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Bowling PE, Dasgupta S, Herbert JM. Eliminating Imaginary Vibrational Frequencies in Quantum-Chemical Cluster Models of Enzymatic Active Sites. J Chem Inf Model 2024; 64:3912-3922. [PMID: 38648614 DOI: 10.1021/acs.jcim.4c00221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
In constructing finite models of enzyme active sites for quantum-chemical calculations, atoms at the periphery of the model must be constrained to prevent unphysical rearrangements during geometry relaxation. A simple fixed-atom or "coordinate-lock" approach is commonly employed but leads to undesirable artifacts in the form of small imaginary frequencies. These preclude evaluation of finite-temperature free-energy corrections, limiting thermochemical calculations to enthalpies only. Full-dimensional vibrational frequency calculations are possible by replacing the fixed-atom constraints with harmonic confining potentials. Here, we compare that approach to an alternative strategy in which fixed-atom contributions to the Hessian are simply omitted. While the latter strategy does eliminate imaginary frequencies, it tends to underestimate both the zero-point energy and the vibrational entropy while introducing artificial rigidity. Harmonic confining potentials eliminate imaginary frequencies and provide a flexible means to construct active-site models that can be used in unconstrained geometry relaxations, affording better convergence of reaction energies and barrier heights with respect to the model size, as compared to models with fixed-atom constraints.
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Affiliation(s)
- Paige E Bowling
- Biophysics Graduate Program, The Ohio State University, Columbus, Ohio 43210, United States
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Saswata Dasgupta
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
- Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla, California 92093, United States
| | - John M Herbert
- Biophysics Graduate Program, The Ohio State University, Columbus, Ohio 43210, United States
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
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2
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Dos Santos Nascimento IJ, Albino SL, da Silva Menezes KJ, de Azevedo Teotônio Cavalcanti M, de Oliveira MS, Mali SN, de Moura RO. Targeting SmCB1: Perspectives and Insights to Design Antischistosomal Drugs. Curr Med Chem 2024; 31:2264-2284. [PMID: 37921174 DOI: 10.2174/0109298673255826231011114249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 09/01/2023] [Accepted: 09/14/2023] [Indexed: 11/04/2023]
Abstract
Neglected tropical diseases (NTDs) are prevalent in tropical and subtropical countries, and schistosomiasis is among the most relevant diseases worldwide. In addition, one of the two biggest problems in developing drugs against this disease is related to drug resistance, which promotes the demand to develop new drug candidates for this purpose. Thus, one of the drug targets most explored, Schistosoma mansoni Cathepsin B1 (SmCB1 or Sm31), provides new opportunities in drug development due to its essential functions for the parasite's survival. In this way, here, the latest developments in drug design studies targeting SmCB1 were approached, focusing on the most promising analogs of nitrile, vinyl sulphones, and peptidomimetics. Thus, it was shown that despite being a disease known since ancient times, it remains prevalent throughout the world, with high mortality rates. The therapeutic arsenal of antischistosomal drugs (ASD) consists only of praziquantel, which is widely used for this purpose and has several advantages, such as efficacy and safety. However, it has limitations, such as the impossibility of acting on the immature worm and exploring new targets to overcome these limitations. SmCB1 shows its potential as a cysteine protease with a catalytic triad consisting of Cys100, His270, and Asn290. Thus, design studies of new inhibitors focus on their catalytic mechanism for designing new analogs. In fact, nitrile and sulfonamide analogs show the most significant potential in drug development, showing that these chemical groups can be better exploited in drug discovery against schistosomiasis. We hope this manuscript guides the authors in searching for promising new antischistosomal drugs.
