Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 26.419
Filtrar
1.
Phys Chem Chem Phys ; 21(32): 17821-17835, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31373340

RESUMO

The rise of New Delhi metallo-beta-lactamase-1 (NDM-1) producers is a major public health concern due to carbapenem resistance. Infections caused by carbapenem-resistant enterobacteria (CRE) are classified as a serious problem. To understand the structure and function of NDM-1, an amino acid replacement approach is considered as one of the methods to get structural insight. Therefore, we have generated novel mutations (N193A, S217A, G219A and T262A) near active sites and an omega-like loop to study the role of conserved residues of NDM-1. The minimum inhibitory concentrations (MICs) of ampicillin, imipenem, meropenem, cefotaxime, cefoxitin and ceftazidime for all mutants were found to be reduced 2 to 6 fold, compared to a wild type NDM-1 producing strain. The Km values increased while Kcat and Kcat/Km values were decreased compared to wild type. The affinity as well as the catalysis properties of these mutants were reduced considerably for imipenem, meropenem, cefotaxime, cefoxitin, and ceftazidimem compared to wild type, hence the catalytic efficiencies (Kcat/Km) of all mutant enzymes were reduced owing to the poor affinity of the enzyme. The IC50 values of these mutants with respect to each drug were reduced compared to wild type NDM-1. MD simulations and docking results from the mutant protein models, along with the wild type example, showed stable and consistent RMSD, RMSF and Rg behavior. The α-helix content values of all mutant proteins were reduced by 13%, 6%, 14% and 9% compared to NDM-1. Hence, this study revealed the impact role of active sites near residues on the enzyme catalytic activity of NDM-1.


Assuntos
Antibacterianos/química , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , beta-Lactamases/química , Antibacterianos/farmacologia , Biocatálise , Domínio Catalítico , Farmacorresistência Bacteriana , Cinética , Testes de Sensibilidade Microbiana , Mutagênese Sítio-Dirigida , Mutação , Ligação Proteica , Estrutura Secundária de Proteína , Termodinâmica , beta-Lactamases/genética , beta-Lactamases/metabolismo
2.
J Enzyme Inhib Med Chem ; 34(1): 1400-1413, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31401897

RESUMO

A large library of derivatives based on the scaffold of 2-(benzylsulfinyl)benzoic acid were synthesised and tested as atypical inhibitors against four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). The exploration of the chemical space around the main functional groups led to the discovery of selective hCA IX inhibitors in the micromolar/nanomolar range, thus establishing robust structure-activity relationships within this versatile scaffold. HPLC separation of some selected chiral compounds and biological evaluation of the corresponding enantiomers was performed along with molecular modelling studies on the most active derivatives.


Assuntos
Ácido Benzoico/química , Inibidores da Anidrase Carbônica/química , Inibidores da Anidrase Carbônica/farmacologia , Anidrases Carbônicas/efeitos dos fármacos , Desenho de Drogas , Isoenzimas/efeitos dos fármacos , Inibidores da Anidrase Carbônica/síntese química , Domínio Catalítico , Cromatografia Líquida de Alta Pressão , Humanos , Simulação de Acoplamento Molecular , Estereoisomerismo , Relação Estrutura-Atividade
3.
J Agric Food Chem ; 67(31): 8527-8535, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31298526

RESUMO

l-Valine belongs to the branched-chain amino acids (BCAAs) and is an essential amino acid that is crucial for all living organisms. l-Valine is industrially produced by the nonpathogenic bacterium Corynebacterium glutamicum and is synthesized by the BCAA biosynthetic pathway. Ketol-acid reductoisomerase (KARI) is the second enzyme in the BCAA pathway and catalyzes the conversion of (S)-2-acetolactate into (R)-2,3-dihydroxy-isovalerate, or the conversion of (S)-2-aceto-2-hydroxybutyrate into (R)-2,3-dihydroxy-3-methylvalerate. To elucidate the enzymatic properties of KARI from C. glutamicum (CgKARI), we successfully produced CgKARI protein and determined its crystal structure in complex with NADP+ and two Mg2+ ions. Based on the complex structure, docking simulations, and site-directed mutagenesis experiments, we revealed that CgKARI belongs to Class I KARI and identified key residues involved in stabilization of the substrate, metal ions, and cofactor. Furthermore, we confirmed the difference in the binding of metal ions that depended on the conformational change.


