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Nakahara M, Watanabe S, Sato M, Okumura H, Kawatani M, Osada H, Hara K, Hashimoto H, Watanabe K. Structural and Functional Analyses of Inhibition of Human Dihydroorotate Dehydrogenase by Antiviral Furocoumavirin. Biochemistry 2024; 63:1241-1245. [PMID: 38724483 DOI: 10.1021/acs.biochem.4c00120] [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: 05/22/2024]
Abstract
Natural products are important sources of seed compounds for drug discovery. However, it has become difficult in recent years to discover new compounds with valuable pharmacological activities. On the other hand, among the vast number of natural products that have been isolated so far, a considerable number of compounds with specific biological activities are thought to be overlooked in screening that uses biological activity as an index. Therefore, it is conceivable that such overlooked useful compounds may be found by screening compound libraries that have been amassed previously through specific assays. Previously, NPD723, a member of the Natural Products Depository library comprised of a mixture of natural and non-natural products developed at RIKEN, and its metabolite H-006 were found to inhibit growth of various cancer cells at low nanomolar half-maximal inhibitory concentration. Subsequent analysis revealed that H-006 strongly inhibited human dihydroorotate dehydrogenase (DHODH), the rate-limiting enzyme in the de novo pyrimidine biosynthetic pathway. Here, we elucidated the crystal structure of the DHODH-flavin mononucleotide-orotic acid-H-006 complex at 1.7 Å resolution to determine that furocoumavirin, the S-enantiomer of H-006, was the actual inhibitor. The overall mode of interaction of furocoumavirin with the inhibitor binding pocket was similar to that described for previously reported tight-binding inhibitors. However, the structural information together with kinetic characterizations of site-specific mutants identified key unique features that are considered to contribute to the sub-nanomolar inhibition of DHODH by furocoumavirin. Our finding identified new chemical features that could improve the design of human DHODH inhibitors.
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Affiliation(s)
- Miku Nakahara
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
| | - Shogo Watanabe
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
| | - Michio Sato
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
| | | | - Makoto Kawatani
- Chemical Resource Development Research Unit, RIKEN Center for Sustainable Resource Science, Wako-shi 351-0198, Japan
| | - Hiroyuki Osada
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
| | - Kodai Hara
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
| | - Hiroshi Hashimoto
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
| | - Kenji Watanabe
- Department of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
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2
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Garrett O, Whalen KE. A bacterial quorum sensing signal is a potent inhibitor of de novo pyrimidine biosynthesis in the globally abundant Emiliania huxleyi. Front Microbiol 2023; 14:1266972. [PMID: 37869665 PMCID: PMC10587436 DOI: 10.3389/fmicb.2023.1266972] [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: 07/25/2023] [Accepted: 09/08/2023] [Indexed: 10/24/2023] Open
Abstract
Interactions between marine phytoplankton, viruses, and bacteria drive biogeochemical cycling, shape marine trophic structures, and impact global climate. Microbially produced compounds have emerged as key players in influencing eukaryotic organismal physiology, and in turn, remodel microbial community structure. This work aimed to reveal the molecular mechanism by which the bacterial quorum sensing molecule 2-heptyl-4-quinolone (HHQ), produced by the marine gammaproteobacterium Pseudoalteromonas spp., arrests cell division and confers protection from virus-induced mortality in the bloom-forming coccolithophore Emiliania huxleyi. Previous work has established alkylquinolones as inhibitors of dihydroorotate dehydrogenase (DHODH), a fundamental enzyme catalyzing the fourth step in pyrimidine biosynthesis and a potential antiviral drug target. An N-terminally truncated version of E. huxleyi DHODH was heterologously expressed in E. coli, purified, and kinetically characterized. Here, we show HHQ is a potent inhibitor (Ki of 2.3 nM) of E. huxleyi DHODH. E. huxleyi cells exposed to brequinar, the canonical human DHODH inhibitor, experienced immediate, yet reversible cellular arrest, an effect which mirrors HHQ-induced cellular stasis previously observed. However, brequinar treatment lacked other notable effects observed in HHQ-exposed E. huxleyi including significant changes in cell size, chlorophyll fluorescence, and protection from virus-induced lysis, indicating HHQ has additional as yet undiscovered physiological targets. Together, these results suggest a novel and intricate role of bacterial quorum sensing molecules in tripartite interdomain interactions in marine ecosystems, opening new avenues for exploring the role of microbial chemical signaling in algal bloom regulation and host-pathogen dynamics.