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Affiliation(s)
- Igor José Dos Santos Nascimento
- Pharmacy Department, Cesmac University Center, Maceió, 57051-160, Brazil
- Laboratório de Desenvolvimento e Síntese de Fármacos, Departamento de Farmácia, Universidade Estadual da Paraíba, Campina Grande 58429-500, Brazil
- Programa de Pós Graduação em Ciências Farmacêuticas, Universidade Estadual da Paraíba, Campina Grande, 58429-500, Brazil
| | - Sonaly Lima Albino
- Laboratório de Desenvolvimento e Síntese de Fármacos, Departamento de Farmácia, Universidade Estadual da Paraíba, Campina Grande 58429-500, Brazil
| | - Karla Joane da Silva Menezes
- Laboratório de Desenvolvimento e Síntese de Fármacos, Departamento de Farmácia, Universidade Estadual da Paraíba, Campina Grande 58429-500, Brazil
- Programa de Pós Graduação em Ciências Farmacêuticas, Universidade Estadual da Paraíba, Campina Grande, 58429-500, Brazil
| | - Misael de Azevedo Teotônio Cavalcanti
- Laboratório de Desenvolvimento e Síntese de Fármacos, Departamento de Farmácia, Universidade Estadual da Paraíba, Campina Grande 58429-500, Brazil
- Programa de Pós Graduação em Ciências Farmacêuticas, Universidade Estadual da Paraíba, Campina Grande, 58429-500, Brazil
| | - Mozaniel Santana de Oliveira
- Coordination of Botany-Laboratory Adolpho Ducke, Avenida Perimetral, Museu Paraense Emílio Goeldi, 1901, Belém, 66077-530, PA Brazil
| | - Suraj N Mali
- Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, Matunga East, Mumbai, 400019, India
| | - Ricardo Olimpio de Moura
- Laboratório de Desenvolvimento e Síntese de Fármacos, Departamento de Farmácia, Universidade Estadual da Paraíba, Campina Grande 58429-500, Brazil
- Programa de Pós Graduação em Ciências Farmacêuticas, Universidade Estadual da Paraíba, Campina Grande, 58429-500, Brazil
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3
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Zaman N, Azam SS. Discrete Dynamics of Warhead Modulation on Covalent Inhibition of Oxyr: A QM/MM Study. J Phys Chem B 2023. [PMID: 37377002 DOI: 10.1021/acs.jpcb.2c07376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
The bacterial transcriptional factor OxyR, a peroxide sensor conserved in bacterial virulence pathways, has the capability to exhibit exceptional reactivity toward hydrogen peroxide (H2O2). H2O2 is essential for oxidizing cysteine thiolates to maintain cellular redox homeostasis and is dispensable for bacterial growth that can potentially mitigate drug resistance, thus underlining OxyR as a valuable target. We employ quantum mechanics/molecular mechanics (QM/MM) umbrella sampling (US) simulations at the DFTB3/MM level of theory and propose a reaction mechanism with four potential covalent inhibitors. The potential of mean force reveals the direct role of intrinsic reactivity of inhibitors, for instance, benzothiophenes and modified experimental inhibitors with methyl oxo-enoate warhead-activated carbonyl samples in the first step of reaction, which shed light on the significance of proton transfer indispensable for full inhibition, whereas the nitrile inhibitor undergoes a stepwise mechanism with a small proton-transfer energy barrier and lower imaginary frequencies that materialize instantly after nucleophilic attack. To unveil the molecular determinants of respective binding affinities, transition states along the reaction path are optimized and characterized with B3LYP 6-31+G(d,p). Furthermore, the post-simulation analysis indicates the catalytic triad (His130/Cys199/Thr129), thermodynamically favored for inhibition, which restricts water molecules from acting as the potential source of protonation/deprotonation. This study thus serves as a preamble to add variation in the proposed structures and unveils the impact of functional groups lying in warheads that modulate the kinetics of proton transfer, which will certainly aid to design more selective and efficient irreversible inhibitors of OxyR.
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Affiliation(s)
- Naila Zaman
- Computational Biology Lab, National Center for Bioinformatics, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | - Syed Sikander Azam
- Computational Biology Lab, National Center for Bioinformatics, Quaid-i-Azam University, Islamabad 45320, Pakistan
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4
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Ng R, Zhang G, Li JJ. An update on the discovery and development of reversible covalent inhibitors. Med Chem Res 2023; 32:1039-1062. [PMID: 37305209 PMCID: PMC10148018 DOI: 10.1007/s00044-023-03065-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 04/18/2023] [Indexed: 06/13/2023]
Abstract
Small molecule drugs that covalently bind irreversibly to their target proteins have several advantages over conventional reversible inhibitors. They include increased duration of action, less-frequent drug dosing, reduced pharmacokinetic sensitivity, and the potential to target intractable shallow binding sites. Despite these advantages, the key challenges of irreversible covalent drugs are their potential for off-target toxicities and immunogenicity risks. Incorporating reversibility into covalent drugs would lead to less off-target toxicity by forming reversible adducts with off-target proteins and thus reducing the risk of idiosyncratic toxicities caused by the permanent modification of proteins, which leads to higher levels of potential haptens. Herein, we systematically review electrophilic warheads employed during the development of reversible covalent drugs. We hope the structural insights of electrophilic warheads would provide helpful information to medicinal chemists and aid in designing covalent drugs with better on-target selectivity and improved safety. Graphical Abstract
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Affiliation(s)
- Raymond Ng
- Olema Oncology, 512 2nd St., 4th Floor, San Francisco, 94107 CA USA
| | - Guiping Zhang
- Genhouse Bio, No.1 Xinze Road, Suzhou Industrial Park, Suzhou, Jiangsu Province 215123 PR China
| | - Jie Jack Li
- Genhouse Bio, No.1 Xinze Road, Suzhou Industrial Park, Suzhou, Jiangsu Province 215123 PR China
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5
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Behring L, Ruiz-Gómez G, Trapp C, Morales M, Wodtke R, Köckerling M, Kopka K, Pisabarro MT, Pietzsch J, Löser R. Dipeptide-Derived Alkynes as Potent and Selective Irreversible Inhibitors of Cysteine Cathepsins. J Med Chem 2023; 66:3818-3851. [PMID: 36867428 PMCID: PMC10041539 DOI: 10.1021/acs.jmedchem.2c01360] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
The potential of designing irreversible alkyne-based inhibitors of cysteine cathepsins by isoelectronic replacement in reversibly acting potent peptide nitriles was explored. The synthesis of the dipeptide alkynes was developed with special emphasis on stereochemically homogeneous products obtained in the Gilbert-Seyferth homologation for C≡C bond formation. Twenty-three dipeptide alkynes and 12 analogous nitriles were synthesized and investigated for their inhibition of cathepsins B, L, S, and K. Numerous combinations of residues at positions P1 and P2 as well as terminal acyl groups allowed for the derivation of extensive structure-activity relationships, which were rationalized by computational covalent docking for selected examples. The determined inactivation constants of the alkynes at the target enzymes span a range of >3 orders of magnitude (3-10 133 M-1 s-1). Notably, the selectivity profiles of alkynes do not necessarily reflect those of the nitriles. Inhibitory activity at the cellular level was demonstrated for selected compounds.
