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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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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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Nair PC, Malde AK, Mark AE. Using Theory to Reconcile Experiment: The Structural and Thermodynamic Basis of Ligand Recognition by Phenylethanolamine N-Methyltransferase (PNMT). J Chem Theory Comput 2011; 7:1458-68. [DOI: 10.1021/ct1007229] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Pramod C. Nair
- School of Chemistry and Molecular Biosciences (SCMB) and ‡Institute for Molecular Bioscience (IMB), The University of Queensland (UQ), St. Lucia Campus, Brisbane, QLD 4072 Australia
| | - Alpeshkumar K. Malde
- School of Chemistry and Molecular Biosciences (SCMB) and ‡Institute for Molecular Bioscience (IMB), The University of Queensland (UQ), St. Lucia Campus, Brisbane, QLD 4072 Australia
| | - Alan E. Mark
- School of Chemistry and Molecular Biosciences (SCMB) and ‡Institute for Molecular Bioscience (IMB), The University of Queensland (UQ), St. Lucia Campus, Brisbane, QLD 4072 Australia
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Jeong KW, Kang DI, Lee JY, Kim YM. Mutagenic Analysis of hPNMT Confirms the Importance of Lys57 and the Inhibitor Binding Site. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.2.455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Kang DI, Lee JY, Kim W, Jeong KW, Shin S, Yang J, Park E, Chae YK, Kim Y. Discovery of novel human phenylethanolamine N-methyltransferase (hPNMT) inhibitors using 3D pharmacophore-based in silico, biophysical screening and enzymatic activity assays. Mol Cells 2010; 29:595-602. [PMID: 20496117 DOI: 10.1007/s10059-010-0074-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 03/09/2010] [Indexed: 10/19/2022] Open
Abstract
With the aid of receptor-oriented pharmacophore-based in silico screening, we established three pharmacophore maps explaining the binding model of hPNMT and a known inhibitor, SK&F 29661 (Martin et al., 2001). The compound library was searched using these maps. Nineteen selected candidate inhibitors of hPNMT were screened using STD-NMR and fluorescence experiments. An enzymatic activity assay based on HPLC was additionally performed. Consequently, three potential hPNMT inhibitors were identified, specifically, 4-oxo-1,4-dihydroquinoline-3,7-dicarboxylic acid, 4-(benzo[d][1,3]dioxol-5-ylamino)-4-oxobutanoic acid, and 1,4-diaminonaphthalene-2,6-disulfonic acid. These novel inhibitors were retrieved using Map II comprising one hydrogen bond acceptor, one hydrogen bond donor, one lipophilic feature, and shape constraints, including a hydrogen bond between Lys57 of hPNMT and a hydrogen bond donor of the inhibitor, and stacked hydrophobic interactions between the side-chain of Phe182 and an aromatic region of the inhibitor. Water-mediated interactions between Asn267 and Asn39 of hPNMT and the amide or amine group of three potent inhibitors were additional important features for hPNMT activity. The binding model presented here may be applied to identify inhibitors with higher potency. Moreover, our novel compounds are valuable candidates for further lead optimization of PNMT inhibitors.
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Affiliation(s)
- Dong-Il Kang
- Department of Chemistry, Konkuk University, Seoul, 143-701, Korea
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Georgieva P, Wu Q, McLeish MJ, Himo F. The reaction mechanism of phenylethanolamine N-methyltransferase: a density functional theory study. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:1831-7. [PMID: 19733262 DOI: 10.1016/j.bbapap.2009.08.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 08/05/2009] [Accepted: 08/26/2009] [Indexed: 02/06/2023]
Abstract
Hybrid density functional theory methods were used to investigate the reaction mechanism of human phenylethanolamine N-methyltransferase (hPNMT). This enzyme catalyzes the S-adenosyl-L-methionine-dependent conversion of norepinephrine to epinephrine, which constitutes the terminal step in the catecholamine biosynthesis. Several models of the active site were constructed based on the X-ray structure. Geometries of the stationary points along the reaction path were optimized and the reaction barrier and energy were calculated and compared to the experimental values. The calculations demonstrate that the reaction takes place via an SN2 mechanism with methyl transfer being rate-limiting, a suggestion supported by mutagenesis studies. Optimal agreement with experimental data is reached using a model in which both active site glutamates are protonated. Overall, the mechanism of hPNMT is more similar to those of catechol O-methyltransferase and glycine N-methyltransferase than to that of guanidinoacetate N-methyltransferase in which methyl transfer is coupled to proton transfer.