Assuntos
Proteínas de Bactérias/química , Corynebacterium glutamicum/enzimologia , Cetol-Ácido Redutoisomerase/química , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Domínio Catalítico , Corynebacterium glutamicum/química , Corynebacterium glutamicum/genética , Cristalografia por Raios X , Cetol-Ácido Redutoisomerase/genética , Cetol-Ácido Redutoisomerase/metabolismo , Metais/química , Metais/metabolismo , Simulação de Acoplamento Molecular , NADP/química , NADP/metabolismo
4.
J Agric Food Chem ; 67(29): 8177-8185, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31290662

RESUMO

Trehalose synthase (TreS) catalyzes the reversible interconversion of maltose to trehalose, and is therefore essential for trehalose production. Consequently, dissecting the catalytic mechanism of TreS is important for enzyme optimization and industrial applications. TreS from Thermobaculum terrenum (TtTreS) is a thermostable enzyme. Here, we studied the composition of the TtTreS active site through computer calculation and enzyme analysis. The results were consistent with a two-step double-displacement mechanism, similar to that of glycoside hydrolase 13 family enzymes. However, our data suggested that glucose rotation, following breakage of the α-1,4 glycosidic bond, is a key factor determining the reaction direction and conversion rate. The N246 residue plays an important role in glucose rotation. Moreover, we established a saturated mutation model for the nonconserved amino acids around the substrate gateway domain. Finally, four TtTreS mutants (K136T, Y137D, K138N, and D139S) resulted in improved trehalose yield compared to that of the wild-type enzyme.


Assuntos
Bactérias/enzimologia , Proteínas de Bactérias/química , Glucosiltransferases/química , Bactérias/química , Bactérias/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Catálise , Domínio Catalítico , Biologia Computacional , Estabilidade Enzimática , Glucosiltransferases/genética , Glucosiltransferases/metabolismo , Temperatura Alta , Especificidade por Substrato
5.
Chemistry ; 25(52): 12145-12158, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31271481

RESUMO

Urease uses a cluster of two NiII ions to activate a water molecule for urea hydrolysis. The key to this unsurpassed enzyme is a change in the conformation of a flexible structural motif, the mobile flap, which must be able to move from an open to a closed conformation to stabilize the chelating interaction of urea with the NiII cluster. This conformational change brings the imidazole side chain functionality of a critical histidine residue, αHis323, in close proximity to the site that holds the transition state structure of the reaction, facilitating its evolution to the products. Herein, we describe the influence of the solution pH in modulating the conformation of the mobile flap. High-resolution crystal structures of urease inhibited in the presence of N-(n-butyl)phosphoric triamide (NBPTO) at pH 6.5 and pH 7.5 are described and compared to the analogous structure obtained at pH 7.0. The kinetics of urease in the absence and presence of NBPTO are investigated by a calorimetric assay in the pH 6.0-8.0 range. The results indicate that pH modulates the protonation state of αHis323, which was revealed to have pKa =6.6, and consequently the conformation of the mobile flap. Two additional residues (αAsp224 and αArg339) are shown to be key factors for the conformational change. The role of pH in modulating the catalysis of urea hydrolysis is clarified through the molecular and structural details of the interplay between protein conformation and solution acidity in the paradigmatic case of a metalloenzyme.


Assuntos
Níquel/química , Urease/química , Amidas/química , Catálise , Domínio Catalítico , Cátions Bivalentes , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Compostos Organofosforados/química , Conformação Proteica , Ureia/química
6.
Chem Biol Interact ; 311: 108746, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31301288

RESUMO

Utilizing food additives at their optimized concentration is believed to be relatively safe, but their combinatorial effects remain largely unexplored. The influence of mixed food additives on the macromolecules may be altered by synergistic or antagonistic effects. It is previously shown that curcumin enhances the catalase activity by affecting its structural pocket in the active site. The aim of this study was to investigate the combination effects of food colorants sunset yellow FCF (SNY) and curcumin on the activation and/or inactivation of catalase activity using multispectral (fluorescence, FTIR, and UV-vis) analysis and simultaneous docking simulations. Kinetic studies demonstrated that SNY could significantly decrease catalase activity through a non-competitive inhibition mechanism. Fluorescence data indicated that SNY reduces intrinsic emission of catalase via a static quenching mechanism. Thermodynamic and molecular docking investigations suggested that catalase has one binding site for SNY, and hydrogen binding plays a main role in the binding reaction of catalase -SNY complex. Molecular dynamic simulation data indicated that the curcumin binding to the cavity, in the middle of the catalase helical domain, facilitates SNY binding to the enzyme pocket. For this purpose, the equilibrium dialysis system was used to study the stability and reversibility of SNY-catalase in the absence or presence of curcumin. The obtained data indicated that the binding of SNY-catalase is reversible and the stability of the complex is time-dependent. However, curcumin could make the complex more stable enhancing the SNY inhibition of catalase activity.


