1
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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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Jedrzejewski M, Belza B, Lewandowska I, Sadlej M, Perlinska AP, Augustyniak R, Christian T, Hou YM, Kalek M, Sulkowska JI. Nucleolar Essential Protein 1 (Nep1): Elucidation of enzymatic catalysis mechanism by molecular dynamics simulation and quantum mechanics study. Comput Struct Biotechnol J 2023; 21:3999-4008. [PMID: 37649713 PMCID: PMC10462857 DOI: 10.1016/j.csbj.2023.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/01/2023] [Accepted: 08/01/2023] [Indexed: 09/01/2023] Open
Abstract
The Nep1 protein is essential for the formation of eukaryotic and archaeal small ribosomal subunits, and it catalyzes the site-directed SAM-dependent methylation of pseudouridine (Ψ) during pre-rRNA processing. It possesses a non-trivial topology, namely, a 31 knot in the active site. Here, we address the issue of seemingly unfeasible deprotonation of Ψ in Nep1 active site by a distant aspartate residue (D101 in S. cerevisiae), using a combination of bioinformatics, computational, and experimental methods. We identified a conserved hydroxyl-containing amino acid (S233 in S. cerevisiae, T198 in A. fulgidus) that may act as a proton-transfer mediator. Molecular dynamics simulations, based on the crystal structure of S. cerevisiae, and on a complex generated by molecular docking in A. fulgidus, confirmed that this amino acid can shuttle protons, however, a water molecule in the active site may also serve this role. Quantum-chemical calculations based on density functional theory and the cluster approach showed that the water-mediated pathway is the most favorable for catalysis. Experimental kinetic and mutational studies reinforce the requirement for the aspartate D101, but not S233. These findings provide insight into the catalytic mechanisms underlying proton transfer over extended distances and comprehensively elucidate the mode of action of Nep1.
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Affiliation(s)
- Mateusz Jedrzejewski
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Barbara Belza
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Iwona Lewandowska
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Marta Sadlej
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Agata P. Perlinska
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Rafal Augustyniak
- Department of Chemistry, University of Warsaw, Ludwika Pasteura 1, 02-093, Warsaw, Poland
| | - Thomas Christian
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 4201 Henry Ave, Philadelphia, PA 19144, USA
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 4201 Henry Ave, Philadelphia, PA 19144, USA
| | - Marcin Kalek
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
| | - Joanna I. Sulkowska
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097, Warsaw, Poland
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3
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Mahmoodi N, Minnow YVT, Harijan RK, Bedard GT, Schramm VL. Cell-Effective Transition-State Analogue of Phenylethanolamine N-Methyltransferase. Biochemistry 2023; 62:2257-2268. [PMID: 37467463 PMCID: PMC10646973 DOI: 10.1021/acs.biochem.3c00103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Phenylethanolamine N-methyltransferase (PNMT) catalyzes the S-adenosyl-l-methionine (SAM)-dependent methylation of norepinephrine to form epinephrine. Epinephrine is implicated in the regulation of blood pressure, respiration, Alzheimer's disease, and post-traumatic stress disorder (PTSD). Transition-state (TS) analogues bind their target enzymes orders of magnitude more tightly than their substrates. A synthetic strategy for first-generation TS analogues of human PNMT (hPNMT) permitted structural analysis of hPNMT and revealed potential for second-generation inhibitors [Mahmoodi, N.; J. Am. Chem. Soc. 2020, 142, 14222-14233]. A second-generation TS analogue inhibitor of PNMT was designed, synthesized, and characterized to yield a Ki value of 1.2 nM. PNMT isothermal titration calorimetry (ITC) measurements of inhibitor 4 indicated a negative cooperative binding mechanism driven by large favorable entropic contributions and smaller enthalpic contributions. Cell-based assays with HEK293T cells expressing PNMT revealed a cell permeable, intracellular PNMT inhibitor with an IC50 value of 81 nM. Structural analysis demonstrated inhibitor 4 filling catalytic site regions to recapitulate both norepinephrine and SAM interactions. Conformation of the second-generation inhibitor in the catalytic site of PNMT improves contacts relative to those from the first-generation inhibitors. Inhibitor 4 demonstrates up to 51,000-fold specificity for PNMT relative to DNA and protein methyltransferases. Inhibitor 4 also exhibits a 12,000-fold specificity for PNMT over the α2-adrenoceptor.