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Affiliation(s)
| | - Kristen E. Whalen
- Department of Biology, Haverford College, Haverford, PA, United States
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3
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Horwitz SM, Blue TC, Ambarian JA, Hoshino S, Seyedsayamdost MR, Davis KM. Structural insights into inhibition of the drug target dihydroorotate dehydrogenase by bacterial hydroxyalkylquinolines. RSC Chem Biol 2022; 3:420-425. [PMID: 35441142 PMCID: PMC8984913 DOI: 10.1039/d1cb00255d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Accepted: 02/07/2022] [Indexed: 12/04/2022] Open
Abstract
Hydroxyalkylquinolines (HAQs) are ubiquitious natural products but their interactions with associated protein targets remain elusive. We report X-ray crystal structures of two HAQs in complex with dihydroorotate dehydrogenase (DHODH). Our results reveal the structural basis of DHODH inhibition by HAQs and open the door to downstream structure-activity relationship studies.
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Affiliation(s)
| | - Tamra C Blue
- Department of Chemistry, Emory University Atlanta GA 30322 USA
| | | | - Shotaro Hoshino
- Department of Chemistry, Princeton University Princeton NJ 08544 USA
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4
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Chung I, Serreli R, Cross JB, Di Francesco ME, Marszalek JR, Hirst J. Cork-in-bottle mechanism of inhibitor binding to mammalian complex I. SCIENCE ADVANCES 2021; 7:7/20/eabg4000. [PMID: 33990335 PMCID: PMC8121435 DOI: 10.1126/sciadv.abg4000] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/26/2021] [Indexed: 05/08/2023]
Abstract
Mitochondrial complex I (NADH:ubiquinone oxidoreductase), a major contributor of free energy for oxidative phosphorylation, is increasingly recognized as a promising drug target for ischemia-reperfusion injury, metabolic disorders, and various cancers. Several pharmacologically relevant but structurally unrelated small molecules have been identified as specific complex I inhibitors, but their modes of action remain unclear. Here, we present a 3.0-Å resolution cryo-electron microscopy structure of mammalian complex I inhibited by a derivative of IACS-010759, which is currently in clinical development against cancers reliant on oxidative phosphorylation, revealing its unique cork-in-bottle mechanism of inhibition. We combine structural and kinetic analyses to deconvolute cross-species differences in inhibition and identify the structural motif of a "chain" of aromatic rings as a characteristic that promotes inhibition. Our findings provide insights into the importance of π-stacking residues for inhibitor binding in the long substrate-binding channel in complex I and a guide for future biorational drug design.
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Affiliation(s)
- Injae Chung
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Riccardo Serreli
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Jason B Cross
- Institute for Applied Cancer Science (IACS), The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
| | - M Emilia Di Francesco
- Institute for Applied Cancer Science (IACS), The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
| | - Joseph R Marszalek
- TRACTION-Translational Research to AdvanCe Therapeutics and Innovation in ONcology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
| | - Judy Hirst
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK.
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5
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Nonato MC, de Pádua RA, David JS, Reis RA, Tomaleri GP, D'Muniz Pereira H, Calil FA. Structural basis for the design of selective inhibitors for Schistosoma mansoni dihydroorotate dehydrogenase. Biochimie 2019; 158:180-190. [DOI: 10.1016/j.biochi.2019.01.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 01/10/2019] [Indexed: 10/27/2022]
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Madak JT, Cuthbertson CR, Miyata Y, Tamura S, Petrunak EM, Stuckey JA, Han Y, He M, Sun D, Showalter HD, Neamati N. Design, Synthesis, and Biological Evaluation of 4-Quinoline Carboxylic Acids as Inhibitors of Dihydroorotate Dehydrogenase. J Med Chem 2018; 61:5162-5186. [PMID: 29727569 DOI: 10.1021/acs.jmedchem.7b01862] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We pursued a structure-guided approach toward the development of improved dihydroorotate dehydrogenase (DHODH) inhibitors with the goal of forming new interactions between DHODH and the brequinar class of inhibitors. Two potential residues, T63 and Y356, suitable for novel H-bonding interactions, were identified in the brequinar-binding pocket. Analogues were designed to maintain the essential pharmacophore and form new electrostatic interactions through strategically positioned H-bond accepting groups. This effort led to the discovery of potent quinoline-based analogues 41 (DHODH IC50 = 9.71 ± 1.4 nM) and 43 (DHODH IC50 = 26.2 ± 1.8 nM). A cocrystal structure between 43 and DHODH depicts a novel water mediated H-bond interaction with T63. Additional optimization led to the 1,7-naphthyridine 46 (DHODH IC50 = 28.3 ± 3.3 nM) that forms a novel H-bond with Y356. Importantly, compound 41 possesses significant oral bioavailability ( F = 56%) and an elimination t1/2 = 2.78 h (PO dosing). In conclusion, the data supports further preclinical studies of our lead compounds toward selection of a candidate for early-stage clinical development.