Assuntos
Compostos Azo/química , Catalase/metabolismo , Curcumina/química , Corantes de Alimentos/química , Compostos Azo/metabolismo , Sítios de Ligação , Catalase/antagonistas & inibidores , Domínio Catalítico , Curcumina/metabolismo , Eritrócitos/enzimologia , Corantes de Alimentos/metabolismo , Humanos , Cinética , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Termodinâmica
7.
Nature ; 571(7764): 284-288, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31263273

RESUMO

Hedgehog signalling is fundamental to embryonic development and postnatal tissue regeneration1. Aberrant postnatal Hedgehog signalling leads to several malignancies, including basal cell carcinoma and paediatric medulloblastoma2. Hedgehog proteins bind to and inhibit the transmembrane cholesterol transporter Patched-1 (PTCH1), which permits activation of the seven-transmembrane transducer Smoothened (SMO) via a mechanism that is poorly understood. Here we report the crystal structure of active mouse SMO bound to both the agonist SAG21k and to an intracellular binding nanobody that stabilizes a physiologically relevant active state. Analogous to other G protein-coupled receptors, the activation of SMO is associated with subtle motions in the extracellular domain, and larger intracellular changes. In contrast to recent models3-5, a cholesterol molecule that is critical for SMO activation is bound deep within the seven-transmembrane pocket. We propose that the inactivation of PTCH1 by Hedgehog allows a transmembrane sterol to access this seven-transmembrane site (potentially through a hydrophobic tunnel), which drives the activation of SMO. These results-combined with signalling studies and molecular dynamics simulations-delineate the structural basis for PTCH1-SMO regulation, and suggest a strategy for overcoming clinical resistance to SMO inhibitors.


Assuntos
Membrana Celular/química , Proteínas Hedgehog/agonistas , Transdução de Sinais/efeitos dos fármacos , Receptor Smoothened/agonistas , Receptor Smoothened/metabolismo , Esteróis/farmacologia , Animais , Sítios de Ligação , Técnicas Biossensoriais , Domínio Catalítico/efeitos dos fármacos , Membrana Celular/metabolismo , Colesterol/química , Colesterol/metabolismo , Colesterol/farmacologia , Proteínas Hedgehog/metabolismo , Ligantes , Camundongos , Modelos Moleculares , Simulação de Dinâmica Molecular , Receptor Patched-1/antagonistas & inibidores , Receptor Patched-1/metabolismo , Conformação Proteica , Estabilidade Proteica , Anticorpos de Cadeia Única/imunologia , Receptor Smoothened/antagonistas & inibidores , Receptor Smoothened/química , Esteróis/química , Esteróis/metabolismo , Proteínas de Xenopus/química
8.
Phytochemistry ; 166: 112060, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31302343

RESUMO

Continued interest in bioactive alkaloids led to the isolation of four undescribed alkaloids along with 74 known ones from the aerial parts of Tabernaemontana bufalina Lour. The structures of the yet undescribed alkaloids were elucidated based on NMR, IR, UV, MS and CD spectroscopic data and X-ray crystal diffraction and, according to the plant source, named as taberhaines A-D (1-4). The known compounds comprised of 66 monoterpenoid indole, three carboline and five isoquinoline alkaloids. Among them, the known apparicine inhibited significantly the activity of xanthine oxidase, which plays an important role for gout, with an IC50 value of 0.65 µM, compared to the standard drug allopurinol (IC50 = 0.60 µM).