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Affiliation(s)
- Lydia Behring
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
- Technische Universität Dresden, School of Science, Faculty of Chemistry and Food Chemistry, Mommsenstraße 4, 01069 Dresden, Germany
| | - Gloria Ruiz-Gómez
- BIOTEC, Technische Universität Dresden, Tatzberg 47-51, 01307 Dresden, Germany
| | - Christian Trapp
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Maryann Morales
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Robert Wodtke
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Martin Köckerling
- Institute of Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany
| | - Klaus Kopka
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
- Technische Universität Dresden, School of Science, Faculty of Chemistry and Food Chemistry, Mommsenstraße 4, 01069 Dresden, Germany
| | - M Teresa Pisabarro
- BIOTEC, Technische Universität Dresden, Tatzberg 47-51, 01307 Dresden, Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
- Technische Universität Dresden, School of Science, Faculty of Chemistry and Food Chemistry, Mommsenstraße 4, 01069 Dresden, Germany
| | - Reik Löser
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany
- Technische Universität Dresden, School of Science, Faculty of Chemistry and Food Chemistry, Mommsenstraße 4, 01069 Dresden, Germany
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6
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Meanwell NA. The pyridazine heterocycle in molecular recognition and drug discovery. Med Chem Res 2023; 32:1-69. [PMID: 37362319 PMCID: PMC10015555 DOI: 10.1007/s00044-023-03035-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Accepted: 02/06/2023] [Indexed: 03/17/2023]
Abstract
The pyridazine ring is endowed with unique physicochemical properties, characterized by weak basicity, a high dipole moment that subtends π-π stacking interactions and robust, dual hydrogen-bonding capacity that can be of importance in drug-target interactions. These properties contribute to unique applications in molecular recognition while the inherent polarity, low cytochrome P450 inhibitory effects and potential to reduce interaction of a molecule with the cardiac hERG potassium channel add additional value in drug discovery and development. The recent approvals of the gonadotropin-releasing hormone receptor antagonist relugolix (24) and the allosteric tyrosine kinase 2 inhibitor deucravacitinib (25) represent the first examples of FDA-approved drugs that incorporate a pyridazine ring. In this review, the properties of the pyridazine ring are summarized in comparison to the other azines and its potential in drug discovery is illustrated through vignettes that explore applications that take advantage of the inherent physicochemical properties as an approach to solving challenges associated with candidate optimization. Graphical Abstract
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7
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Kang M, Park SG, Lee SA, Kim S, Lee D, Shirbhate ME, Youn SY, Kim KM, Cha SS, Kwon J. Targeting BAP1 with small compound inhibitor for colon cancer treatment. Sci Rep 2023; 13:2264. [PMID: 36754982 PMCID: PMC9908887 DOI: 10.1038/s41598-023-29017-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 01/30/2023] [Indexed: 02/10/2023] Open
Abstract
BRCA1-associated protein-1 (BAP1) is a ubiquitin C-terminal hydrolase domain-containing deubiquitinase. The gene encoding BAP1 is mutated in various human cancers, including mesothelioma, uveal melanoma and renal cell carcinoma. BAP1 plays roles in many cancer-related cellular functions, including cell proliferation, cell death, and nuclear processes crucial for genome stability, such as DNA repair and replication. While these findings suggest that BAP1 functions as a tumor suppressor, recent data also suggest that BAP1 might play tumor-promoting roles in certain cancers, such as breast cancer and hematopoietic malignancies. Here, we show that BAP1 is upregulated in colon cancer cells and tissues and that BAP1 depletion reduces colon cancer cell proliferation and tumor growth. BAP1 contributes to colon cancer cell proliferation by accelerating DNA replication and suppressing replication stress and concomitant apoptosis. A recently identified BAP1 inhibitor, TG2-179-1, which seems to covalently bind to the active site of BAP1, exhibits potent cytotoxic activity against colon cancer cells, with half-maximal inhibitory concentrations of less than 10 μM, and inhibits colon tumor growth. TG2-179-1 exerts cytotoxic activity by targeting BAP1, leading to defective replication and increased apoptosis. This work therefore shows that BAP1 acts oncogenically in colon cancer and is a potential therapeutic target for this cancer. Our work also suggests that TG2-179-1 can be developed as a potential therapeutic agent for colon cancer.