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Affiliation(s)
- Niusha Mahmoodi
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
| | - Yacoba V T Minnow
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
| | - Rajesh K Harijan
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
| | - Gabriel T Bedard
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
| | - Vern L Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States
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4
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Jędrzejewski M, Szeleszczuk Ł, Pisklak DM. The Reaction Mechanism of Loganic Acid Methyltransferase: A Molecular Dynamics Simulation and Quantum Mechanics Study. Molecules 2023; 28:5767. [PMID: 37570737 PMCID: PMC10420828 DOI: 10.3390/molecules28155767] [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: 07/13/2023] [Revised: 07/26/2023] [Accepted: 07/29/2023] [Indexed: 08/13/2023] Open
Abstract
In this work, the catalytic mechanism of loganic acid methyltransferase was characterized at the molecular level. This enzyme is responsible for the biosynthesis of loganin, which is a precursor for a wide range of biologically active compounds. Due to the lack of detailed knowledge about this process, the aim of this study was the analysis of the structure and activity of loganic acid methyltransferase. Using molecular dynamics (MD) simulations, the native structure of the complex was reconstructed, and the key interactions between the substrate and loganic acid methyltransferase were investigated. Subsequently, the structures obtained from the simulations were used for quantum chemical (QM) calculations. The QM calculations allowed for the exploration of the energetic aspects of the reaction and the characterization of its mechanism. The results obtained in this study suggest the existence of two patterns of interactions between loganic acid methyltransferase and the substrate. The role of residue Q38 in the binding and orientation of the substrate's carboxyl group was also demonstrated. By employing a combined MD and QM approach, the experimental reaction barrier was reproduced, and detailed insights into the enzymatic activity mechanism of loganic acid methyltransferase were revealed.
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Affiliation(s)
| | | | - Dariusz Maciej Pisklak
- Department of Organic and Physical Chemistry, Faculty of Pharmacy, Medical University of Warsaw, Banacha 1, 02-093 Warsaw, Poland; (M.J.); (Ł.S.)
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5
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Neti SS, Wang B, Iwig DF, Onderko EL, Booker SJ. Enzymatic Fluoromethylation Enabled by the S-Adenosylmethionine Analog Te-Adenosyl- L-(fluoromethyl)homotellurocysteine. ACS CENTRAL SCIENCE 2023; 9:905-914. [PMID: 37252363 PMCID: PMC10214534 DOI: 10.1021/acscentsci.2c01385] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Indexed: 05/31/2023]
Abstract
Fluoromethyl, difluoromethyl, and trifluoromethyl groups are present in numerous pharmaceuticals and agrochemicals, where they play critical roles in the efficacy and metabolic stability of these molecules. Strategies for late-stage incorporation of fluorine-containing atoms in molecules have become an important area of organic and medicinal chemistry as well as synthetic biology. Herein, we describe the synthesis and use of Te-adenosyl-L-(fluoromethyl)homotellurocysteine (FMeTeSAM), a novel and biologically relevant fluoromethylating agent. FMeTeSAM is structurally and chemically related to the universal cellular methyl donor S-adenosyl-L-methionine (SAM) and supports the robust transfer of fluoromethyl groups to oxygen, nitrogen, sulfur, and some carbon nucleophiles. FMeTeSAM is also used to fluoromethylate precursors to oxaline and daunorubicin, two complex natural products that exhibit antitumor properties.