Assuntos
Alcaloides/química , Alcaloides/farmacologia , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Tabernaemontana/química , Xantina Oxidase/antagonistas & inibidores , Alcaloides/isolamento & purificação , Domínio Catalítico , Inibidores Enzimáticos/isolamento & purificação , Concentração Inibidora 50 , Modelos Moleculares , Xantina Oxidase/química
9.
Chemistry ; 25(51): 11945-11954, 2019 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-31294500

RESUMO

Acyl transferase from Mycobacterium smegmatis (MsAcT) is a promising biocatalyst because it catalyzes an acyl transfer reaction in aqueous solution, thereby accepting many primary and secondary alcohols as substrates. MsAcT also exhibits high enantioselectivity for a selected number of secondary alcohols. To increase the applicability of this enzyme for the production of optically active compounds, a detailed understanding of the reaction mechanism and the factors that affect enantioselectivity is essential. Herein, quantum chemical calculations are employed to study the reactions of two secondary alcohols, 1-isopropyl propargyl alcohol and 2-hydroxy propanenitrile, for which the enzyme displays opposite enantiopreference, favoring the S enantiomer in the former case and R enantiomer in the latter. A model of the active site has been designed and for both substrates various binding modes are evaluated and the intermediates and transition states along the reaction path are then located. The calculated energy profiles agree with the experimental observations, and reproduce the selectivity outcome. Through a detailed analysis of the geometries of key transition states, insights into the origins of the enantiopreference are obtained.


Assuntos
Álcoois/química , Mycobacterium smegmatis/química , Transferases/metabolismo , Catálise , Domínio Catalítico , Estereoisomerismo
10.
Chemistry ; 25(51): 11837-11841, 2019 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-31310409

RESUMO

Bacterial production of ß-lactamases with carbapenemase activity is a global health threat. The active sites of class D carbapenemases such as OXA-48, which is of major clinical importance, uniquely contain a carbamylated lysine residue which is essential for catalysis. Although there is significant interest in characterizing this post-translational modification, and it is a promising inhibition target, protein carbamylation is challenging to monitor in solution. We report the use of 19 F NMR spectroscopy to monitor the carbamylation state of 19 F-labelled OXA-48. This method was used to investigate the interactions of OXA-48 with clinically used serine ß-lactamase inhibitors, including avibactam and vaborbactam. Crystallographic studies on 19 F-labelled OXA-48 provide a structural rationale for the sensitivity of the 19 F label to active site interactions. The overall results demonstrate the use of 19 F NMR to monitor reversible covalent post-translational modifications.


Assuntos
Compostos Azabicíclicos/química , Proteínas de Bactérias/química , Radioisótopos de Flúor/química , Inibidores de beta-Lactamases/farmacologia , beta-Lactamases/farmacologia , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Espectroscopia de Ressonância Magnética , Carbamilação de Proteínas , Processamento de Proteína Pós-Traducional , Inibidores de beta-Lactamases/química , beta-Lactamases/química , beta-Lactamases/metabolismo
11.
Biochemistry (Mosc) ; 84(4): 407-415, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31228932

RESUMO

Proton-translocating FOF1-ATP synthase (F-type ATPase, F-ATPase or FOF1) performs ATP synthesis/hydrolysis coupled to proton transport across the membrane in mitochondria, chloroplasts, and most eubacteria. The ATPase activity of the enzyme is suppressed in the absence of protonmotive force by several regulatory mechanisms. The most conserved of these mechanisms is noncompetitive inhibition of ATP hydrolysis by the MgADP complex (ADP-inhibition) which has been found in all the enzymes studied. When MgADP binds without phosphate in the catalytic site, the enzyme enters an inactive state, and MgADP gets locked in the catalytic site and does not exchange with the medium. The degree of ADP-inhibition varies in FOF1 enzymes from different organisms. In the Escherichia coli enzyme, ADP-inhibition is relatively weak and, in contrast to other organisms, is enhanced rather than suppressed by phosphate. In this study, we used site-directed mutagenesis to investigate the role of amino acid residues ß139, ß158, ß189, and ß319 of E. coli FOF1-ATP synthase in the mechanism of ADP-inhibition and its modulation by the protonmotive force. The amino acid residues in these positions differ in the enzymes from beta- and gammaproteobacteria (including E. coli) and FOF1-ATP synthases from other eubacteria, mitochondria, and chloroplasts. The ßN158L substitution produced no effect on the enzyme activity, while substitutions ßF139Y, ßF189L, and ßV319T only slightly affected ATP (1 mM) hydrolysis. However, in a mixture of ATP and ADP, the activity of the mutants was less suppressed than that of the wild-type enzyme. In addition, mutations ßF189L and ßV319T weakened the ATPase activity inhibition by phosphate in the presence of ADP. We suggest that residues ß139, ß189, and ß319 are involved in the mechanism of ADP-inhibition and its modulation by phosphate.