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Affiliation(s)
- Minhwa Kang
- Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Seul Gi Park
- Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Shin-Ai Lee
- Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea.,Laboratory of Genitourinary Cancer Pathogenesis, Center for Cancer Research, National Cancer Institute, Building 37, Room 1068, MD, 20892-4263, Bethesda, USA
| | - Soyi Kim
- Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Daye Lee
- Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Mukesh Eknath Shirbhate
- Department of Chemistry and Nanoscience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - So-Yeon Youn
- Department of Chemistry and Nanoscience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Kwan Mook Kim
- Department of Chemistry and Nanoscience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Sun-Shin Cha
- Department of Chemistry and Nanoscience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea
| | - Jongbum Kwon
- Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Korea.
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8
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Kim H, Hauner D, Laureanti JA, Agustin K, Raugei S, Kumar N. Mechanistic investigation of SARS-CoV-2 main protease to accelerate design of covalent inhibitors. Sci Rep 2022; 12:21037. [PMID: 36470873 PMCID: PMC9722715 DOI: 10.1038/s41598-022-23570-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 11/02/2022] [Indexed: 12/12/2022] Open
Abstract
Targeted covalent inhibition represents one possible strategy to block the function of SARS-CoV-2 Main Protease (MPRO), an enzyme that plays a critical role in the replication of the novel SARS-CoV-2. Toward the design of covalent inhibitors, we built a covalent inhibitor dataset using deep learning models followed by high throughput virtual screening of these candidates against MPRO. Two top-ranking inhibitors were selected for mechanistic investigations-one with an activated ester warhead that has a piperazine core and the other with an acrylamide warhead. Specifically, we performed a detailed analysis of the free energetics of covalent inhibition by hybrid quantum mechanics/molecular mechanics simulations. Cleavage of a fragment of the non-structured protein (NSP) from the SARS-CoV-2 genome was also simulated for reference. Simulations show that both candidates form more stable enzyme-inhibitor (E-I) complexes than the chosen NSP. It was found that both the NSP fragment and the activated ester inhibitor react with CYS145 of MPRO in a concerted manner, whereas the acrylamide inhibitor follows a stepwise mechanism. Most importantly, the reversible reaction and the subsequent hydrolysis reaction from E-I complexes are less probable when compared to the reactions with an NSP fragment, showing promise for these candidates to be the base for efficient MPRO inhibitors.
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Affiliation(s)
- Hoshin Kim
- grid.451303.00000 0001 2218 3491Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352 USA
| | - Darin Hauner
- grid.451303.00000 0001 2218 3491Earth and Biological Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352 USA
| | - Joseph A. Laureanti
- grid.451303.00000 0001 2218 3491Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352 USA
| | - Kruel Agustin
- grid.451303.00000 0001 2218 3491Earth and Biological Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352 USA
| | - Simone Raugei
- grid.451303.00000 0001 2218 3491Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352 USA
| | - Neeraj Kumar
- grid.451303.00000 0001 2218 3491Earth and Biological Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352 USA
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Parise A, Romeo I, Russo N, Marino T. The Se-S Bond Formation in the Covalent Inhibition Mechanism of SARS-CoV-2 Main Protease by Ebselen-like Inhibitors: A Computational Study. Int J Mol Sci 2021; 22:9792. [PMID: 34575955 PMCID: PMC8467846 DOI: 10.3390/ijms22189792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/03/2021] [Accepted: 09/07/2021] [Indexed: 12/20/2022] Open
Abstract
The inhibition mechanism of the main protease (Mpro) of SARS-CoV-2 by ebselen (EBS) and its analog with a hydroxyl group at position 2 of the benzisoselenazol-3(2H)-one ring (EBS-OH) was studied by using a density functional level of theory. Preliminary molecular dynamics simulations on the apo form of Mpro were performed taking into account both the hydrogen donor and acceptor natures of the Nδ and Nε of His41, a member of the catalytic dyad. The potential energy surfaces for the formation of the Se-S covalent bond mediated by EBS and EBS-OH on Mpro are discussed in detail. The EBS-OH shows a distinctive behavior with respect to EBS in the formation of the noncovalent complex. Due to the presence of canonical H-bonds and noncanonical ones involving less electronegative atoms, such as sulfur and selenium, the influence on the energy barriers and reaction energy of the Minnesota hybrid meta-GGA functionals M06, M06-2X and M08HX, and the more recent range-separated hybrid functional wB97X were also considered. The knowledge of the inhibition mechanism of Mpro by the small protease inhibitors EBS or EBS-OH can enlarge the possibilities for designing more potent and selective inhibitor-based drugs to be used in combination with other antiviral therapies.
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Affiliation(s)
- Angela Parise
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, CS, Italy; (A.P.); (I.R.); (N.R.)
- Institut de Chimie Physique UMR8000, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Isabella Romeo
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, CS, Italy; (A.P.); (I.R.); (N.R.)
| | - Nino Russo
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, CS, Italy; (A.P.); (I.R.); (N.R.)
| | - Tiziana Marino
- Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, CS, Italy; (A.P.); (I.R.); (N.R.)