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Affiliation(s)
- Syam Sundar Neti
- Department
of Chemistry, Department of Biochemistry and Molecular Biology, and Howard Hughes
Medical Institute, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
| | - Bo Wang
- Department
of Chemistry, Department of Biochemistry and Molecular Biology, and Howard Hughes
Medical Institute, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
| | - David F. Iwig
- Department
of Chemistry, Department of Biochemistry and Molecular Biology, and Howard Hughes
Medical Institute, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
| | - Elizabeth L. Onderko
- Department
of Chemistry, Department of Biochemistry and Molecular Biology, and Howard Hughes
Medical Institute, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
| | - Squire J. Booker
- Department
of Chemistry, Department of Biochemistry and Molecular Biology, and Howard Hughes
Medical Institute, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
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6
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Lu J, Bart AG, Wu Q, Criscione KR, McLeish MJ, Scott EE, Grunewald GL. Structure-Based Drug Design of Bisubstrate Inhibitors of Phenylethanolamine N-Methyltransferase Possessing Low Nanomolar Affinity at Both Substrate Binding Domains 1. J Med Chem 2020; 63:13878-13898. [PMID: 33147410 DOI: 10.1021/acs.jmedchem.0c01475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The enzyme phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) catalyzes the final step in the biosynthesis of epinephrine and is a potential drug target, primarily for the control of hypertension. Unfortunately, many potent PNMT inhibitors also possess significant affinity for the a2-adrenoceptor, which complicates the interpretation of their pharmacology. A bisubstrate analogue approach offers the potential for development of highly selective inhibitors of PNMT. This paper documents the design, synthesis, and evaluation of such analogues, several of which were found to possess human PNMT (hPNMT) inhibitory potency <5 nM versus AdoMet. Site-directed mutagenesis studies were consistent with bisubstrate binding. Two of these compounds (19 and 29) were co-crystallized with hPNMT and the resulting structures revealed both compounds bound as predicted, simultaneously occupying both substrate binding domains. This bisubstrate inhibitor approach has resulted in one of the most potent (20) and selective (vs the a2-adrenoceptor) inhibitors of hPNMT yet reported.
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Affiliation(s)
- Jian Lu
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Aaron G Bart
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Qian Wu
- Department of Chemistry and Chemical Biology, Purdue School of Science, IUPUI, Indianapolis, Indiana 46202, United States
| | - Kevin R Criscione
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Michael J McLeish
- Department of Chemistry and Chemical Biology, Purdue School of Science, IUPUI, Indianapolis, Indiana 46202, United States
| | - Emily E Scott
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Gary L Grunewald
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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7
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Perlinska AP, Kalek M, Christian T, Hou YM, Sulkowska JI. Mg 2+-Dependent Methyl Transfer by a Knotted Protein: A Molecular Dynamics Simulation and Quantum Mechanics Study. ACS Catal 2020; 10:8058-8068. [PMID: 32904895 PMCID: PMC7462349 DOI: 10.1021/acscatal.0c00059] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 06/18/2020] [Indexed: 11/27/2022]
Abstract
![]()
Mg2+ is required for the catalytic activity of TrmD,
a bacteria-specific methyltransferase that is made up of a protein
topological knot-fold, to synthesize methylated m1G37-tRNA
to support life. However, neither the location of Mg2+ in
the structure of TrmD nor its role in the catalytic mechanism is known.
Using molecular dynamics (MD) simulations, we identify a plausible
Mg2+ binding pocket within the active site of the enzyme,
wherein the ion is coordinated by two aspartates and a glutamate.
In this position, Mg2+ additionally interacts with the
carboxylate of a methyl donor cofactor S-adenosylmethionine (SAM).