Assuntos
Difosfato de Adenosina/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/enzimologia , ATPases Translocadoras de Prótons/metabolismo , Difosfato de Adenosina/química , Trifosfato de Adenosina/metabolismo , Sequência de Aminoácidos , Domínio Catalítico , Proteínas de Escherichia coli/antagonistas & inibidores , Proteínas de Escherichia coli/genética , Cinética , Mutagênese Sítio-Dirigida , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Força Próton-Motriz , ATPases Translocadoras de Prótons/antagonistas & inibidores , ATPases Translocadoras de Prótons/genética , Alinhamento de Sequência
12.
Chem Pharm Bull (Tokyo) ; 67(6): 556-565, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31155561

RESUMO

Aldose reductase (AR) is associated with the onset of diabetic complications. Botryllazine A and its analogues were synthesized and evaluated for human AR inhibitory activity. Analogues possessing aromatic bicyclic systems at the C5 position of the central pyrazine ring exhibited superior AR inhibiting activity relative to the parent botryllazine A. In addition, the benzoyl groups at positions C2 and C3 of the pyrazine ring were dispensable for this improved inhibitory activity. Conversely, a benzoyl group-containing phenolic hydroxyl groups-at either position C2 or C3 of the pyrazine ring was essential for attainment of high inhibitory activity approaching that of sorbinil (a highly effective AR inhibitor).


Assuntos
Aldeído Redutase/metabolismo , Inibidores Enzimáticos/síntese química , Pirazinas/química , Aldeído Redutase/antagonistas & inibidores , Sítios de Ligação , Domínio Catalítico , Cristalografia por Raios X , Inibidores Enzimáticos/química , Inibidores Enzimáticos/metabolismo , Humanos , Ligações de Hidrogênio , Concentração Inibidora 50 , Conformação Molecular , Simulação de Acoplamento Molecular , Pirazinas/síntese química , Pirazinas/metabolismo
13.
Chem Pharm Bull (Tokyo) ; 67(6): 599-603, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31155566

RESUMO

The PF-543 is known as a potent and selective inhibitor of sphingosine kinase (SK) 1 amongst all the SK inhibitors known to date. In a recently reported study by Pfizer on the synthesis of PF-543 derivatives and the SK inhibitory effects, the introduction of propyl moiety into sulfonyl group of PF-543 in the case of 26b revealed an excellent result of 1.7 nM of IC50 of SK1, suggesting the potential substitution of chain structure for benzenesulfonyl structure. In the present work, we aimed for identification of antitumor activity and inhibitory effects of PF-543 derivative containing aliphatic long chain (similar to known SK inhibitors) on SK1. The synthesized compound 2 exhibited an inhibitory effect on SK1 in a manner similar to that of PF-543; the PF-543 derivative manifested similar antitumor activity on HT29, HCT116 (colorectal cancer cell line), and AGS (gastric cancer cell line) cells. Also, from the docking study conducted with PF-543 and compound 2, it was apparent that the aliphatic chain in compound 2 could probably replace benzenesulfonyl structure of PF-543.


Assuntos
Antineoplásicos/síntese química , Pirrolidinas/química , Sulfonas/química , Antineoplásicos/química , Antineoplásicos/farmacologia , Sítios de Ligação , Domínio Catalítico , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Humanos , Concentração Inibidora 50 , Simulação de Acoplamento Molecular , Fosfotransferases (Aceptor do Grupo Álcool)/antagonistas & inibidores , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Pirrolidinas/síntese química , Pirrolidinas/farmacologia , Relação Estrutura-Atividade , Sulfonas/síntese química , Sulfonas/farmacologia
14.
Acta Crystallogr D Struct Biol ; 75(Pt 6): 564-577, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31205019