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10
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A Nut for Every Bolt: Subunit-Selective Inhibitors of the Immunoproteasome and Their Therapeutic Potential. Cells 2021; 10:cells10081929. [PMID: 34440698 PMCID: PMC8394499 DOI: 10.3390/cells10081929] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/21/2021] [Accepted: 07/26/2021] [Indexed: 12/15/2022] Open
Abstract
At the heart of the ubiquitin-proteasome system, the 20S proteasome core particle (CP) breaks down the majority of intracellular proteins tagged for destruction. Thereby, the CP controls many cellular processes including cell cycle progression and cell signalling. Inhibitors of the CP can suppress these essential biological pathways, resulting in cytotoxicity, an effect that is beneficial for the treatment of certain blood cancer patients. During the last decade, several preclinical studies demonstrated that selective inhibition of the immunoproteasome (iCP), one of several CP variants in mammals, suppresses autoimmune diseases without inducing toxic side effects. These promising findings led to the identification of natural and synthetic iCP inhibitors with distinct chemical structures, varying potency and subunit selectivity. This review presents the most prominent iCP inhibitors with respect to possible scientific and medicinal applications, and discloses recent trends towards pan-immunoproteasome reactive inhibitors that cumulated in phase II clinical trials of the lead compound KZR-616 for chronic inflammations.
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11
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Banerjee S. An insight into the interaction between α-ketoamide- based inhibitor and coronavirus main protease: A detailed in silico study. Biophys Chem 2021; 269:106510. [PMID: 33285430 PMCID: PMC7695570 DOI: 10.1016/j.bpc.2020.106510] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 11/20/2020] [Accepted: 11/23/2020] [Indexed: 02/07/2023]
Abstract
The search for therapeutic drugs that can neutralize the effects of COVID-2019 (SARS-CoV-2) infection is the main focus of current research. The coronavirus main protease (Mpro) is an attractive target for anti-coronavirus drug design. Further, α-ketoamide is proved to be very effective as a reversible covalent-inhibitor against cysteine proteases. Herein, we report on the non-covalent to the covalent adduct formation mechanism of α-ketoamide-based inhibitor with the enzyme active site amino acids by QM/SQM model (QM = quantum mechanical, SQM = semi-empirical QM). To uncover the mechanism, we focused on two approaches: a concerted and a stepwise fashion. The concerted pathway proceeds via deprotonation of the thiol of cysteine (here, Cys145 SγH) and simultaneous reversible nucleophilic attack of sulfur onto the α-ketoamide warhead. In this work, we propose three plausible concerted pathways. On the contrary, in a traditional two-stage pathway, the first step is proton transfer from Cys145 SγH to His41 Nδ forming an ion pair, and consecutively, in the second step, the thiolate ion attacks the α-keto group to form a thiohemiketal. In this reaction, we find that the stability of the tetrahedral intermediate oxyanion/hydroxyl group plays an important role. Moreover, as the α-keto group has two faces Si or Re for the nucleophilic attack, we considered both possibilities of attack leading to S- and R-thiohemiketal. We computed the structural, electronic, and energetic parameters of all stationary points including transition states via ONIOM and pure DFT method. Additionally, to characterize covalent, weak noncovalent interaction (NCI) and hydrogen-bonds, we applied NCI-reduced density gradient (NCI-RDG) methods along with Bader's Quantum Theory of Atoms-in-Molecules (QTAIM) and natural bonding orbital (NBO) analysis.
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Affiliation(s)
- Snehasis Banerjee
- Department of Chemistry, Government College of Engineering and Leather Technology, Salt Lake, Sector-3, Kolkata, PIN-700106, West Bengal, India.
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12
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Jílková A, Horn M, Fanfrlík J, Küppers J, Pachl P, Řezáčová P, Lepšík M, Fajtová P, Rubešová P, Chanová M, Caffrey CR, Gütschow M, Mareš M. Azanitrile Inhibitors of the SmCB1 Protease Target Are Lethal to Schistosoma mansoni: Structural and Mechanistic Insights into Chemotype Reactivity. ACS Infect Dis 2021; 7:189-201. [PMID: 33301315 PMCID: PMC7802074 DOI: 10.1021/acsinfecdis.0c00644] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
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Azapeptide
nitriles are postulated to reversibly covalently react
with the active-site cysteine residue of cysteine proteases and form
isothiosemicarbazide adducts. We investigated the interaction of azadipeptide
nitriles with the cathepsin B1 drug target (SmCB1) from Schistosoma
mansoni, a pathogen that causes the global neglected disease
schistosomiasis. Azadipeptide nitriles were superior inhibitors of
SmCB1 over their parent carba analogs. We determined the crystal structure
of SmCB1 in complex with an azadipeptide nitrile and analyzed the
reaction mechanism using quantum chemical calculations. The data demonstrate
that azadipeptide nitriles, in contrast to their carba counterparts,
undergo a change from E- to Z-configuration
upon binding, which gives rise to a highly favorable energy profile
of noncovalent and covalent complex formation. Finally, azadipeptide
nitriles were considerably more lethal than their carba analogs against
the schistosome pathogen in culture, supporting the further development
of this chemotype as a treatment for schistosomiasis.
