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Alqahtani SS, Koltai T, Ibrahim ME, Bashir AHH, Alhoufie STS, Ahmed SBM, Molfetta DD, Carvalho TMA, Cardone RA, Reshkin SJ, Hifny A, Ahmed ME, Alfarouk KO. Role of pH in Regulating Cancer Pyrimidine Synthesis. J Xenobiot 2022; 12:158-180. [PMID: 35893264 PMCID: PMC9326563 DOI: 10.3390/jox12030014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 06/17/2022] [Accepted: 06/28/2022] [Indexed: 11/18/2022] Open
Abstract
Replication is a fundamental aspect of cancer, and replication is about reproducing all the elements and structures that form a cell. Among them are DNA, RNA, enzymes, and coenzymes. All the DNA is doubled during each S (synthesis) cell cycle phase. This means that six billion nucleic acids must be synthesized in each cycle. Tumor growth, proliferation, and mutations all depend on this synthesis. Cancer cells require a constant supply of nucleotides and other macromolecules. For this reason, they must stimulate de novo nucleotide synthesis to support nucleic acid provision. When deregulated, de novo nucleic acid synthesis is controlled by oncogenes and tumor suppressor genes that enable increased synthesis and cell proliferation. Furthermore, cell duplication must be achieved swiftly (in a few hours) and in the midst of a nutrient-depleted and hypoxic environment. This also means that the enzymes participating in nucleic acid synthesis must work efficiently. pH is a critical factor in enzymatic efficiency and speed. This review will show that the enzymatic machinery working in nucleic acid synthesis requires a pH on the alkaline side in most cases. This coincides with many other pro-tumoral factors, such as the glycolytic phenotype, benefiting from an increased intracellular pH. An increased intracellular pH is a perfect milieu for high de novo nucleic acid production through optimal enzymatic performance.
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Affiliation(s)
- Saad Saeed Alqahtani
- Department of Pharmacy Practice, College of Pharmacy, Jazan University, Jazan 45142, Saudi Arabia;
- Pharmacy Practice Research Unit, College of Pharmacy, Jazan University, Jazan 45142, Saudi Arabia
| | | | - Muntaser E. Ibrahim
- Department of Molecular Biology, Institute of Endemic Diseases, University of Khartoum, Khartoum 11111, Sudan; (M.E.I.); (A.H.H.B.)
| | - Adil H. H. Bashir
- Department of Molecular Biology, Institute of Endemic Diseases, University of Khartoum, Khartoum 11111, Sudan; (M.E.I.); (A.H.H.B.)
| | - Sari T. S. Alhoufie
- Medical Laboratories Technology Department, College of Applied Medical Sciences, Taibah University, Medina 42353, Saudi Arabia;
| | - Samrein B. M. Ahmed
- Department of Biosciences and Chemistry, College of Health, Wellbeing and Life Sciences, Sheffield Hallam University, Sheffield S1 1WB, UK;
| | - Daria Di Molfetta
- Department of Biosciences, Biotechnologies, and Biopharmaceutics, University of Bari, 70126 Bari, Italy; (D.D.M.); (T.M.A.C.); (R.A.C.); (S.J.R.)
| | - Tiago M. A. Carvalho
- Department of Biosciences, Biotechnologies, and Biopharmaceutics, University of Bari, 70126 Bari, Italy; (D.D.M.); (T.M.A.C.); (R.A.C.); (S.J.R.)
| | - Rosa Angela Cardone
- Department of Biosciences, Biotechnologies, and Biopharmaceutics, University of Bari, 70126 Bari, Italy; (D.D.M.); (T.M.A.C.); (R.A.C.); (S.J.R.)
| | - Stephan Joel Reshkin
- Department of Biosciences, Biotechnologies, and Biopharmaceutics, University of Bari, 70126 Bari, Italy; (D.D.M.); (T.M.A.C.); (R.A.C.); (S.J.R.)