RESUMO

Several pathogenic bacteria utilize sialic acid, including host-derived N-acetylneuraminic acid (Neu5Ac), in at least two ways: they use it as a nutrient source and as a host-evasion strategy by coating themselves with Neu5Ac. Given the significant role of sialic acid in pathogenesis and host-gut colonization by various pathogenic bacteria, including Neisseria meningitidis, Haemophilus influenzae, Pasteurella multocida and Vibrio cholerae, several enzymes of the sialic acid catabolic, biosynthetic and incorporation pathways are considered to be potential drug targets. In this work, findings on the structural and functional characterization of CMP-N-acetylneuraminate synthetase (CMAS), a key enzyme in the incorporation pathway, from Vibrio cholerae are reported. CMAS catalyzes the synthesis of CMP-sialic acid by utilizing CTP and sialic acid. Crystal structures of the apo and the CDP-bound forms of the enzyme were determined, which allowed the identification of the metal cofactor Mg2+ in the active site interacting with CDP and the invariant Asp215 residue. While open and closed structural forms of the enzyme from eukaryotic and other bacterial species have already been characterized, a partially closed structure of V. cholerae CMAS (VcCMAS) observed upon CDP binding, representing an intermediate state, is reported here. The kinetic data suggest that VcCMAS is capable of activating the two most common sialic acid derivatives, Neu5Ac and Neu5Gc. Amino-acid sequence and structural comparison of the active site of VcCMAS with those of eukaryotic and other bacterial counterparts reveal a diverse hydrophobic pocket that interacts with the C5 substituents of sialic acid. Analyses of the thermodynamic signatures obtained from the binding of the nucleotide (CTP) and the product (CMP-sialic acid) to VcCMAS provide fundamental information on the energetics of the binding process.


Assuntos
Proteínas de Bactérias/química , N-Acilneuraminato Citidililtransferase/química , Vibrio cholerae/enzimologia , Sequência de Aminoácidos , Proteínas de Bactérias/farmacologia , Proteínas de Bactérias/fisiologia , Sítios de Ligação , Domínio Catalítico , Cristalização , Cristalografia por Raios X/métodos , Cistina Difosfato/química , Cistina Difosfato/metabolismo , Ácido N-Acetilneuramínico Citidina Monofosfato/química , Ácido N-Acetilneuramínico Citidina Monofosfato/metabolismo , Citidina Trifosfato/química , Citidina Trifosfato/metabolismo , N-Acilneuraminato Citidililtransferase/farmacologia , N-Acilneuraminato Citidililtransferase/fisiologia , Domínios e Motivos de Interação entre Proteínas , Estrutura Quaternária de Proteína , Ácidos Siálicos/metabolismo
15.
Phys Chem Chem Phys ; 21(25): 13545-13554, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31172995

RESUMO

Human aldehyde oxidase (hAOX1) is a molybdenum dependent enzyme that plays an important role in the metabolism of various compounds either endogenous or xenobiotics. Due to its promiscuity, hAOX1 plays a major role in the pharmacokinetics of many drugs and therefore has gathered a lot of attention from the scientific community and, particularly, from the pharmaceutical industry. In this work, homology modelling, molecular docking and molecular dynamics simulations were used to study the structure of the monomer and dimer of human AOX. The results with the monomer of hAOX1 allowed to shed some light on the role played by thioridazine and two malonate ions that are co-crystalized in the recent X-ray structure of hAOX1. The results show that these molecules endorse several conformational rearrangements in the binding pocket of the enzyme and these changes have an impact in the active site topology as well as in the stability of the substrate (phthalazine). The results show that the presence of both molecules open two gates located at the entrance of the binding pocket, from which results the flooding of the active site. They also endorse several modifications in the shape of the binding pocket (namely the position of Lys893) that, together with the presence of the solvent molecules, favour the release of the substrate to the solvent. Further insights were also obtained with the assembled homodimer of hAOX1. The allosteric inhibitor (THI) binds closely to the region where the dimerization of both monomers occur. These findings suggest that THI can interfere with protein dimerization.