The computational results are validated by experimental mutation studies,
which demonstrate the importance of the Mg2+-binding residues
for the catalytic activity. The presence of Mg2+ in the
binding pocket induces SAM to adopt a unique bent shape required for
the methyl transfer activity and causes a structural reorganization
of the active site. Quantum mechanical calculations show that the
methyl transfer is energetically feasible only when Mg2+ is bound in the position revealed by the MD simulations, demonstrating
that its function is to align the active site residues within the
topological knot-fold in a geometry optimal for catalysis. The obtained
insights provide the opportunity for developing a strategy of antibacterial
drug discovery based on targeting of Mg2+-binding to TrmD.
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Affiliation(s)
- Agata P. Perlinska
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland
- College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Warsaw 02-097, Poland
| | - Marcin Kalek
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland
| | - Thomas Christian
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, United States
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, United States
| | - Joanna I. Sulkowska
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland
- Faculty of Chemistry, University of Warsaw, Warsaw 02-097, Poland
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8
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Mahmoodi N, Harijan RK, Schramm VL. Transition-State Analogues of Phenylethanolamine N-Methyltransferase. J Am Chem Soc 2020; 142:14222-14233. [PMID: 32702980 DOI: 10.1021/jacs.0c05446] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Phenylethanolamine N-methyltransferase (PNMT) is a critical enzyme in catecholamine synthesis. It transfers the methyl group of S-adenosylmethionine (SAM) to catalyze the synthesis of epinephrine from norepinephrine. Epinephrine has been associated with diverse human processes, including the regulation of blood pressure and respiration, as well as neurodegeneration found in Alzheimer's disease. Human PNMT (hPNMT) proceeds through an SN2 transition state (TS) in which the transfer of the methyl group is rate limiting. TS analogue enzyme inhibitors are specific for their target and bind orders of magnitude more tightly than their substrates. Molecules resembling the TS of hPNMT were designed, synthesized, and kinetically characterized. This new inhibitory scaffold was designed to mimic the geometry and electronic properties of the hPNMT TS. Synthetic efforts resulted in a tight-binding inhibitor with a Ki value of 12.0 nM. This is among the first of the TS analogue inhibitors of methyltransferase enzymes to show an affinity in the nanomolar range. Isothermal titration calorimetry (ITC) measurements indicated negative cooperative binding of inhibitor to the dimeric protein, driven by favorable entropic contributions. Structural analysis revealed that inhibitor 3 binds to hPNMT by filling the catalytic binding pockets for the cofactor (SAM) and the substrate (norepinephrine) binding sites.
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Affiliation(s)
- Niusha Mahmoodi
- Department of Biochemistry, Albert Einstein College of Medicine, New York, New York 10461, United States
| | - Rajesh K Harijan
- Department of Biochemistry, Albert Einstein College of Medicine, New York, New York 10461, United States
| | - Vern L Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, New York, New York 10461, United States
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9
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Dasgupta S, Herbert JM. Using Atomic Confining Potentials for Geometry Optimization and Vibrational Frequency Calculations in Quantum-Chemical Models of Enzyme Active Sites. J Phys Chem B 2020; 124:1137-1147. [PMID: 31986049 DOI: 10.1021/acs.jpcb.9b11060] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Quantum-chemical studies of enzymatic reaction mechanisms sometimes use truncated active-site models as simplified alternatives to mixed quantum mechanics molecular mechanics (QM/MM) procedures. Eliminating the MM degrees of freedom reduces the complexity of the sampling problem, but the trade-off is the need to introduce geometric constraints in order to prevent structural collapse of the model system during geometry optimizations that do not contain a full protein backbone. These constraints may impair the efficiency of the optimization, and care must be taken to avoid artifacts such as imaginary vibrational frequencies. We introduce a simple alternative in which terminal atoms of the model system are placed in soft harmonic confining potentials rather than being rigidly constrained. This modification is simple to implement and straightforward to use in vibrational frequency calculations, unlike iterative constraint-satisfaction algorithms, and allows the optimization to proceed without constraint even though the practical result is to fix the anchor atoms in space. The new approach is more efficient for optimizing minima and transition states, as compared to the use of fixed-atom constraints, and also more robust against unwanted imaginary frequencies. We illustrate the method by application to several enzymatic reaction pathways where entropy makes a significant contribution to the relevant reaction barriers. The use of confining potentials correctly describes reaction paths and facilitates calculation of both vibrational zero-point and finite-temperature entropic corrections to barrier heights.