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Affiliation(s)
| | | | | | | | - Elyse M Petrunak
- Life Sciences Institute and Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Jeanne A Stuckey
- Life Sciences Institute and Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
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7
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In Silico study of the active site of Helicobacter pylori urease and its inhibition by hydroxamic acids. J Mol Graph Model 2018; 83:64-73. [PMID: 29775804 DOI: 10.1016/j.jmgm.2018.04.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 04/26/2018] [Accepted: 04/27/2018] [Indexed: 11/21/2022]
Abstract
Hydroxamic acids have emerged as the most promising candidates from among the different classes of inhibitors of urease. In order to understand the mechanism of their action, we have studied in detail using quantum mechanics the active site of Helicobacter pylori urease complexed with acetohydroxamic acid. A diverse library of ligands having the hydroxamate moiety has been prepared and docked into the active site of urease using the QM/MM methodology. It is found that hydroxamic acids with hydrophobic groups attached to them are more potent inhibitors of urease because they can easily penetrate the hydrophobic environment surrounding the active site. The -CONHO- moiety of the hydroxamic acid is also found to be absolutely necessary for chelation and inhibition of urease. In order to determine the roles of residues His 221 and Ala 365, which are not part of the active site, but are nevertheless involved in hydrogen bonding with the ligand, we have performed Molecular Dynamics simulations, both on the wild urease and also on its mutated counterpart, with the two residues substituted, respectively, by alanine and glycine.
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8
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Saturation mutagenesis of putative catalytic residues of benzoylformate decarboxylase provides a challenge to the accepted mechanism. Proc Natl Acad Sci U S A 2008; 105:5733-8. [PMID: 18398009 DOI: 10.1073/pnas.0709657105] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Benzoylformate decarboxylase from Pseudomonas putida (PpBFDC) is a thiamin diphosphate-dependent enzyme that carries out the nonoxidative decarboxylation of aromatic 2-keto acids. The x-ray structure of PpBFDC suggested that Ser-26, His-70, and His-281 would play important roles in its catalytic mechanism, and the S26A, H70A, and H281A variants all exhibited greatly impaired catalytic activity. Based on stopped-flow studies with the alanine mutants, it was proposed that the histidine residues acted as acid-base catalysts, whereas Ser-26 was involved in substrate binding and played a significant, albeit less well defined, role in catalysis. While developing a saturation mutagenesis protocol to examine residues involved in PpBFDC substrate specificity, we tested the procedure on His-281. To our surprise, we found that His-281, which is thought to be necessary for protonation of the carbanion/enamine intermediate, could be replaced by phenyl alanine with only a 5-fold decrease in k(cat). Even more surprising were our subsequent observations (i) that His-70 could be replaced by threonine or leucine with approximately a 30-fold decrease in k(cat)/K(m) compared with a 4,000-fold decrease for the H70A variant and (ii) that Ser-26, which forms hydrogen bonds with the substrate carboxylate, could be replaced by threonine, leucine, or methionine without significant loss of activity. These results call into question the assigned roles for Ser-26, His-70, and His-281. Further, they demonstrate the danger in assigning catalytic function based solely on results with alanine mutants and show that saturation mutagenesis is a valuable tool in assessing the role and relative importance of putative catalytic residues.
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9
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Baldwin J, Michnoff CH, Malmquist NA, White J, Roth MG, Rathod PK, Phillips MA. High-throughput screening for potent and selective inhibitors of Plasmodium falciparum dihydroorotate dehydrogenase. J Biol Chem 2005; 280:21847-53. [PMID: 15795226 DOI: 10.1074/jbc.m501100200] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plasmodium falciparum is the causative agent of the most serious and fatal malarial infections, and it has developed resistance to commonly employed chemotherapeutics. The de novo pyrimidine biosynthesis enzymes offer potential as targets for drug design, because, unlike the host, the parasite does not have pyrimidine salvage pathways. Dihydroorotate dehydrogenase (DHODH) is a flavin-dependent mitochondrial enzyme that catalyzes the fourth reaction in this essential pathway. Coenzyme Q (CoQ) is utilized as the oxidant. Potent and species-selective inhibitors of malarial DHODH were identified by high-throughput screening of a chemical library, which contained 220,000 drug-like molecules. These novel inhibitors represent a diverse range of chemical scaffolds, including a series of halogenated phenyl benzamide/naphthamides and urea-based compounds containing napthyl or quinolinyl substituents. Inhibitors in these classes with IC(50) values below 600 nm were purified by high pressure liquid chromatography, characterized by mass spectroscopy, and subjected to kinetic analysis against the parasite and human enzymes. The most active compound is a competitive inhibitor of CoQ with an IC(50) against malarial DHODH of 16 nm, and it is 12,500-fold less active against the human enzyme. Site-directed mutagenesis of residues in the CoQ-binding site significantly reduced inhibitor potency. The structural basis for the species selective enzyme inhibition is explained by the variable amino acid sequence in this binding site, making DHODH a particularly strong candidate for the development of new anti-malarial compounds.
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Affiliation(s)
- Jeffrey Baldwin
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA
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10
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Hansen M, Le Nours J, Johansson E, Antal T, Ullrich A, Löffler M, Larsen S. Inhibitor binding in a class 2 dihydroorotate dehydrogenase causes variations in the membrane-associated N-terminal domain. Protein Sci 2004; 13:1031-42. [PMID: 15044733 PMCID: PMC2280058 DOI: 10.1110/ps.03533004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The flavin enzyme dihydroorotate dehydrogenase (DHOD; EC 1.3.99.11) catalyzes the oxidation of dihydroorotate to orotate, the fourth step in the de novo pyrimidine biosynthesis of UMP. The enzyme is a promising target for drug design in different biological and clinical applications for cancer and arthritis. The first crystal structure of the class 2 dihydroorotate dehydrogenase from rat has been determined in complex with its two inhibitors brequinar and atovaquone. These inhibitors have shown promising results as anti-proliferative, immunosuppressive, and antiparasitic agents. A unique feature of the class 2 DHODs is their N-terminal extension, which folds into a separate domain comprising two alpha-helices. This domain serves as the binding site for the two inhibitors and the respiratory quinones acting as the second substrate for the class 2 DHODs. The orientation of the first N-terminal helix is very different in the two complexes of rat DHOD (DHODR). Binding of atovaquone causes a 12 A movement of the first residue in the first alpha-helix. Based on the information from the two structures of DHODR, a model for binding of the quinone and the residues important for the interactions could be defined. His 56 and Arg 136, which are fully conserved in all class 2 DHODs, seem to play a key role in the interaction with the electron acceptor. The differences between the membrane-bound rat DHOD and membrane-associated class 2 DHODs exemplified by the Escherichia coli DHOD has been investigated by GRID computations of the hydrophobic probes predicted to interact with the membrane.
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Affiliation(s)
- Majbritt Hansen
- Centre for Crystallographic Studies, Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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Ullrich A, Knecht W, Fries M, Löffler M. Recombinant expression of N-terminal truncated mutants of the membrane bound mouse, rat and human flavoenzyme dihydroorotate dehydrogenase. ACTA ACUST UNITED AC 2003. [DOI: 10.1046/j.1432-1327.2001.02061.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Nørager S, Arent S, Björnberg O, Ottosen M, Lo Leggio L, Jensen KF, Larsen S. Lactococcus lactis dihydroorotate dehydrogenase A mutants reveal important facets of the enzymatic function. J Biol Chem 2003; 278:28812-22. [PMID: 12732650 DOI: 10.1074/jbc.m303767200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dihydroorotate dehydrogenases (DHODs) are flavoenzymes catalyzing the oxidation of (S)-dihydroorotate to orotate in the biosynthesis of UMP, the precursor of all other pyrimidine nucleotides. On the basis of sequence, DHODs can be divided into two classes, class 1, further divided in subclasses 1A and 1B, and class 2. This division corresponds to differences in cellular location and the nature of the electron acceptor. Herein we report a study of Lactococcus lactis DHODA, a representative of the class 1A enzymes. Based on the DHODA structure we selected seven residues that are highly conserved between both main classes of DHODs as well as three residues representing surface charges close to the active site for site-directed mutagenesis. The availability of both kinetic and structural data on the mutant enzymes allowed us to define the roles individual structural segments play in catalysis. We have also structurally proven the presence of an open active site loop in DHODA and obtained information about the interactions that control movements of loops around the active site. Furthermore, in one mutant structure we observed differences between the two monomers of the dimer, confirming an apparent asymmetry between the two substrate binding sites that was indicated by the kinetic results.
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Affiliation(s)
- Sofie Nørager
- Centre for Crystallographic Studies, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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Haque TS, Tadesse S, Marcinkeviciene J, Rogers MJ, Sizemore C, Kopcho LM, Amsler K, Ecret LD, Zhan DL, Hobbs F, Slee A, Trainor GL, Stern AM, Copeland RA, Combs AP. Parallel synthesis of potent, pyrazole-based inhibitors of Helicobacter pylori dihydroorotate dehydrogenase. J Med Chem 2002; 45:4669-78. [PMID: 12361393 DOI: 10.1021/jm020112w] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The identification of several potent pyrazole-based inhibitors of bacterial dihydroorotate dehydrogenase (DHODase) via a directed parallel synthetic approach is described below. The initial pyrazole-containing lead compounds were optimized for potency against Helicobacter pylori DHODase. Using three successive focused libraries, inhibitors were rapidly identified with the following characteristics: K(i) < 10 nM against H. pylori DHODase, sub-microg/mL H. pylori minimum inhibitory concentration activity, low molecular weight, and >10 000-fold selectivity over human DHODase.
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Affiliation(s)
- Tasir S Haque
- Department of Medicinal Chemistry, Bristol-Myers Squibb Company, Experimental Station, Route 141 and Henry Clay Road, Wilmington, Delaware 19880, USA.
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14
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Ullrich A, Knecht W, Piskur J, Löffler M. Plant dihydroorotate dehydrogenase differs significantly in substrate specificity and inhibition from the animal enzymes. FEBS Lett 2002; 529:346-50. [PMID: 12372626 DOI: 10.1016/s0014-5793(02)03425-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The mitochondrial membrane bound dihydroorotate dehydrogenase (DHODH; EC 1.3.99.11) catalyzes the fourth step of pyrimidine biosynthesis. By the present correction of a known cDNA sequence for Arabidopsis thaliana DHODH we revealed the importance of the very C-terminal part for its catalytic activity and the reason why--in contrast to mammalian and insect species--the recombinant plant flavoenzyme was unaccessible to date for in vitro characterization. Structure-activity relationship studies explained that potent inhibitors of animal DHODH do not significantly affect the plant enzyme. These difference could be exploited for a novel approach to herb or pest growth control by limitation of pyrimidine nucleotide pools.
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Affiliation(s)
- Alexandra Ullrich
- Institute for Physiological Chemistry, Philipps-University, Karl-von-Frisch-Strasse 1, D-35033 Marburg, Germany.
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Nørager S, Jensen KF, Björnberg O, Larsen S. E. coli dihydroorotate dehydrogenase reveals structural and functional distinctions between different classes of dihydroorotate dehydrogenases. Structure 2002; 10:1211-23. [PMID: 12220493 DOI: 10.1016/s0969-2126(02)00831-6] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The flavoenzymes dihydroorotate dehydrogenases (DHODs) catalyze the fourth and only redox step in the de novo biosynthesis of UMP. Enzymes belonging to class 2, according to their amino acid sequence, are characterized by having a serine residue as the catalytic base and a longer N terminus. The structure of class 2 E. coli DHOD, determined by MAD phasing, showed that the N-terminal extension forms a separate domain. The catalytic serine residue has an environment differing from the equivalent cysteine in class 1 DHODs. Significant differences between the two classes of DHODs were identified by comparison of the E. coli DHOD with the other known DHOD structures, and differences with the class 2 human DHOD explain the variation in their inhibitors.
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Affiliation(s)
- Sofie Nørager
- Centre for Crystallographic Studies, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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16
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Liu S, Neidhardt EA, Grossman TH, Ocain T, Clardy J. Structures of human dihydroorotate dehydrogenase in complex with antiproliferative agents. Structure 2000; 8:25-33. [PMID: 10673429 DOI: 10.1016/s0969-2126(00)00077-0] [Citation(s) in RCA: 225] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Dihydroorotate dehydrogenase (DHODH) catalyzes the fourth committed step in the de novo biosynthesis of pyrimidines. As rapidly proliferating human T cells have an exceptional requirement for de novo pyrimidine biosynthesis, small molecule DHODH inhibitors constitute an attractive therapeutic approach to autoimmune diseases, immunosuppression, and cancer. Neither the structure of human DHODH nor any member of its family was known. RESULTS The high-resolution crystal structures of human DHODH in complex with two different inhibitors have been solved. The initial set of phases was obtained using multiwavelength anomalous diffraction phasing with selenomethionine-containing DHODH. The structures have been refined to crystallographic R factors of 16.8% and 16.2% at resolutions of 1. 6 A and 1.8 A for inhibitors related to brequinar and leflunomide, respectively. CONCLUSIONS Human DHODH has two domains: an alpha/beta-barrel domain containing the active site and an alpha-helical domain that forms the opening of a tunnel leading to the active site. Both inhibitors share a common binding site in this tunnel, and differences in the binding region govern drug sensitivity or resistance. The active site of human DHODH is generally similar to that of the previously reported bacterial active site. The greatest differences are that the catalytic base removing the proton from dihydroorotate is a serine rather than a cysteine, and that packing of the flavin mononucleotide in its binding site is tighter.
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Affiliation(s)
- S Liu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301, USA
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Cummins PM, Pabon A, Margulies EH, Glucksman MJ. Zinc coordination and substrate catalysis within the neuropeptide processing enzyme endopeptidase EC 3.4.24.15. Identification of active site histidine and glutamate residues. J Biol Chem 1999; 274:16003-9. [PMID: 10347149 DOI: 10.1074/jbc.274.23.16003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endopeptidase EC 3.4.24.15 (EP24.15) is a zinc metalloendopeptidase that is broadly distributed within the brain, pituitary, and gonads. Its substrate specificity includes a number of physiologically important neuropeptides such as neurotensin, bradykinin, and gonadotropin-releasing hormone, the principal regulatory peptide for reproduction. In studying the structure and function of EP24.15, we have employed in vitro mutagenesis and subsequent protein expression to genetically dissect the enzyme and allow us to glean insight into the mechanism of substrate binding and catalysis. Comparison of the sequence of EP24.15 with bacterial homologues previously solved by x-ray crystallography and used as models for mammalian metalloendopeptidases, indicates conserved residues. The active site of EP24.15 exhibits an HEXXH motif, a common feature of zinc metalloenzymes. Mutations have confirmed the importance, for binding and catalysis, of the residues (His473, Glu474, and His477) within this motif. A third putative metal ligand, presumed to coordinate directly to the active site zinc ion in concert with His473 and His477, has been identified as Glu502. Conservative alterations to these residues drastically reduces enzymatic activity against both a putative physiological substrate and a synthetic quenched fluorescent substrate as well as binding of the specific active site-directed inhibitor, N-[1-(RS)-carboxy-3-phenylpropyl]-Ala-Ala-Tyr-p-aminobenzoate, the binding of which we have shown to be dependent upon the presence, and possibly coordination, of the active site zinc ion. These studies contribute to a more complete understanding of the catalytic mechanism of EP24.15 and will aid in rational design of inhibitors and pharmacological agents for this class of enzymes.
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Affiliation(s)
- P M Cummins
- Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029-6574, USA
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