Assuntos
Aldeído Oxidase/química , Domínio Catalítico , Cristalização , Humanos , Cinética , Malonatos/química , Modelos Moleculares , Ftalazinas/química , Ligação Proteica , Conformação Proteica , Multimerização Proteica , Solventes , Tioridazina/química
16.
Phys Chem Chem Phys ; 21(25): 13578-13589, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31173012

RESUMO

Donepezil, an acetylcholinesterase inhibitor, is an approved drug for the symptomatic treatment of Alzheimer's disease (AD). The mechanistic pathway for the inhibition mechanism of acetylcholinesterase (AChE) by donepezil is not well explored. We report for the first time, the inhibition mechanism of AChE by the donepezil drug molecule for the hydrolysis of acetylcholine (ACh) with docking and well-tempered metadynamics (WTMtD) simulations with a human acetylcholinesterase (hAChE) crystal structure (). This study explored the orientation of the donepezil drug molecule inside the gorge of AChE. The 1D free energy surface obtained from WTMtD simulation studies reveals that the orientation of donepezil in the crystal donepezil (-87.25 kJ mol-1) is energetically more favored than the other orientation of donepezil (-74.74 kJ mol-1) for inhibition of AChE. The free energy landscape computation for the two sets of CVs further corroborates the 1D free energy surface. The WTMtD simulation performed with the crystal structure of donepezil bound hAChE gives the conformation of donepezil at Basin-I as similar to the conformation of donepezil observed in the crystal structure (). The WTMtD simulations further reveal that the bridged water molecules are more ordered near the catalytic triad of AChE to deter the nucleophilicity of Ser203 through intermolecular hydrogen bonding when donepezil approaches near to the active site gorge of AChE. The presence of donepezil near the active site of AChE can inhibit its approach for ACh hydrolysis; this is revealed through the docking study, where the drug molecule inside the active gorge of hAChE restricts the approach of ACh to Ser203 for the hydrolysis process.


Assuntos
Doença de Alzheimer/tratamento farmacológico , Inibidores da Colinesterase/farmacologia , Donepezila/farmacologia , Modelos Moleculares , Acetilcolinesterase/química , Catálise , Domínio Catalítico , Inibidores da Colinesterase/química , Cristalização , Donepezila/química , Humanos , Ligações de Hidrogênio , Hidrólise , Ligação Proteica , Termodinâmica
17.
Chem Biol Interact ; 308: 339-349, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31170387

RESUMO

Magnolol, the most abundant bioactive constituent of the Chinese herb Magnolia officinalis, has been found with multiple biological activities, including anti-oxidative, anti-inflammatory and enzyme-regulatory activities. In this study, the inhibitory effects and inhibition mechanism of magnolol on human carboxylesterases (hCEs), the key enzymes responsible for the hydrolytic metabolism of a variety of endogenous esters as well as ester-bearing drugs, have been well-investigated. The results demonstrate that magnolol strongly inhibits hCE1-mediated hydrolysis of various substrates, whereas the inhibition of hCE2 by magnolol is substrate-dependent, ranging from strong to moderate. Inhibition of intracellular hCE1 and hCE2 by magnolol was also investigated in living HepG2 cells, and the results showed that magnolol could strongly inhibit intracellular hCE1, while the inhibition of intracellular hCE2 was weak. Inhibition kinetic analyses and docking simulations revealed that magnolol inhibited both hCE1 and hCE2 in a mixed manner, which could be partially attributed to its binding at two distinct ligand-binding sites in each carboxylesterase, including the catalytic cavity and the regulatory domain. In addition, the potential risk of the metabolic interactions of magnolol via hCE1 inhibition was predicted on the basis of a series of available pharmacokinetic data and the inhibition constants. All these findings are very helpful in deciphering the metabolic interactions between magnolol and hCEs, and also very useful for avoiding deleterious interactions via inhibition of hCEs.


Assuntos
Compostos de Bifenilo/metabolismo , Hidrolases de Éster Carboxílico/metabolismo , Lignanas/metabolismo , Sítios de Ligação , Biocatálise , Compostos de Bifenilo/química , Hidrolases de Éster Carboxílico/antagonistas & inibidores , Domínio Catalítico , Medicamentos de Ervas Chinesas/química , Medicamentos de Ervas Chinesas/metabolismo , Células Hep G2 , Humanos , Hidrólise , Cinética , Lignanas/química , Simulação de Acoplamento Molecular
18.
Chem Biol Interact ; 308: 323-331, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31173750