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Affiliation(s)
- Adéla Jílková
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Martin Horn
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Jindřich Fanfrlík
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Jim Küppers
- Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
| | - Petr Pachl
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Pavlína Řezáčová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Martin Lepšík
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Pavla Fajtová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Petra Rubešová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
| | - Marta Chanová
- Institute of Immunology and Microbiology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Studničkova 2028/7, 12800 Prague 2, Czech Republic
| | - Conor R. Caffrey
- Center for Discovery and Innovation in Parasitic Diseases (CDIPD), Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States
| | - Michael Gütschow
- Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany
| | - Michael Mareš
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo n. 2, 16610 Prague 6, Czech Republic
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13
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Oanca G, Asadi M, Saha A, Ramachandran B, Warshel A. Exploring the Catalytic Reaction of Cysteine Proteases. J Phys Chem B 2020; 124:11349-11356. [PMID: 33264018 DOI: 10.1021/acs.jpcb.0c08192] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cysteine proteases play a major role in many life processes and are the target of key drugs. The reaction mechanism of these enzymes is a complex process, which involves several steps that are divided into two main groups: acylation and deacylation. In this work, we studied the energy profile for the acylation and a part of the deacylation reaction of three different enzymes, cruzain, papain, and the Q19A-mutated papain with the benzyloxycarbonyl-phenylalanylarginine-4-methylcoumaryl-7-amide (CBZ-FR-AMC) substrate. The calculations were performed using the EVB and PDLD/S-LRA methods. The overall agreement between the calculated and observed results is encouraging and indicates that we captured the correct reaction mechanism. Finally, our finding indicates that the minimum of the reaction profile, between the acylation and deacylation steps, should provide an excellent state for the binding of covalent inhibitors.
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Affiliation(s)
- Gabriel Oanca
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
| | - Mojgan Asadi
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
| | - Arjun Saha
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
| | - Balajee Ramachandran
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States.,Structural Biology and Bio-computing Lab, Department of Bioinformatics, Alagappa University, Karaikudi, Tamil Nadu 630 004, India
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
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14
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Mechanistic insights into the inhibition mechanism of cysteine cathepsins by chalcone-based inhibitors—a QM cluster model approach. Struct Chem 2019. [DOI: 10.1007/s11224-018-1273-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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15
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Quesne MG, Silveri F, de Leeuw NH, Catlow CRA. Advances in Sustainable Catalysis: A Computational Perspective. Front Chem 2019; 7:182. [PMID: 31032245 PMCID: PMC6473102 DOI: 10.3389/fchem.2019.00182] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 03/07/2019] [Indexed: 11/13/2022] Open
Abstract
The enormous challenge of moving our societies to a more sustainable future offers several exciting opportunities for computational chemists. The first principles approach to "catalysis by design" will enable new and much greener chemical routes to produce vital fuels and fine chemicals. This prospective outlines a wide variety of case studies to underscore how the use of theoretical techniques, from QM/MM to unrestricted DFT and periodic boundary conditions, can be applied to biocatalysis and to both homogeneous and heterogenous catalysts of all sizes and morphologies to provide invaluable insights into the reaction mechanisms they catalyze.
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16
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Dos Santos AM, Cianni L, De Vita D, Rosini F, Leitão A, Laughton CA, Lameira J, Montanari CA. Experimental study and computational modelling of cruzain cysteine protease inhibition by dipeptidyl nitriles. Phys Chem Chem Phys 2019; 20:24317-24328. [PMID: 30211406 DOI: 10.1039/c8cp03320j] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chagas disease affects millions of people in Latin America. This disease is caused by the protozoan parasite Trypanossoma cruzi. The cysteine protease cruzain is a key enzyme for the survival and propagation of this parasite lifecycle. Nitrile-based inhibitors are efficient inhibitors of cruzain that bind by forming a covalent bond with this enzyme. Here, three nitrile-based inhibitors dubbed Neq0409, Neq0410 and Neq0570 were synthesized, and the thermodynamic profile of the bimolecular interaction with cruzain was determined using isothermal titration calorimetry (ITC). The result suggests the inhibition process is enthalpy driven, with a detrimental contribution of entropy. In addition, we have used hybrid Quantum Mechanical/Molecular Mechanical (QM/MM) and Molecular Dynamics (MD) simulations to investigate the reaction mechanism of reversible covalent modification of cruzain by Neq0409, Neq0410 and Neq0570. The computed free energy profile shows that the nucleophilic attack of Cys25 on the carbon C1 of inhibitiors and the proton transfer from His162 to N1 of the dipeptidyl nitrile inhibitor take place in a single step. The calculated free energy of the inhibiton reaction is in agreement with covalent experimental binding. Altogether, the results reported here suggests that nitrile-based inhibitors are good candidates for the development of reversible covalent inhibitors of cruzain and other cysteine proteases.
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Affiliation(s)
- Alberto Monteiro Dos Santos
- Laboratório de Planejamento e Desenvolvimento de Fármacos, Universidade Federal do Pará, Cidade Universitária Prof. José da Silveira Netto, Rua Augusto Correa S/N, Belém-PA, Brazil.
