatos/farmacologia , Oximas/metabolismo , Oximas/farmacologia , Teoria Quântica , TermodinâmicaRESUMO
The transformation of organic halogenated pesticides by laccase-mediator system has been investigated. Twelve pesticides were assayed in the presence of nine different mediators. Acetosyringone and syringaldehyde showed to be the best mediators. The halogenated pesticides bromoxynil, niclosamide, bromofenoxim and dichlorophen were transformed by the laccase-syringaldehyde system showing catalytic activities of 48.8, 142.0, 166.2 and 1257.6nmolmin(-1)U(-1), respectively. The highest pesticide transformation rates were obtained with a mediator-substrate proportion of 5:1, one of the lowest reported so far for the laccase-mediator systems. The analysis of the main product from the dichlorophen transformation showed that an oxidative dehalogenation is involved in the catalytic mechanism. Adduct formation between the mediator syringaldehyde and the pesticides dichlorophen or bromoxynil was also found after enzymatic oxidation. The main goal of this work is to evaluate environmental-friendly mediators for the pesticide transformation, and the potential of laccase-mediator system to efficiently reduce the environmental impact of organic halogenated pesticides is discussed.
Assuntos
Fungos/enzimologia , Lacase/metabolismo , Praguicidas/metabolismo , Benzaldeídos/metabolismo , Biotransformação , Diclorofeno/química , Diclorofeno/metabolismo , Halogenação , Niclosamida/química , Niclosamida/metabolismo , Nitrilas/química , Nitrilas/metabolismo , Oxirredução , Oximas/química , Oximas/metabolismo , Praguicidas/química , Trametes/enzimologiaRESUMO
O-glycoprotein 2-acetamino-2-deoxy-beta- d-glucopyranosidase ( O-GlcNAcase) hydrolyzes 2-acetamido-2-deoxy-beta- d-glucopyranose ( O-GlcNAc) residues of serine/threonine residues of modified proteins. O-GlcNAc is present in many intracellular proteins and appears to have a role in the etiology of several diseases including cancer, Alzheimer's disease, and type II diabetes. In this work, we have carried out molecular dynamics simulations using a hybrid quantum mechanics/molecular mechanics approach to determine the binding of two potent inhibitors, PUGNAc and NAG, with a bacterial O-GlcNAcase. The results of these simulations show that Asp-401, Asp-298, and Asp-297 residues play an important role in the protein-inhibitor interactions. These results might be useful to design compounds with more interesting inhibitory activity on the basis of its three-dimensional structure.