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Affiliation(s)
- Polina Georgieva
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-106 91 Stockholm, Sweden
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Molecular recognition of physiological substrate noradrenaline by the adrenaline-synthesizing enzyme PNMT and factors influencing its methyltransferase activity. Biochem J 2009; 422:463-71. [PMID: 19570037 DOI: 10.1042/bj20090702] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Substrate specificity is critically important for enzyme catalysis. In the adrenaline-synthesizing enzyme PNMT (phenylethanolamine N-methyltransferase), minor changes in substituents can convert substrates into inhibitors. Here we report the crystal structures of six human PNMT complexes, including the first structure of the enzyme in complex with its physiological ligand R-noradrenaline. Determining this structure required rapid soak methods because of the tendency for noradrenaline to oxidize. Comparison of the PNMT-noradrenaline complex with the previously determined PNMT-p-octopamine complex demonstrates that these two substrates form almost equivalent interactions with the enzyme and show that p-octopamine is a valid model substrate for PNMT. The crystal structures illustrate the adaptability of the PNMT substrate binding site in accepting multi-fused ring systems, such as substituted norbornene, as well as noradrenochrome, the oxidation product of noradrenaline. These results explain why only a subset of ligands recognized by PNMT are methylated by the enzyme; bulky substituents dictate the binding orientation of the ligand and can thereby place the acceptor amine too far from the donor methyl group for methylation to occur. We also show how the critical Glu(185) catalytic residue can be replaced by aspartic acid with a loss of only 10-fold in catalytic efficiency. This is because protein backbone movements place the Asp(185) carboxylate almost coincident with the carboxylate of Glu(185). Conversely, replacement of Glu(185) by glutamine reduces catalytic efficiency almost 300-fold, not only because of the loss of charge, but also because the variant residue does not adopt the same conformation as Glu(185).
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Kirk KL. Fluorination in Medicinal Chemistry: Methods, Strategies, and Recent Developments. Org Process Res Dev 2008. [DOI: 10.1021/op700134j] [Citation(s) in RCA: 953] [Impact Index Per Article: 59.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Kenneth L. Kirk
- Laboratory of Bioorganic Chemistry, National Institute Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, U.S.A
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Grunewald GL, Seim MR, Bhat SR, Wilson ME, Criscione KR. Synthesis of 4,5,6,7-tetrahydrothieno[3,2-c]pyridines and comparison with their isosteric 1,2,3,4-tetrahydroisoquinolines as inhibitors of phenylethanolamine N-methyltransferase. Bioorg Med Chem 2008; 16:542-59. [PMID: 18024134 PMCID: PMC2269732 DOI: 10.1016/j.bmc.2007.08.066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Revised: 08/23/2007] [Accepted: 08/28/2007] [Indexed: 11/30/2022]
Abstract
A series of substituted 4,5,6,7-tetrahydrothieno[3,2-c]pyridines (THTPs) was synthesized and evaluated for their human phenylethanolamine N-methyltransferase (hPNMT) inhibitory potency and affinity for the alpha(2)-adrenoceptor. The THTP nucleus was suggested as an isosteric replacement for the 1,2,3,4-tetrahydroisoquinoline (THIQ) ring system on the basis that 3-thienylmethylamine (18) was more potent as an inhibitor of hPNMT and more selective toward the alpha(2)-adrenoceptor than benzylamine (15). Although the isosterism was confirmed, with similar influence of functional groups and chirality in both systems on hPNMT inhibitory potency and selectivity, the THTP compounds proved, in general, to be less potent as inhibitors of hPNMT than their THIQ counterparts, with the drop in potency being primarily attributed to the electronic properties of the thiophene ring. A hypothesis for the reduced hPNMT inhibitory potency of these compounds has been formed on the basis of molecular modeling and docking studies using the X-ray crystal structures of hPNMT co-crystallized with THIQ-type inhibitors and S-adenosyl-L-homocysteine as a template.