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Affiliation(s)
- Saswata Dasgupta
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
| | - John M Herbert
- Department of Chemistry and Biochemistry , The Ohio State University , Columbus , Ohio 43210 , United States
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10
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Dalla Torre G, Mujika JI, Lachowicz JI, Ramos MJ, Lopez X. The interaction of aluminum with catecholamine-based neurotransmitters: can the formation of these species be considered a potential risk factor for neurodegenerative diseases? Dalton Trans 2019; 48:6003-6018. [PMID: 30688329 DOI: 10.1039/c8dt04216k] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The potential neurotoxic role of Al(iii) and its proposed link with the insurgence of Alzheimer's Disease (AD) have attracted increasing interest towards the determination of the nature of bioligands that are propitious to interact with aluminum. Among them, catecholamine-based neurotransmitters have been proposed to be sensitive to the presence of this non-essential metal ion in the brain. In the present work, we characterize several aluminum-catecholamine complexes in various stoichiometries, determining their structure and thermodynamics of formation. For this purpose, we apply a recently validated computational protocol with results that show a remarkably good agreement with the available experimental data. In particular, we employ Density Functional Theory (DFT) in conjunction with continuum solvation models to calculate complexation energies of aluminum for a set of four important catecholamines: l-DOPA, dopamine, noradrenaline and adrenaline. In addition, by means of the Quantum Theory of Atoms in Molecules (QTAIM) and Energy Decomposition Analysis (EDA) we assessed the nature of the Al-ligand interactions, finding mainly ionic bonds with an important degree of covalent character. Our results point at the possibility of the formation of aluminum-catecholamine complexes with favorable formation energies, even when proton/aluminum competition is taken into account. Indeed, we found that these catecholamines are better aluminum binders than catechol at physiological pH, because of the electron withdrawing effect of the positively-charged amine that decreases their deprotonation penalty with respect to catechol. However, overall, our results show that, in an open biological environment, the formation of Al-catecholamine complexes is not thermodynamically competitive when compared with the formation of other aluminum species in solution such as Al-hydroxide, or when considering other endogenous/exogenous Al(iii) ligands such as citrate, deferiprone and EDTA. In summary, we rule out the possibility, suggested by some authors, that the formation of Al-catecholamine complexes in solution might be behind some of the toxic roles attributed to aluminum in the brain. An up-to-date view of the catecholamine biosynthesis pathway with sites of aluminum interference (according to the current literature) is presented. Alternative mechanisms that might explain the deleterious effects of this metal on the catecholamine route are thoroughly discussed, and new hypotheses that should be investigated in future are proposed.
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Affiliation(s)
- Gabriele Dalla Torre
- Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi, Spain.
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11
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Stratton CF, Poulin MB, Du Q, Schramm VL. Kinetic Isotope Effects and Transition State Structure for Human Phenylethanolamine N-Methyltransferase. ACS Chem Biol 2017; 12:342-346. [PMID: 27997103 PMCID: PMC5553282 DOI: 10.1021/acschembio.6b00922] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phenylethanolamine N-methyltransferase (PNMT) catalyzes the S-adenosyl-l-methionine (SAM)-dependent conversion of norepinephrine to epinephrine. Epinephrine has been associated with critical processes in humans including the control of respiration and blood pressure. Additionally, PNMT activity has been suggested to play a role in hypertension and Alzheimer's disease. In the current study, labeled SAM substrates were used to measure primary methyl-14C and 36S and secondary methyl-3H, 5'-3H, and 5'-14C intrinsic kinetic isotope effects for human PNMT. The transition state of human PNMT was modeled by matching kinetic isotope effects predicted via quantum chemical calculations to intrinsic values. The model provides information on the geometry and electrostatics of the human PNMT transition state structure and indicates that human PNMT catalyzes the formation of epinephrine through an early SN2 transition state in which methyl transfer is rate-limiting.