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17
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Ca2+ binding induced sequential allosteric activation of sortase A: An example for ion-triggered conformational selection. PLoS One 2018; 13:e0205057. [PMID: 30321208 PMCID: PMC6188747 DOI: 10.1371/journal.pone.0205057] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 09/19/2018] [Indexed: 12/11/2022] Open
Abstract
The allosteric activation of the intrinsically disordered enzyme Staphylococcus aureus sortase A is initiated via binding of a Ca2+ ion. Although Ca2+ binding was shown to initiate structural changes inducing disorder-to-order transitions, the details of the allosteric activation mechanism remain elusive. We performed long-term molecular dynamics simulations of sortase A without (3 simulations of 1.6 μs) and with bound Ca2+ (simulations of 1.6 μs, 1.8 μs, and 2.5 μs). Our results show that Ca2+ binding causes not only ordering of the disordered β6/β7 loop of the protein, but also modulates hinge motions in the dynamic β7/β8 loop, which is important for the catalytic activity of the enzyme. Cation binding triggers signal transmission from the Ca2+ binding site to the dynamic β7/β8 loop via the repetitive folding/unfolding of short helical stretches of the disordered β6/β7 loop. These correlated structural rearrangements lead to several distinct conformational states of the binding groove, which show optimal binding features for the sorting signal motif and feature binding energies up to 20 kcal/mol more favorable than observed for the sortase A without Ca2+. The presented results indicate a highly correlated, conformational selection-based activation mechanism of the enzyme triggered by cation binding. They also demonstrate the importance of the dynamics of intrinsically disordered regions for allosteric regulation.
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18
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Patel A, Tiwari S, Jha PK. Density functional theory based probe of the affinity interaction of saccharide ligands with extra-cellular sialic acid residues. J Biomol Struct Dyn 2018; 37:1545-1554. [PMID: 29624120 DOI: 10.1080/07391102.2018.1461690] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Changes in glycosylation pattern leads to malignant transformations among the cells. In combination with upregulated actions of sialyltransferases, it ultimately leads to differential expression of sialic acid (SA) at cell surface. Given its negative charge and localization to extracellular domain, SA has been exploited for the development of targeted theranostics using approaches, such as, cationization and appending recognition saccharides on carrier surface. In this study, we have performed quantum mechanical calculations based on density functional theory (DFT) to study the interaction of saccharides with extracellular SA. Gradient-corrected DFT with the three parameter function (B3) was utilized for the calculation of Lee-Yang-Parr (LYP) correlation function. Atomic charge, vibrational frequencies and energy of the optimized structures were calculated through B3LYP. Our calculations demonstrate a stronger galactose-sialic acid interaction at tumour-relevant low pH and hyperthermic condition. These results support the application of pH responsive delivery vehicles and targeted hyperthermic chemotherapy for eradicating solid tumour deposits. These studies, conducted a priori, can guide the formulation scientists over appropriate choice of ligands and their applications in the design of 'smart' theranostic tools.
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Key Words
- AChE, Acetylcholine Esterase
- ASDase, aspartate semialdehyde dehydrogenase
- B3LYP, Becke 3-Parameter Lee, Yang and Parr
- BACE1, Beta-secretase 1
- BSSE, basis set superposition error
- CK2, casein kinase 2
- CMAS, cytidine monophosphate N-acetylneuraminic acid synthase
- DFT, density functional theory
- EcPLA, Echis carinatus Phospholipase A
- FF, fukui function
- GSK3β, glycogen synthase kinase 3β
- Gal, galactose
- HLG, HOMO-LUMO gap
- HOMO, highest occupied molecular orbital
- LUMO, lowest unoccupied molecular orbital
- MEP, molecular electrostatic potential
- Man, mannose
- NBO, natural bond orbital
- NC, nanocarriers.
- PBA, phenylboronic acid
- SA, sialic acid
- cancer
- density functional theory
- hypersialylation
- recognition saccharides
- targeted theranostics
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Affiliation(s)
- Anjali Patel
- a Department of Physics, Faculty of Science , The Maharaja Sayajirao University of Baroda , Vadodara - 390 002 , India
| | - Sanjay Tiwari
- b Maliba Pharmacy College , UKA Tarsadia University, Gopal-Vidyanagar Campus , Surat , 394350 , India
| | - Prafulla K Jha
- a Department of Physics, Faculty of Science , The Maharaja Sayajirao University of Baroda , Vadodara - 390 002 , India
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19
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Pitchumani Violet Mary C, Shankar R, Vijayakumar S. Theoretical studies on the interaction between the nitrile-based inhibitors and the catalytic triad of Cathepsin K. J Biomol Struct Dyn 2017; 36:634-655. [PMID: 28150528 DOI: 10.1080/07391102.2017.1289863] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Computational studies on the interaction of novel inhibitor compounds with the Cathepsin K protease have been performed to study the inhibition properties of the inhibitor compounds. The quantum chemical calculations have been performed to analyze the molecular geometries, structural stability, reactivity, nature of interaction, and the charge transfer properties using B3LYP level of theory by implementing 6-311g(d,p) basis set. The calculated C-S and N-H…N bond lengths of the inhibitor-triad complexes are found to agree well with the previous literature results. The chemical reactivity of the inhibitors and catalytic triad are analyzed through frontier molecular orbital analysis and found that the inhibitors are subjected to nucleophilic attack by the catalytic triad. The nature of inhibition of the inhibitor compounds is examined using the quantum theory of Atoms in Molecules analysis and found to be partially covalent. The NBO stabilization energy for the Cys - inhibitor are found to be most stable than the other interactions. The molecular dynamic simulations were performed to study the influence of dynamic of the active site on the QM results. The many body decomposition interaction energy calculated for the final results of MD simulation reveals that the dynamic of the active site induces significant changes in the interaction energy and occupancy of H-bonds plays a major role in the stabilizing the active site inhibitor interactions. The present study reveals that the inhibitor compounds can inhibit the proteolytic activity of the proteases on binding with the catalytic active site.