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Affiliation(s)
- Gary L Grunewald
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
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Grunewald GL, Seim MR, Lu J, Makboul M, Criscione KR. Application of the Goldilocks effect to the design of potent and selective inhibitors of phenylethanolamine N-methyltransferase: balancing pKa and steric effects in the optimization of 3-methyl-1,2,3,4-tetrahydroisoquinoline inhibitors by beta-fluorination. J Med Chem 2006; 49:2939-52. [PMID: 16686536 PMCID: PMC2770873 DOI: 10.1021/jm051262k] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
3-Methyl-1,2,3,4-tetrahydroisoquinolines (3-methyl-THIQs) are potent inhibitors of phenylethanolamine N-methyltransferase (PNMT), but are not selective due to significant affinity for the alpha(2)-adrenoceptor. Fluorination of the methyl group lowers the pK(a) of the THIQ amine from 9.53 (CH(3)) to 7.88 (CH(2)F), 6.42 (CHF(2)), and 4.88 (CF(3)). This decrease in pK(a) results in a reduction in affinity for the alpha(2)-adrenoceptor. However, increased fluorination also results in a reduction in PNMT inhibitory potency, apparently due to steric and electrostatic factors. Biochemical evaluation of a series of 3-fluoromethyl-THIQs and 3-trifluoromethyl-THIQs showed that the former were highly potent inhibitors of PNMT, but were often nonselective due to significant affinity for the alpha(2)-adrenoceptor, while the latter were devoid of alpha(2)-adrenoceptor affinity, but also lost potency at PNMT. 3-Difluoromethyl-7-substituted-THIQs have the proper balance of both steric and pK(a) properties and thus have enhanced selectivity versus the corresponding 3-fluoromethyl-7-substituted-THIQs and enhanced PNMT inhibitory potency versus the corresponding 3-trifluoromethyl-7-substituted-THIQs. Using the "Goldilocks Effect" analogy, the 3-fluoromethyl-THIQs are too potent (too hot) at the alpha(2)-adrenoceptor and the 3-trifluoromethyl-THIQs are not potent enough (too cold) at PNMT, but the 3-difluoromethyl-THIQs are just right. They are both potent inhibitors of PNMT and highly selective due to low affinity for the alpha(2)-adrenoceptor. This seems to be the first successful use of the beta-fluorination of aliphatic amines to impart selectivity to a pharmacological agent while maintaining potency at the site of interest.
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Affiliation(s)
- Gary L Grunewald
- Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045, USA.
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Grunewald GL, Lu J, Criscione KR, Okoro CO. Inhibitors of phenylethanolamine N-methyltransferase devoid of α2-adrenoceptor affinity. Bioorg Med Chem Lett 2005; 15:5319-23. [PMID: 16169723 DOI: 10.1016/j.bmcl.2005.08.033] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Revised: 08/05/2005] [Accepted: 08/09/2005] [Indexed: 11/19/2022]
Abstract
A series of 3-trifluoromethyl-1,2,3,4-tetrahydroisoquinolines was synthesized and evaluated for their phenylethanolamine N-methyltransferase (PNMT) inhibitory potency and affinity for the alpha(2)-adrenoceptor. Although their PNMT inhibitory potency decreased compared with corresponding 3-methyl-, 3-hydroxymethyl- or 3-unsubstituted-THIQs, some of them showed good selectivity due to their extremely low alpha(2)-adrenoceptor affinity.
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Affiliation(s)
- Gary L Grunewald
- Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
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Sun A, Lankin DC, Hardcastle K, Snyder JP. 3-Fluoropiperidines andN-Methyl-3-fluoropiperidinium Salts: The Persistence of Axial Fluorine. Chemistry 2005; 11:1579-91. [PMID: 15662680 DOI: 10.1002/chem.200400835] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
It has previously been shown that the fluorine atom in N-protonated 3-fluoropiperidine salts in water strongly prefers the axial orientation in the six-membered ring chairs. In the present work we examine the proposition that the N-methyl salts are equally disposed to present axial fluorine. Initially, we explored this point by comparing the structures of the corresponding NH2+, NHMe+, and NMe2+ salts by means of density functional theory (DFT), ab initio, and MMFF force field calculations with and without aqueous solvation models. The predictions unambiguously pointed to axial fluorine for all salts investigated, including those with simultaneous axial F and (N)Me. The calculations were followed by synthesis of the corresponding series of 4,4-diphenylpiperidinium salts. These were evaluated by one- and two-dimensional NMR spectroscopy in [D6]DMSO to fully corroborate the axial disposition of the fluorine in each of the compounds. X-ray crystal structure determinations were likewise performed for the diphenyl-3-fluoro NH2+ and NMe2+ systems to substantiate axial-F. Comparison of the X-ray structures of the fluorinated and unfluorinated NMe2+ salts reveals that the fluorine resides axial in spite of substantial steric compression. While the charge-dipole phenomenon responsible for the axial-F conformation in the parent protonated fluoropiperidinium compounds carries over to doubly alkylated salts, we show that it extends to molecular orientation in the packing of the unit cells in the solid state as well. Finally, using the computational methods that successfully motivated our synthesis and structural work, we have made predictions for a number of new structures and re-examined some parallel results reported by the Eliel group in the early 1970s. Although C-F...H-N hydrogen bonds are reported to be weak and few in number, the CF...HN charge-dipole orienting effect is a powerful directing force that matches the hydrogen-bond in both its energetic contribution and conformational consequences.
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Affiliation(s)
- Aiming Sun
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
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