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Affiliation(s)
- Christopher F. Stratton
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | | | - Quan Du
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
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12
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Abstract
![]()
Although QM/MM calculations
are the primary current tool for modeling enzymatic reactions, the
reliability of such calculations can be limited by the size of the
QM region. Thus, we examine in this work the dependence of QM/MM calculations
on the size of the QM region, using the reaction of catechol-O-methyl transferase (COMT) as a test case. Our study focuses
on the effect of adding residues to the QM region on the activation
free energy, obtained with extensive QM/MM sampling. It is found that
the sensitivity of the activation barrier to the size of the QM is
rather limited, while the dependence of the reaction free energy is
somewhat larger. Of course, the results depend on the inclusion of
the first solvation shell in the QM regions. For example, the inclusion
of the Mg2+ ion can change the activation barrier due to
charge transfer effects. However, such effects can easily be included
in semiempirical approaches by proper parametrization. Overall, we
establish that QM/MM calculations of activation barriers of enzymatic
reactions are not highly sensitive to the size of the QM region, beyond
the immediate region that describes the reacting atoms.
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13
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Wang L, Zhang T, Li J, He C, He H, Zhang J. Catalytic mechanism of human N-acetylserotonin methyltransferase: a theoretical investigation. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1036143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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14
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Dickschat JS, Rabe P, Citron CA. The chemical biology of dimethylsulfoniopropionate. Org Biomol Chem 2015; 13:1954-68. [DOI: 10.1039/c4ob02407a] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review addresses synthesis, biosynthesis, transport and degradation of dimethylsulfoniopropionate and its derivatives.
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Affiliation(s)
- Jeroen S. Dickschat
- Kekulé-Institut für Organische Chemie und Biochemie
- Rheinische Friedrich-Wilhelms-Universität Bonn
- 53121 Bonn
- Germany
- Institut für Organische Chemie
| | - Patrick Rabe
- Kekulé-Institut für Organische Chemie und Biochemie
- Rheinische Friedrich-Wilhelms-Universität Bonn
- 53121 Bonn
- Germany
- Institut für Organische Chemie
| | - Christian A. Citron
- Kekulé-Institut für Organische Chemie und Biochemie
- Rheinische Friedrich-Wilhelms-Universität Bonn
- 53121 Bonn
- Germany
- Institut für Organische Chemie
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15
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Larabi R, Abtouche S, Brahimi M. Theoretical study of methyl group transfer assisted by proton transfer reaction in the N-acylated imidates. J Mol Model 2014; 20:2302. [DOI: 10.1007/s00894-014-2302-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 05/12/2014] [Indexed: 11/28/2022]
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16
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Wu Q, McLeish MJ. Kinetic and pH studies on human phenylethanolamine N-methyltransferase. Arch Biochem Biophys 2013; 539:1-8. [PMID: 24018397 PMCID: PMC3853373 DOI: 10.1016/j.abb.2013.08.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 08/29/2013] [Accepted: 08/31/2013] [Indexed: 02/04/2023]
Abstract
Phenylethanolamine N-methyltransferase (PNMT) catalyzes the conversion of norepinephrine (noradrenaline) to epinephrine (adrenaline) while, concomitantly, S-adenosyl-L-methionine (AdoMet) is converted to S-adenosyl-L-homocysteine. This reaction represents the terminal step in catecholamine biosynthesis and inhibitors of PNMT have been investigated, inter alia, as potential antihypertensive agents. At various times the kinetic mechanism of PNMT has been reported to operate by a random mechanism, an ordered mechanism in which norepinephrine binds first, and an ordered mechanism in which AdoMet binds first. Here we report the results of initial velocity studies on human PNMT in the absence and presence of product and dead end inhibitors. These, coupled with isothermal titration calorimetry and fluorescence binding experiments, clearly shown that hPNMT operates by an ordered sequential mechanism in which AdoMet binds first. Although the logV pH-profile was not well defined, plots of logV/K versus pH for AdoMet and phenylethanolamine, as well as the pKi versus pH for the inhibitor, SK&F 29661, were all bell-shaped indicating that a protonated and an unprotonated group are required for catalysis.
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Affiliation(s)
- Qian Wu
- Department of Medicinal Chemistry, University of Michigan, 428 Church St, Ann Arbor, Michigan 48105
| | - Michael J. McLeish
- Department of Medicinal Chemistry, University of Michigan, 428 Church St, Ann Arbor, Michigan 48105
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford St. Indianapolis, IN 46202
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Hou Q, Hu X, Sheng X, Liu Y, Liu C. Theoretical study on the degradation of ADP-ribose polymer catalyzed by poly(ADP-ribose) glycohydrolase. J Mol Graph Model 2013; 42:26-31. [PMID: 23524370 DOI: 10.1016/j.jmgm.2013.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 02/25/2013] [Accepted: 02/26/2013] [Indexed: 10/27/2022]
Abstract
Poly(ADP-ribose) glycohydrolase (PARG) is the only enzyme responsible for the degradation of ADP-ribose polymers. Very recently, the first crystal structure of PARG was reported (Dea Slade, et al., Nature 477 (2011) 616), and a possible SN1-type-like mechanism was proposed. In this work, we present a computational study on the hydrolysis of glycosidic ribose-ribose bond catalyzed by PARG using hybrid density functional theory (DFT) methods. Based on the crystal structure of PARG, three models of the active site were constructed. The calculation results suggest that the degradation of poly(ADP-ribose) follows an SN2 mechanism, and the oxocarbenium expected by Dea Slade is a possible transition state but not an intermediate. The calculated reaction pathway agrees with the proposed mechanism. According to the computational models with different sizes, the roles of key residues are elucidated. Our results may provide useful information for the subsequent experimental and theoretical studies on the structure and functional relationships of PARG.
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Affiliation(s)
- Qianqian Hou
- Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
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18
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Hou QQ, Wang JH, Gao J, Liu YJ, Liu CB. QM/MM studies on the catalytic mechanism of phenylethanolamine N-methyltransferase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:533-41. [PMID: 22326747 DOI: 10.1016/j.bbapap.2012.01.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 01/05/2012] [Accepted: 01/26/2012] [Indexed: 02/06/2023]
Abstract
Epinephrine is a naturally occurring adrenomedullary hormone that transduces environmental stressors into cardiovascular actions. As the only route in the catecholamine biosynthetic pathway, Phenylethanolamine N-methyltransferase (PNMT) catalyzes the synthesis of epinephrine. To elucidate the detailed mechanism of enzymatic catalysis of PNMT, combined quantum-mechanical/molecular-mechanical (QM/MM) calculations were performed. The calculation results reveal that this catalysis contains three elementary steps: the deprotonation of protonated norepinphrine, the methyl transferring step and deprotonation of the methylated norepinphrine. The methyl transferring step was proved to be the rate-determining step undergoing a SN2 mechanism with an energy barrier of 16.4kcal/mol. During the whole catalysis, two glutamic acids Glu185 and Glu219 were proved to be loaded with different effects according to the calculations results of the mutants. These calculation results can be used to explain the experimental observations and make a good complementarity for the previous QM study.