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Affiliation(s)
| | - R Shankar
- a Department of Physics , Bharathiar University , Coimbatore 641 046 , India
| | - S Vijayakumar
- b Department of Medical Physics , Bharathiar University , Coimbatore 641 046 , India
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20
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Si L, Li P, Liu X, Luo L. Chinese herb medicine against Sortase A catalyzed transformations, a key role in gram-positive bacterial infection progress. J Enzyme Inhib Med Chem 2016; 31:184-196. [PMID: 27162091 DOI: 10.1080/14756366.2016.1178639] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Many Gram-positive bacteria can anchor their surface proteins to the cell wall peptidoglycan covalently by a common mechanism with Sortase A (SrtA), thus escaping from the host's identification of immune cells. SrtA can complete this anchoring process by cleaving LPXTG motif conserved among these surface proteins and thus these proteins anchor on the cell wall. Moreover, those SrtA mutants lose this capability to anchor these relative proteins, with these bacteria no longer infectious. Therefore, SrtA inhibitors can be promising anti-infective agents to cure bacterial infections. Chinese herb medicines (CHMs) (chosen from Science Citation Index) have exhibited inhibition on SrtA of Gram-positive pathogens irreversibly or reversibly. In general, CHMs are likely to have important long-term impact as new antibacterial compounds and sought after by academia and the pharmaceutical industry. This review mainly focuses on SrtA inhibitors from CHMs and the potential inhibiting mechanism related to chemical structures of compounds in CHMs.
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Affiliation(s)
- Lifang Si
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Pan Li
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Xiong Liu
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Lixin Luo
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
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Omotuyi OI. Methyl-methoxylpyrrolinone and flavinium nucleus binding signatures on falcipain-2 active site. J Mol Model 2014; 20:2386. [PMID: 25096811 DOI: 10.1007/s00894-014-2386-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 07/17/2014] [Indexed: 01/18/2023]
Abstract
Following the increasing reports of human toxicity and plasmodium resistance to artemisinin and its derivatives, falcipain-2 (FP-2) is now emerging as the choice antimalarial drug target. Coincidentally, FP-2 is the in vivo target of naturally occurring, therapeutically safe flavonoids (stenopalustroside, myricetin, and fisetin) and symplostatin (symplostatin 4) compounds known to exhibit potent in vitro and in vivo antiplasmodial actions. Here, the structural bases for their inhibitory actions have been studied using molecular dynamics simulation. Myricetin and fisetin act as proton transfer tunnel breakers by inserting between His174 and Cys42, which are key active site residues of FP-2, stenopalustroside inhibits the polarization of His174 by Asn173; a major preparatory step for Cys42/His174 proton transfer process. The roles of flavonoids are favored by T-shaped pi-pi interactions with His174. Symplostatin 4 inserts its methyl-methoxylpyrrolinone moiety into the active site where its proton acceptor function prepares Cys42 for nucleophilic attack on the Michael α,β-unsaturated bonds on its 4(S)-amino-2(E)-pentenoate moiety. Further analyses of the structures identified a unique bridge formed on FP-2 active site groove by stenopalustroside and symplostatin 4 during interaction with the sub-site I of FP-2, whereas fisetin preferentially interacts with sub-site II and myricetin interacts with sub-site III residues. Ultimately, symplostatin-4, myricetin, and fisetin were better than stenopalustroside at trapping FP-2 in its inactive state as revealed by comparative RSMD plots with X-ray structures of FP-2 co-crystallized with inhibitors. Comparative estimates of free energy of binding using the Molecular Mechanics-Poisson Boltzmann Surface Area (MMPBSA) method suggested that His174 protonation may further enhance stenopalustroside-FP-2 interaction. The unique binding signatures of the ligands within the FP-2 active site groove and its sub-sites may explain the subtle differences in their IC50 values and their mechanism of inhibition.
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Affiliation(s)
- Olaposi I Omotuyi
- Center for Drug Discovery and Therapeutic Innovation, Nagasaki University, Nagasaki, Japan,
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