| | | | - Mohamed E. Ahmed
- Research Center, Zamzam University College, Khartoum 11123, Sudan;
| | - Khalid Omer Alfarouk
- Research Center, Zamzam University College, Khartoum 11123, Sudan;
- Alfarouk Biomedical Research LLC, Temple Terrace, FL 33617, USA
- Hala Alfarouk Cancer Center, Khartoum 11123, Sudan
- Correspondence:
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Biochemical characterization of dihydroorotase of Leishmania donovani: Understanding pyrimidine metabolism through its inhibition. Biochimie 2016; 131:45-53. [DOI: 10.1016/j.biochi.2016.09.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Accepted: 09/15/2016] [Indexed: 11/22/2022]
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Ca-asp bound X-ray structure and inhibition of Bacillus anthracis dihydroorotase (DHOase). Bioorg Med Chem 2016; 24:4536-4543. [PMID: 27499369 DOI: 10.1016/j.bmc.2016.07.055] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/22/2016] [Accepted: 07/25/2016] [Indexed: 01/01/2023]
Abstract
Dihydroorotase (DHOase) is the third enzyme in the de novo pyrimidine synthesis pathway and is responsible for the reversible cyclization of carbamyl-aspartate (Ca-asp) to dihydroorotate (DHO). DHOase is further divided into two classes based on several structural characteristics, one of which is the length of the flexible catalytic loop that interacts with the substrate, Ca-asp, regulating the enzyme activity. Here, we present the crystal structure of Class I Bacillus anthracis DHOase with Ca-asp in the active site, which shows the peptide backbone of glycine in the shorter loop forming the necessary hydrogen bonds with the substrate, in place of the two threonines found in Class II DHOases. Despite the differences in the catalytic loop, the structure confirms that the key interactions between the substrate and active site residues are similar between Class I and Class II DHOase enzymes, which we further validated by mutagenesis studies. B. anthracis DHOase is also a potential antibacterial drug target. In order to identify prospective inhibitors, we performed high-throughput screening against several libraries using a colorimetric enzymatic assay and an orthogonal fluorescence thermal binding assay. Surface plasmon resonance was used for determining binding affinity (KD) and competition analysis with Ca-asp. Our results highlight that the primary difference between Class I and Class II DHOase is the catalytic loop. We also identify several compounds that can potentially be further optimized as potential B. anthracis inhibitors.
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The mononuclear metal center of type-I dihydroorotase from Aquifex aeolicus. BMC BIOCHEMISTRY 2013; 14:36. [PMID: 24314009 PMCID: PMC3880350 DOI: 10.1186/1471-2091-14-36] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Accepted: 10/28/2013] [Indexed: 01/22/2023]
Abstract
BACKGROUND Dihydroorotase (DHO) is a zinc metalloenzyme, although the number of active site zinc ions has been controversial. E. coli DHO was initially thought to have a mononuclear metal center, but the subsequent X-ray structure clearly showed two zinc ions, α and β, at the catalytic site. Aquifex aeolicus DHO, is a dodecamer comprised of six DHO and six aspartate transcarbamoylase (ATC) subunits. The isolated DHO monomer, which lacks catalytic activity, has an intact α-site and conserved β-site ligands, but the geometry of the second metal binding site is completely disrupted. However, the putative β-site is restored when the complex with ATC is formed and DHO activity is regained. Nevertheless, the X-ray structure of the complex revealed a single zinc ion at the active site. The structure of DHO from the pathogenic organism, S. aureus showed that it also has a single active site metal ion. RESULTS Zinc analysis showed that the enzyme has one zinc/DHO subunit and the addition of excess metal ion did not stimulate catalytic activity, nor alter the kinetic parameters. The metal free apoenzyme was inactive, but the full activity was restored upon the addition of one equivalent of Zn2+ or Co2+. Moreover, deletion of the β-site by replacing the His180 and His232 with alanine had no effect on catalysis in the presence or absence of excess zinc. The 2.2 Å structure of the double mutant confirmed that the β-site was eliminated but that the active site remained otherwise intact. CONCLUSIONS Thus, kinetically competent A. aeolicus DHO has a mononuclear metal center. In contrast, elimination of the putative second metal binding site in amidohydrolyases with a binuclear metal center, resulted in the abolition of catalytic activity. The number of active site metal ions may be a consideration in the design of inhibitors that selectively target either the mononuclear or binuclear enzymes.
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Truong L, Hevener KE, Rice AJ, Patel K, Johnson ME, Lee H. High-level expression, purification, and characterization of Staphylococcus aureus dihydroorotase (PyrC) as a cleavable His-SUMO fusion. Protein Expr Purif 2012; 88:98-106. [PMID: 23246866 DOI: 10.1016/j.pep.2012.11.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Revised: 11/21/2012] [Accepted: 11/29/2012] [Indexed: 01/29/2023]
Abstract
Staphylococcus aureus is a pathogenic bacterium that causes a variety of mild to lethal human diseases. The rapid spread of multidrug-resistant strains makes the discovery of new antimicrobial agents critical. Dihydroorotase (PyrC), the third enzyme in the bacterial pyrimidine biosynthesis pathway, is structurally and mechanistically distinct from its mammalian counterpart. It has been confirmed to be essential in S. aureus making it an attractive antibacterial drug target. No protocol to express and purify S. aureus PyrC (SaPyrC) has been reported. To obtain the SaPyrC enzyme and overcome anticipated solubility problems, the SaPyrC gene was cloned into the pET-SUMO vector. The N-terminal His-SUMO fused SaPyrC was expressed in Escherichia coli BL21 (DE3) with an HRV 3C protease recognition site inserted between the SUMO tag and SaPyrC to allow for improved cleavage by HRV protease. Purification of cleaved protein using HisTrap affinity and gel filtration columns resulted in native SaPyrC with estimated 95% purity and 40% yield. Both His-SUMO tagged and native SaPyrC form dimers, and enzyme characterization studies have shown that the His-SUMO tag affects enzyme activity slightly. Forward and reverse kinetic rate constants for both tagged and native SaPyrC were determined, and pH profiling studies revealed the optimal pH values for forward and reverse reactions.
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Affiliation(s)
- Lena Truong
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland Ave., Suite 3100, Chicago, IL 60607-7173, USA
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Novel insights for dihydroorotate dehydrogenase class 1A inhibitors discovery. Eur J Med Chem 2010; 45:5899-909. [DOI: 10.1016/j.ejmech.2010.09.055] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2010] [Revised: 09/21/2010] [Accepted: 09/23/2010] [Indexed: 11/22/2022]
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Dihydroorotase of human malarial parasite Plasmodium falciparum differs from host enzyme. Biochem Biophys Res Commun 2008; 366:821-6. [DOI: 10.1016/j.bbrc.2007.12.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2007] [Accepted: 12/05/2007] [Indexed: 10/22/2022]
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Li Y, Raushel FM. Inhibitors designed for the active site of dihydroorotase. Bioorg Chem 2005; 33:470-83. [PMID: 16213543 DOI: 10.1016/j.bioorg.2005.08.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2005] [Accepted: 08/20/2005] [Indexed: 11/23/2022]
Abstract
Four new compounds have been synthesized as potential inhibitors of dihydroorotase from Escherichia coli. NMR spectroscopy was used to show that 4,6-dioxo-piperidine-2(S)-carboxylic acid (3), exists in solution as a mixture of the hydrate (7), enol (8), and enolate (9) tautomeric forms. This compound was found to be a competitive inhibitor versus dihydroorotate and thio-dihydroorotate at pH values of 7-9. The K(i) of 76 microM was lowest at pH7.0 where the ketone and hydrate forms of the inhibitor 3 predominate in solution. Compound 3 was reduced to the two diastereomeric 4-hydroxy derivatives (4 and 5) and then dehydrated to yield the alkene derivative, 1,2,3,6-tetrahydro-6-oxopyridine-2(S)-carboxylic acid (6). Compounds 4-6 were competitive inhibitors versus thio-dihydroorotate at pH 8.0 with K(i) values of 3.0, 1.6, and 2.3 mM. Dihydroorotase was unable to dehydrate the 4-hydroxy derivative 4 or 5 to the alkene 6 or catalyze the reverse reaction.
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Affiliation(s)
- Yingchun Li
- Department of Chemistry, PO Box 30012, Texas A&M University, College Station, TX 77842-3012, USA
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9
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Hibbs DE, Overgaard J, Howard ST, Nguyen TH. Experimental charge density of a potential DHO synthetase inhibitor: dimethyl-trans-2-oxohexahydro-pyrimidine-4,6-dicarboxylate. Org Biomol Chem 2005; 3:441-7. [PMID: 15678181 DOI: 10.1039/b416118a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The experimental charge density distribution of dimethyl-trans-2-oxohexahydro-pyrimidine-4,6-dicarboxylate 1 has been determined using single-crystal X-ray diffraction data measured at 100 K, in terms of the rigid-pseudoatom formalism. Multipole refinement converged at R(F) = 0.034 for 7283 reflections with I > 3 sigma (I) and sin theta/lambda < or = 1.13 A(-1). Covalent and hydrogen bonding interactions are analyzed using a topological analysis of the Laplacian of the charge density. The experimentally derived electrostatic potential mapped onto the reactive surface of the molecule reveals the potential binding sites of 1.
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Affiliation(s)
- David E Hibbs
- Faculty of Pharmacy, University of Sydney, NSW 2006, Australia
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Ahuja A, Purcarea C, Ebert R, Sadecki S, Guy HI, Evans DR. Aquifex aeolicus dihydroorotase: association with aspartate transcarbamoylase switches on catalytic activity. J Biol Chem 2004; 279:53136-44. [PMID: 15381710 DOI: 10.1074/jbc.m403009200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dihydroorotase (DHOase) catalyzes the reversible condensation of carbamoyl aspartate to form dihydroorotate in de novo pyrimidine biosynthesis. The enzyme from Aquifex aeolicus, a hyperthermophilic organism of ancient lineage, was cloned and expressed in Escherichia coli. The purified protein was found to be a 45-kDa monomer containing a single zinc ion. Although there is no other DHOase gene in the A. aeolicus genome, the recombinant protein completely lacked catalytic activity at any temperature tested. However, DHOase formed an active complex with aspartate transcarbamoylase (ATCase) from the same organism. Whereas the k(cat) of 13.8 +/- 0.03 s(-1) was close to the value observed for the mammalian enzyme, the K (m)for dihydroorotate, 3.03 +/- 0.05 mM was 433-fold higher. Gel filtration and chemical cross-linking showed that the complex exists as a 240-kDa hexamer (DHO(3)-ATC(3)) and a 480-kDa duodecamer (DHO(6)-ATC(6)) probably in rapid equilibrium. Complex formation protects both DHOase and ATCase against thermal degradation at temperatures near 100 degrees C where the organism grows optimally. These results lead to the reclassification of both enzymes: ATCase, previously considered a Class C homotrimer, now falls into Class A, whereas the DHOase is a Class 1B enzyme. CD spectroscopy indicated that association with ATCase does not involve a significant perturbation of the DHOase secondary structure, but the visible absorption spectrum of a Co(2+)-substituted DHOase is appreciably altered upon complex formation suggesting a change in the electronic environment of the active site. The association of DHOase with ATCase probably serves as a molecular switch that ensures that free, uncomplexed DHOase in the cell remains inactive. At pH 7.4, the equilibrium ratio of carbamoyl aspartate to dihydroorotate is 17 and complex formation may drive the reaction in the biosynthetic direction.
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Affiliation(s)
- Anupama Ahuja
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, 540 E. Canfield St., Detroit, MI 48201, USA
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11
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Evans DR, Guy HI. Mammalian pyrimidine biosynthesis: fresh insights into an ancient pathway. J Biol Chem 2004; 279:33035-8. [PMID: 15096496 DOI: 10.1074/jbc.r400007200] [Citation(s) in RCA: 291] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- David R Evans
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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12
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Moffatt BA, Ashihara H. Purine and pyrimidine nucleotide synthesis and metabolism. THE ARABIDOPSIS BOOK 2002; 1:e0018. [PMID: 22303196 PMCID: PMC3243375 DOI: 10.1199/tab.0018] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- Barbara A. Moffatt
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
- Corresponding author,
, phone: 519-888-4567 ext 2517, fax: 519-746-0614
| | - Hiroshi Ashihara
- Department of Biology, Faculty of Science, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan
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Batty CA, Manthey MK, Kirk J, Manthey M, Christopherson RI, Hambley T. Synthesis and exchange reactions of 5-alkyl-2-oxo-6-thioxo-1,2,3,6-hexahydropyrimidine-4-carboxylic acids. J Heterocycl Chem 1997. [DOI: 10.1002/jhet.5570340444] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Affiliation(s)
- William N. Lipscomb
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138
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15
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Williams NK, Isaac EL, Peide Y, Christopherson RI. The catalytic mechanism of hamster dihydroorotase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 370:549-53. [PMID: 7660968 DOI: 10.1007/978-1-4615-2584-4_116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- N K Williams
- Department of Biochemistry, University of Sydney, NSW, Australia
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16
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Williams NK, O'Donoghue S, Christopherson RI. Homology and mutagenesis studies of hamster dihydroorotase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 370:597-601. [PMID: 7660976 DOI: 10.1007/978-1-4615-2584-4_124] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- N K Williams
- Department of Biochemistry, University of Sydney, NSW, Australia
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17
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Zimmermann BH, Kemling NM, Evans DR. Mutagenesis studies of conserved residues in mammalian dihydroorotase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 370:699-702. [PMID: 7661000 DOI: 10.1007/978-1-4615-2584-4_145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- B H Zimmermann
- Department of Biochemistry, University of Puerto Rico, San Juan 00936-5067
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Jahnke K, Podschun B, Schnackerz KD, Kautz J, Cook PF. Acid-base catalytic mechanism of dihydropyrimidinase from pH studies. Biochemistry 1993; 32:5160-6. [PMID: 8494893 DOI: 10.1021/bi00070a027] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pH dependence of kinetic parameters and solvent deuterium isotope effects have been used to probe the mechanism of the dihydropyrimidinase from the liver of pig and calf. The V/K for 5,6-dihydrouracil (DHU) (or the alternative substrate glutarimide) measured with either the native zinc or cadmium-substituted enzymes decreases at both low and high pH giving pK values of about 7.5-8 and 9-10. The low pK value observed in V is perturbed significantly to lower pH (approximately 6), and the high pK is not observed. The binding of glutarate monoamide is optimum when the group with a pK of 7.7 is protonated, and this same group must be protonated for the reverse reaction, that is, formation of DHU from N-carbamoyl-beta-alanine. These data are consistent with a general base mechanism and in addition suggest that the enzyme is present initially with a water bound to the active site zinc. The enzymic general base with a pK of 7.5-8 is required to activate water for nucleophilic attack on the C-4 of 5,6-dihydrouracil which is directly coordinated to the active site zinc. The second group with a pK of 9-10 likely reflects Zn-water ionization of the free enzyme. The water bound to the active site Zn is displaced by reactant binding, and thus the pK of 9-10 is not observed in the V profile. Solvent deuterium isotope effects are near unity on the V/K for the natural substrate 5,6-dihydrouracil, but a finite effect of 1.6 is observed on V.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- K Jahnke
- Theodor-Boveri-Institut fuer Biowissenschaften (Biozentrum), Universitaet Wuerzburg, Germany
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Krungkrai J, Krungkrai SR, Phakanont K. Antimalarial activity of orotate analogs that inhibit dihydroorotase and dihydroorotate dehydrogenase. Biochem Pharmacol 1992; 43:1295-301. [PMID: 1348618 DOI: 10.1016/0006-2952(92)90506-e] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dihydroorotase and dihydroorotate dehydrogenase, two enzymes of the pyrimidine biosynthetic pathway, were purified from Plasmodium berghei to apparent homogeneity. Orotate and a series of 5-substituted derivatives were found to inhibit competitively the purified enzymes from the malaria parasite. The order of effectiveness as inhibitors on pyrimidine ring cleavage reaction for dihydroorotase was 5-fluoro orotate greater than 5-amino orotate, 5-methyl orotate greater than orotate greater than 5-bromo orotate greater than 5-iodo orotate with Ki values of 65, 142, 166, 860, 2200 and greater than 3500 microM, respectively. 5-Fluoro orotate and orotate were the most effective inhibitors for dihydroorotate dehydrogenase. In vitro, 5-fluoro orotate and 5-amino orotate caused 50% inhibition of the growth of P. falciparum at concentrations of 10 nM and 1 microM, respectively. In mice infected with P. berghei, these two orotate analogs at a dose of 25 mg/kg body weight eliminated parasitemia after a 4-day treatment, an effect comparable to that of the same dose of chloroquine. The infected mice treated with 5-fluoro orotate at a lower dose of 2.5 mg/kg had a 95% reduction in parasitemia. The effects of the more potent compounds tested in combination with inhibitors of other enzymes of this pathway on P. falciparum in vitro and P. berghei in vivo are currently under investigation. These results suggest that the pyrimidine biosynthetic pathway in the malarial parasite may be a target for the design of antimalarial drugs.
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Affiliation(s)
- J Krungkrai
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
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20
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Brown DC, Collins KD. Dihydroorotase from Escherichia coli. Substitution of Co(II) for the active site Zn(II). J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52336-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Williams NK, Simpson RJ, Moritz RL, Peide Y, Crofts L, Minasian E, Leach SJ, Wake RG, Christopherson RI. Location of the dihydroorotase domain within trifunctional hamster dihydroorotate synthetase. Gene X 1990; 94:283-8. [PMID: 1979549 DOI: 10.1016/0378-1119(90)90399-c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mammalian dihydroorotase (DHOase, EC 3.5.2.3) is part of a trifunctional protein, dihydroorotate synthetase which catalyzes the first three reactions of de novo pyrimidine biosynthesis. We have subcloned a portion of the cDNA from the plasmid pCAD142 and obtained a nucleotide sequence which extends 2.1 kb in the 5' direction from the sequence encoding the aspartate transcarbamoylase (ATCase) domain at the 3'-end of the cDNA. The DHOase and ATCase domains have been purified from an elastase digest of the trifunctional protein and subjected to amino acid (aa) sequencing from their N termini. The sequence of the N-terminal 24 aa of the DHOase domain has been obtained and aligned with the cDNA sequence. The C-terminal residues of the DHOase domain have been identified as Leu followed by Val which, when taken with partial sequences of the CNBr fragments of this domain, defines the coding sequence of the active, globular DHOase domain released by proteolysis. Prediction of protein secondary structure from the deduced aa sequence showed that the DHOase domain (Mr 37,751) is separated from the C-terminal ATCase domain (Mr 34,323) by a bridging sequence (Mr 12,532) consisting of multiple beta-turns.
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Affiliation(s)
- N K Williams
- Department of Biochemistry, University of Sydney, New South Wales, Australia
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22
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Christopherson RI, Lyons SD. Potent inhibitors of de novo pyrimidine and purine biosynthesis as chemotherapeutic agents. Med Res Rev 1990; 10:505-48. [PMID: 2243513 DOI: 10.1002/med.2610100406] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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23
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Mehdi S, Wiseman JS. An assay for dihydroorotase using high-performance liquid chromatography with radioactivity detection. Anal Biochem 1989; 176:105-8. [PMID: 2565694 DOI: 10.1016/0003-2697(89)90279-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
An assay for measuring dihydroorotase activity was devised. Radiolabeled substrate and product were separated by high-performance liquid chromatography using a reverse-phase column with ion-pairing, and the radioactivity was quantitated by flow detection.
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Affiliation(s)
- S Mehdi
- Merrell Dow Research Institute, Cincinnati, Ohio 45215
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Kelly RE, Mally MI, Evans DR. The dihydroorotase domain of the multifunctional protein CAD. Subunit structure, zinc content, and kinetics. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)38494-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Pettigrew DW, Mehta BJ, Bidigare RR, Choudhury RR, Scheffler JE, Sander EG. Enzyme elements involved in the interconversion of L-carbamylaspartate and L-dihydroorotate by dihydroorotase from Clostridium oroticum. Arch Biochem Biophys 1985; 243:447-53. [PMID: 2867744 DOI: 10.1016/0003-9861(85)90521-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Enzyme elements that are involved in the reversible cyclization of L-carbamylaspartate to L-dihdroorotate catalyzed by dihydroorotase (EC 3.5.2.3) from Clostridium oroticum (ATCC 25750) have been studied. Removal of Zn(II) from the enzyme by chelators followed by incubation of apoenzyme with Co(II) results in replacement of two to three of the four Zn(II) ions per molecule by Co(II). The catalytic properties of the Zn(II)Co(II) dihydroorotase are different from those of native enzyme. The Vmax is increased for both the synthesis and hydrolysis of L-dihydroorotate. The Km for L-dihydroorotate is unchanged, while the Km for L-carbamylaspartate is increased more than twofold. On the other hand, the kinetic properties of Zn(II)-reconstituted dihydroorotase are indistinguishable from those of native enzyme. The pH dependence of Vmax is also altered by the Co(II) substitution. For both Zn(II)- and Zn(II)Co(II)-dihydroorotase, this pH dependence is well described by a single ionization and the pK's for L-dihydroorotate synthesis and hydrolysis are different. Substitution with Co(II) increases the pK for both reaction directions to different extents. These results strongly support a role for the tightly bound metals in the catalytic mechanism. In addition, diethylpyrocarbonate rapidly inactivates the enzyme. The inactivation is prevented by L-dihydroorotate. This result is consistent with a role for at least one histidine in catalysis. The possibility that C. oroticum dihydroorotase may be useful model for the more complex mammalian enzyme is considered.
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Grayson DR, Evans DR. The isolation and characterization of the aspartate transcarbamylase domain of the multifunctional protein, CAD. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32593-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Christopherson RI, Yu ML, Jones ME. An overall radioassay for the first three reactions of de novo pyrimidine biosynthesis. Anal Biochem 1981; 111:240-9. [PMID: 6113788 DOI: 10.1016/0003-2697(81)90560-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Kensler TW, Han N, Cooney DA. A straightforward method for the simultaneous preparation of radiolabeled L-dihydroörotic and N-carbamyl-L-aspartic acids. Anal Biochem 1981; 111:49-53. [PMID: 7235240 DOI: 10.1016/0003-2697(81)90226-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Christopherson RI, Traut TW, Jones ME. Multienzymatic proteins in mammalian pyrimidine biosynthesis: channeling of intermediates to avoid futile cycles. CURRENT TOPICS IN CELLULAR REGULATION 1981; 18:59-77. [PMID: 7023859 DOI: 10.1016/b978-0-12-152818-8.50010-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Kensler TW, Cooney DA. Chemotherapeutic inhibitors of the enzymes of the de novo pyrimidine pathway. ADVANCES IN PHARMACOLOGY AND CHEMOTHERAPY 1981; 18:273-352. [PMID: 6119898 DOI: 10.1016/s1054-3589(08)60257-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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