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Affiliation(s)
- Q Q Hou
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, China
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19
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Schuller DJ, Reisch CR, Moran MA, Whitman WB, Lanzilotta WN. Structures of dimethylsulfoniopropionate-dependent demethylase from the marine organism Pelagabacter ubique. Protein Sci 2012; 21:289-98. [PMID: 22162093 PMCID: PMC3324773 DOI: 10.1002/pro.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Accepted: 11/29/2011] [Indexed: 02/01/2023]
Abstract
Dimethylsulfoniopropionate (DMSP) is a ubiquitous algal metabolite and common carbon and sulfur source for marine bacteria. DMSP is a precursor for the climatically active gas dimethylsulfide that is readily oxidized to sulfate, sulfur dioxide, methanesulfonic acid, and other products that act as cloud condensation nuclei. Although the environmental importance of DMSP metabolism has been known for some time, the enzyme responsible for DMSP demethylation by marine bacterioplankton, dimethylsufoniopropionate-dependent demethylase A (DmdA, EC 2.1.1.B5), has only recently been identified and biochemically characterized. In this work, we report the structure for the apoenzyme DmdA from Pelagibacter ubique (2.1 Å), as well as for DmdA co-crystals soaked with substrate DMSP (1.6 Å) or the cofactor tetrahydrofolate (THF) (1.6 Å). Surprisingly, the overall fold of the DmdA is not similar to other enzymes that typically utilize the reduced form of THF and in fact is a triple domain structure similar to what has been observed for the glycine cleavage T protein or sarcosine oxidase. Specifically, while the THF binding fold appears conserved, previous biochemical studies have shown that all enzymes with a similar fold produce 5,10-methylene-THF, while DmdA catalyzes a redox-neutral methyl transfer reaction to produce 5-methyl-THF. On the basis of the findings presented herein and the available biochemical data, we outline a mechanism for a redox-neutral methyl transfer reaction that is novel to this conserved THF binding domain.
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Affiliation(s)
- David J Schuller
- Cornell High Energy Synchrotron Source, Cornell UniversityIthaca, New York 14853
| | - Chris R Reisch
- Department of Microbiology, University of GeorgiaAthens, Georgia 30602
| | - Mary Ann Moran
- Department of Marine Sciences, University of GeorgiaAthens, Georgia 30602
| | - William B Whitman
- Department of Microbiology, University of GeorgiaAthens, Georgia 30602
| | - William N Lanzilotta
- Department of Biochemistry and Molecular Biology and The Center for Metalloenzyme Studies, University of GeorgiaAthens, Georgia 30602
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Sousa SF, Fernandes PA, Ramos MJ. Computational enzymatic catalysis – clarifying enzymatic mechanisms with the help of computers. Phys Chem Chem Phys 2012; 14:12431-41. [DOI: 10.1039/c2cp41180f] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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21
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Cui FC, Pan XL, Liu W, Liu JY. Elucidation of the methyl transfer mechanism catalyzed by chalcone O-methyltransferase: A density functional study. J Comput Chem 2011; 32:3068-74. [DOI: 10.1002/jcc.21890] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 05/17/2011] [Accepted: 06/22/2011] [Indexed: 11/07/2022]
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Liao RZ, Georgieva P, Yu JG, Himo F. Mechanism of mycolic acid cyclopropane synthase: a theoretical study. Biochemistry 2011; 50:1505-13. [PMID: 21241051 DOI: 10.1021/bi101493p] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction mechanism of mycolic acid cyclopropane synthase is investigated using hybrid density functional theory. The direct methylation mechanism is examined with a large model of the active site constructed on the basis of the crystal structure of the native enzyme. The important active site residue Glu140 is modeled in both ionized and neutral forms. We demonstrate that the reaction starts via the transfer of a methyl to the substrate double bond, followed by the transfer of a proton from the methyl cation to the bicarbonate present in the active site. The first step is calculated to be rate-limiting, in agreement with experimental kinetic results. The protonation state of Glu140 has a rather weak influence on the reaction energetics. In addition to the natural reaction, a possible side reaction, namely a carbocation rearrangement, is also considered and is shown to have a low barrier. Finally, the energetics for the sulfur ylide proposal, which has already been ruled out, is also estimated, showing a large energetic penalty for ylide formation.
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Affiliation(s)
- Rong-Zhen Liao
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
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