RESUMO

Organophosphorus compounds have been widely employed to the development of warfare nerve agents and pesticides, resulting in a huge number of people intoxicated annually, being a serious problem of public health. Efforts worldwide have been done in order to design new technologies that are capable of combating or even reversing the poisoning caused by these OP nerve agents. In this line, the bioremediation arises as a promising and efficient alternative for this purpose. As an example of degrading enzymes, there is the organophosphate-degrading (OpdA) enzyme from Agrobacterium radiobacter, which has been quite investigated experimentally due to its high performance in the degradation of neurotoxic nerve agents. This work aims to look into the structural and electronic details that govern the interaction modes of these compounds in the OpdA active site, with the posterior hydrolysis reaction prediction. Our findings have brought about data about the OpdA performance towards different nerve agents, and among them, we may realize that the degradation efficiency strongly depends on the nerve agent structure and its stereochemistry, being in this case the compound Tabun the one more effectively hydrolyzed. By means of the chemical bonds (AIM) and orbitals (FERMO) analysis, it is suggested that the initial reactivity of the OP nerve agents in the OpdA active site does not necessarily dictate the reactivity and interaction modes over the reaction coordinate.


Assuntos
Biodegradação Ambiental , Agentes Neurotóxicos/metabolismo , Agrobacterium tumefaciens/enzimologia , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Biocatálise , Domínio Catalítico , Humanos , Simulação de Acoplamento Molecular , Agentes Neurotóxicos/química , Monoéster Fosfórico Hidrolases/química , Monoéster Fosfórico Hidrolases/metabolismo , Teoria Quântica , Sarina/química , Sarina/metabolismo
19.
Chem Biol Interact ; 308: 350-356, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31173753

RESUMO

Activation of human butyrylcholinesterase by small quaternary ammonium ions is known. Here, additional ligands in this series are presented: edrophonium and choline, and the reactivator pyridine-2-aldoxime methochloride. Kinetic analysis of the progress curves with these compounds indicates the mechanism of enhanced deacylation by the ligand bound to the catalytic anionic site (Trp82) at the base of the active site. The larger, bis-quaternary ligands examined, as propidium, hexamethonium, decamethonium, and bis-thiocholine, show only competitive inhibition of butyrylcholinesterase, by preventing substrate approach. This hypothesis of enhanced deacylation was tested for reactivation of methanesulfonylfluoride-inactivated butyrylcholinesterase, a complex analogous to organophosphate-aged cholinesterases. The combination of substrate/products and pyridine-2-aldoxime methochloride improved butyrylcholinesterase activity over 2 h of continuous measurements, before which time substrate depletion prevailed. Similar reactivation of Torpedo californica acetylcholinesterase was unsuccessful, but both of these cholinesterases regain some activity if they have been inhibited and aged for days by diisopropylfluorophosphate.


Assuntos
Butirilcolinesterase/metabolismo , Inibidores da Colinesterase/metabolismo , Oximas/metabolismo , Butirilcolinesterase/química , Domínio Catalítico , Colina/química , Colina/metabolismo , Inibidores da Colinesterase/química , Edrofônio/química , Edrofônio/metabolismo , Humanos , Cinética , Ligantes , Oximas/química , Especificidade por Substrato
20.
Chem Biol Interact ; 308: 392-395, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31175846

RESUMO

Carbamates are esters of substituted carbamic acids that react with acetylcholinesterase (AChE) by initially transferring the carbamoyl group to a serine residue in the enzyme active site accompanied by loss of the carbamate leaving group followed by hydrolysis of the carbamoyl enzyme. This hydrolysis, or decarbamoylation, is relatively slow, and half-lives of carbamoylated AChEs range from 4 min to more than 30 days. Therefore, carbamates are effective AChE inhibitors that have been developed as insecticides and as therapeutic agents. In this report, we review recent data showing that decarbamoylation rate constants are independent of the ester leaving group for a series of carbamic acid esters with the same carbamoyl group and that decarbamoylation rate constants decreased by 800-fold when the alkyl substituents on the carbamoyl group increased in size from N-monomethyl- to N,N-diethyl-. We also review data showing that solvent deuterium oxide isotope effects for decarbamoylation decreased from 2.8 for N-monomethylcarbamoyl AChE to 1.1 for N,N-diethylcarbamoyl AChE, indicating a shift in the rate-limiting step from general acid-base catalysis to a likely conformational change in the distorted active site in N,N-diethylcarbamoyl AChE. The nature of such a conformational change is suggested from X-ray crystal structures of AChE phosphorylated by paraoxon.


Assuntos
Acetilcolinesterase/metabolismo , Carbamatos/metabolismo , Acetilcolinesterase/química , Carbamatos/química , Domínio Catalítico , Cristalografia por Raios X , Cinética , Paraoxon/química , Paraoxon/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA