1
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Bearne SL. Capturing the free energy of transition state stabilization: insights from the inhibition of mandelate racemase. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220041. [PMID: 36633273 PMCID: PMC9835602 DOI: 10.1098/rstb.2022.0041] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mandelate racemase (MR) catalyses the Mg2+-dependent interconversion of (R)- and (S)-mandelate. To effect catalysis, MR stabilizes the altered substrate in the transition state (TS) by approximately 26 kcal mol-1 (-ΔGtx), such that the upper limit of the virtual dissociation constant of the enzyme-TS complex is 2 × 10-19 M. Designing TS analogue inhibitors that capture a significant amount of ΔGtx for binding presents a challenge since there are a limited number of protein binding determinants that interact with the substrate and the structural simplicity of mandelate constrains the number of possible isostructural variations. Indeed, current intermediate/TS analogue inhibitors of MR capture less than or equal to 30% of ΔGtx because they fail to fully capitalize on electrostatic interactions with the metal ion, and the strength and number of all available electrostatic and H-bond interactions with binding determinants present at the TS. Surprisingly, phenylboronic acid (PBA), 2-formyl-PBA, and para-chloro-PBA capture 31-38% of ΔGtx. The boronic acid group interacts with the Mg2+ ion and multiple binding determinants that effect TS stabilization. Inhibitors capable of forming multiple interactions can exploit the cooperative interactions that contribute to optimum binding of the TS. Hence, maximizing interactions with multiple binding determinants is integral to effective TS analogue inhibitor design. This article is part of the theme issue 'Reactivity and mechanism in chemical and synthetic biology'.
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Affiliation(s)
- Stephen L. Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2,Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
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2
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Blériot Y, Auberger N, Désiré J. Sugar-Derived Amidines and Congeners: Structures, Glycosidase Inhibition and Applications. Curr Med Chem 2021; 29:1271-1292. [PMID: 34951354 DOI: 10.2174/0929867329666211222164545] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/16/2021] [Accepted: 10/22/2021] [Indexed: 11/22/2022]
Abstract
Glycosidases, the enzymes responsible for the breakdown of glycoconjugates including di-, oligo- and polysaccharides are ubiquitous through all kingdoms of life. The extreme chemical stability of the glycosidic bond combined with the catalytic rates achieved by glycosidases makes them among the most proficient of all enzymes.
Given their multitude of roles in vivo, inhibition of these enzymes is highly attractive with potential in the treatment of a vast array of pathologies ranging from lysosomal storage and diabetes to viral infections. Therefore great efforts have been invested in the last three decades to design and synthesize inhibitors of glycosidases leading to a number of drugs currently on the market. Amongst the vast array of structures that have been disclosed, sugars incorporating an amidine moiety have been the focus of many research groups around the world because of their glycosidase transition state-like structure. In this review we report and discuss the structure, the inhibition profile and the use of these molecules including related structural congeners as transition state analogs.
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Affiliation(s)
- Yves Blériot
- Université de Poitiers, IC2MP, UMR CNRS 7285, Equipe "OrgaSynth", Groupe Glycochimie 4 rue Michel Brunet, 86073 Poitiers cedex 9. France
| | - Nicolas Auberger
- Université de Poitiers, IC2MP, UMR CNRS 7285, Equipe "OrgaSynth", Groupe Glycochimie 4 rue Michel Brunet, 86073 Poitiers cedex 9. France
| | - Jérôme Désiré
- Université de Poitiers, IC2MP, UMR CNRS 7285, Equipe "OrgaSynth", Groupe Glycochimie 4 rue Michel Brunet, 86073 Poitiers cedex 9. France
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3
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Adesina AS, Luk LYP, Allemann RK. Cryo-kinetics Reveal Dynamic Effects on the Chemistry of Human Dihydrofolate Reductase. Chembiochem 2021; 22:2410-2414. [PMID: 33876533 PMCID: PMC8360168 DOI: 10.1002/cbic.202100017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 04/16/2021] [Indexed: 12/03/2022]
Abstract
Effects of isotopic substitution on the rate constants of human dihydrofolate reductase (HsDHFR), an important target for anti-cancer drugs, have not previously been characterized due to its complex fast kinetics. Here, we report the results of cryo-measurements of the kinetics of the HsDHFR catalyzed reaction and the effects of protein motion on catalysis. Isotopic enzyme labeling revealed an enzyme KIE (kHLE /kHHE ) close to unity above 0 °C; however, the enzyme KIE was increased to 1.72±0.15 at -20 °C, indicating that the coupling of protein motions to the chemical step is minimized under optimal conditions but enhanced at non-physiological temperatures. The presented cryogenic approach provides an opportunity to probe the kinetics of mammalian DHFRs, thereby laying the foundation for characterizing their transition state structure.
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Affiliation(s)
| | - Louis Y. P. Luk
- School of ChemistryCardiff UniversityPark PlaceCardiffCF10 3ATUK
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4
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Mhashal AR, Major DT. Temperature-Dependent Kinetic Isotope Effects in R67 Dihydrofolate Reductase from Path-Integral Simulations. J Phys Chem B 2021; 125:1369-1377. [PMID: 33522797 PMCID: PMC7883348 DOI: 10.1021/acs.jpcb.0c10318] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/05/2021] [Indexed: 11/28/2022]
Abstract
Calculation of temperature-dependent kinetic isotope effects (KIE) in enzymes presents a significant theoretical challenge. Additionally, it is not trivial to identify enzymes with available experimental accurate intrinsic KIEs in a range of temperatures. In the current work, we present a theoretical study of KIEs in the primitive R67 dihydrofolate reductase (DHFR) enzyme and compare with experimental work. The advantage of R67 DHFR is its significantly lower kinetic complexity compared to more evolved DHFR isoforms. We employ mass-perturbation-based path-integral simulations in conjunction with umbrella sampling and a hybrid quantum mechanics-molecular mechanics Hamiltonian. We obtain temperature-dependent KIEs in good agreement with experiments and ascribe the temperature-dependent KIEs primarily to zero-point energy effects. The active site in the primitive enzyme is found to be poorly preorganized, which allows excessive water access to the active site and results in loosely bound reacting ligands.
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Affiliation(s)
- Anil R. Mhashal
- Department of Chemistry and Institute
for Nanotechnology & Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Dan Thomas Major
- Department of Chemistry and Institute
for Nanotechnology & Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
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5
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Nallar M, Wong HW. Hydroxyl Group Stabilization for Increased Yields of Low-Molecular-Weight Products in the Copyrolysis of Cellulose and Thermoplastics. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.9b01177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Melisa Nallar
- Department of Chemical Engineering, University of Massachusetts Lowell, One University Avenue, Lowell, Massachusetts 01854, United States
| | - Hsi-Wu Wong
- Department of Chemical Engineering, University of Massachusetts Lowell, One University Avenue, Lowell, Massachusetts 01854, United States
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6
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Abstract
Transition state theory teaches that chemically stable mimics of enzymatic transition states will bind tightly to their cognate enzymes. Kinetic isotope effects combined with computational quantum chemistry provides enzymatic transition state information with sufficient fidelity to design transition state analogues. Examples are selected from various stages of drug development to demonstrate the application of transition state theory, inhibitor design, physicochemical characterization of transition state analogues, and their progress in drug development.
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Affiliation(s)
- Vern L. Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
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7
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Harris ME, York DM, Piccirilli JA, Anderson VE. Kinetic Isotope Effect Analysis of RNA 2′- O -Transphosphorylation. Methods Enzymol 2017; 596:433-457. [DOI: 10.1016/bs.mie.2017.07.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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8
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Linscott JA, Kapilashrami K, Wang Z, Senevirathne C, Bothwell IR, Blum G, Luo M. Kinetic isotope effects reveal early transition state of protein lysine methyltransferase SET8. Proc Natl Acad Sci U S A 2016; 113:E8369-E8378. [PMID: 27940912 PMCID: PMC5206543 DOI: 10.1073/pnas.1609032114] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Protein lysine methyltransferases (PKMTs) catalyze the methylation of protein substrates, and their dysregulation has been linked to many diseases, including cancer. Accumulated evidence suggests that the reaction path of PKMT-catalyzed methylation consists of the formation of a cofactor(cosubstrate)-PKMT-substrate complex, lysine deprotonation through dynamic water channels, and a nucleophilic substitution (SN2) transition state for transmethylation. However, the molecular characters of the proposed process remain to be elucidated experimentally. Here we developed a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) method and corresponding mathematic matrix to determine precisely the ratios of isotopically methylated peptides. This approach may be generally applicable for examining the kinetic isotope effects (KIEs) of posttranslational modifying enzymes. Protein lysine methyltransferase SET8 is the sole PKMT to monomethylate histone 4 lysine 20 (H4K20) and its function has been implicated in normal cell cycle progression and cancer metastasis. We therefore implemented the MS-based method to measure KIEs and binding isotope effects (BIEs) of the cofactor S-adenosyl-l-methionine (SAM) for SET8-catalyzed H4K20 monomethylation. A primary intrinsic 13C KIE of 1.04, an inverse intrinsic α-secondary CD3 KIE of 0.90, and a small but statistically significant inverse CD3 BIE of 0.96, in combination with computational modeling, revealed that SET8-catalyzed methylation proceeds through an early, asymmetrical SN2 transition state with the C-N and C-S distances of 2.35-2.40 Å and 2.00-2.05 Å, respectively. This transition state is further supported by the KIEs, BIEs, and steady-state kinetics with the SAM analog Se-adenosyl-l-selenomethionine (SeAM) as a cofactor surrogate. The distinct transition states between protein methyltransferases present the opportunity to design selective transition-state analog inhibitors.
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Affiliation(s)
- Joshua A Linscott
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
- Program of Pharmacology, Weill Graduate School of Medical Science, Cornell University, New York, NY 10021
| | - Kanishk Kapilashrami
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Zhen Wang
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Chamara Senevirathne
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Ian R Bothwell
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Gil Blum
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Minkui Luo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065;
- Program of Pharmacology, Weill Graduate School of Medical Science, Cornell University, New York, NY 10021
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9
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Characterization of inosine–uridine nucleoside hydrolase (RihC) from Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:656-62. [DOI: 10.1016/j.bbapap.2014.01.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 01/12/2014] [Accepted: 01/17/2014] [Indexed: 11/19/2022]
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10
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Liuni P, Olkhov-Mitsel E, Orellana A, Wilson DJ. Measuring kinetic isotope effects in enzyme reactions using time-resolved electrospray mass spectrometry. Anal Chem 2013; 85:3758-64. [PMID: 23461634 DOI: 10.1021/ac400191t] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Kinetic isotope effect (KIE) measurements are a powerful tool for studying enzyme mechanisms; they can provide insights into microscopic catalytic processes and even structural constraints for transition states. However, KIEs have not come into widespread use in enzymology, due in large part to the requirement for prohibitively cumbersome experimental procedures and daunting analytical frameworks. In this work, we introduce time-resolved electrospray ionization mass spectrometry (TRESI-MS) as a straightforward, precise, and inexpensive method for measuring KIEs. Neither radioisotopes nor large amounts of material are needed and kinetic measurements for isotopically "labeled" and "unlabeled" species are acquired simultaneously in a single "competitive" assay. The approach is demonstrated first using a relatively large isotope effect associated with yeast alcohol dehydrogenase (YADH) catalyzed oxidation of ethanol. The measured macroscopic KIE of 2.19 ± 0.05 is consistent with comparable measurements in the literature but cannot be interpreted in a way that provides insights into isotope effects in individual microscopic steps. To demonstrate the ability of TRESI-MS to directly measure intrinsic KIEs and to characterize the precision of the technique, we measure a much smaller (12)C/(13)C KIE associated specifically with presteady state acylation of chymotrypsin during hydrolysis of an ester substrate.
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Affiliation(s)
- Peter Liuni
- Department of Chemistry, York University, Toronto, ON, Canada
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11
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Ansari MY, Dikhit MR, Sahoo GC, Das P. Comparative modeling of HGPRT enzyme of L. donovani and binding affinities of different analogs of GMP. Int J Biol Macromol 2012; 50:637-49. [PMID: 22327112 DOI: 10.1016/j.ijbiomac.2012.01.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/05/2012] [Accepted: 01/10/2012] [Indexed: 11/28/2022]
Abstract
Hypoxanthine-guanine phosphoribosyl transferase (HGPRT; EC 2.4.2.8) is a central enzyme in the purine recycling pathway. Parasitic protozoa (Leishmania donovani) cannot synthesize purines de novo and utilize the salvage pathway to produce purine bases. Thus, this enzyme is targeted in drug discovery and development. The model of the monomeric L. donovani HGPRT showed that this enzyme is an α/β type protein with a PRTase type I folding pattern. Among all of the computationally screened compounds, pentamidine, 1,3-dinitroadamantane, acyclovir and analogs of acyclovir had higher binding affinities than the real substrate (guanosine monophosphate). Amino acids of HGPRT that are frequently involved in the binding of these compounds are Lys 66, Asp 74, Arg 77, Asp 81, Val 88, Tyr 182, Arg 192 and Arg 194. It is predicted that patients suffering from both HIV and visceral leishmaniasis (VL) may benefit if they are treated with acyclovir or pentamidine in conjunction with first-line antileishmanial therapies such as miltefosine and AmBisome.
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Affiliation(s)
- Md Yousuf Ansari
- BioMedical Informatics Division, Rajendra Memorial Research Institute of Medical Sciences, Agam Kuan, Patna 800007, India
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12
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Wang S, Lim J, Thomas K, Yan F, Angeletti RH, Schramm VL. A complex of methylthioadenosine/S-adenosylhomocysteine nucleosidase, transition state analogue, and nucleophilic water identified by mass spectrometry. J Am Chem Soc 2012; 134:1468-70. [PMID: 22239413 DOI: 10.1021/ja211176q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An enzyme-stabilized nucleophilic water molecule has been implicated at the transition state of Escherichia coli methylthioadenosine nucleosidase (EcMTAN) by transition state analysis and crystallography. We analyzed the EcMTAN mass in complex with a femtomolar transition state analogue to determine whether the inhibitor and nucleophilic water could be detected in the gas phase. EcMTAN-inhibitor and EcMTAN-inhibitor-nucleophilic water complexes were identified by high-resolution mass spectrometry under nondenaturing conditions. The enzyme-inhibitor-water complex is sufficiently stable to exist in the gas phase.
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Affiliation(s)
- Shanzhi Wang
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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13
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Qi J, Virga KG, Das S, Zhao Y, Yun MK, White SW, Lee RE. Synthesis of bi-substrate state mimics of dihydropteroate synthase as potential inhibitors and molecular probes. Bioorg Med Chem 2010; 19:1298-305. [PMID: 21216602 DOI: 10.1016/j.bmc.2010.12.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 11/25/2010] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
Abstract
The increasing emergence of resistant bacteria drives us to design and develop new antimicrobial agents. Pursuant to that goal, a new targeting approach of the dihydropteroate synthase enzyme, which serves as the site of action for the sulfonamide class of antimicrobial agents, is being explored. Using structural information, a new class of transition state mimics has been designed and synthesized that have the capacity to bind to the pterin, phosphate and para-amino binding sites. The design, synthesis and evaluation of these compounds as inhibitors of Bacillusanthracis dihydropteroate synthase is described herein. Outcomes from this work have identified the first trivalent inhibitors of dihydropteroate synthase whose activity displayed slow binding inhibition. The most active compounds in this series contained an oxidized pterin ring. The binding of these inhibitors was modeled into the dihydropteroate synthase active site and demonstrated a good correlation with the observed bioassay data, as well as provided important insight for the future design of higher affinity transition state mimics.
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Affiliation(s)
- Jianjun Qi
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, 847 Monroe Ave., Rm327, Memphis, TN 38613, USA
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14
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Pícha J, Buděšínský M, Fiedler P, Sanda M, Jiráček J. Synthesis of α-carboxyphosphinopeptides derived from norleucine. Amino Acids 2010; 39:1265-80. [PMID: 20349321 DOI: 10.1007/s00726-010-0561-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Accepted: 03/09/2010] [Indexed: 11/25/2022]
Abstract
In the present study, we describe in detail the synthesis of a relatively rare class of phosphorus compounds, α-carboxyphosphinopeptides. We prepared several norleucine-derived α-carboxyphosphinic pseudopeptides of the general formula Nle-Ψ[PO(OH)]-Gly. These compounds could have important applications as transition state-mimicking inhibitors for methionine or leucine aminopeptidases or other enzymes. For the preparation of the key α-carboxyphosphinate protected precursors, we investigated, compared and improved two different synthetic methods described in literature: the Arbuzov reaction of a silylated N-protected phosphinic acid with a bromoacetate ester and the nucleophilic addition of a mixed O-methyl S-phenyl N-protected phosphonic acid or a methyl N-protected phosphonochloridate with tert-butyl lithioacetate. We also prepared two N-Fmoc protected synthons, Fmoc-Nle-Ψ[PO(OH)]-Gly-COOH and Fmoc-Nle-Ψ[PO(OAd)]-Gly-COOH, and demonstrated that these precursors are suitable building blocks for the solid-phase synthesis of α-carboxyphosphinopeptides.
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Affiliation(s)
- Jan Pícha
- Institute of Organic Chemistry and Biochemistry, v. v. i., Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 166 10, Prague 6, Czech Republic
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15
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Pícha J, Buděšínský M, Hančlová I, Šanda M, Fiedler P, Vaněk V, Jiráček J. Efficient synthesis of phosphonodepsipeptides derived from norleucine. Tetrahedron 2009. [DOI: 10.1016/j.tet.2009.05.051] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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Vanek V, Budesínský M, Kabeleová P, Sanda M, Kozísek M, Hanclová I, Mládková J, Brynda J, Rosenberg I, Koutmos M, Garrow TA, Jirácek J. Structure-activity study of new inhibitors of human betaine-homocysteine S-methyltransferase. J Med Chem 2009; 52:3652-65. [PMID: 19534555 DOI: 10.1021/jm8015798] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Betaine-homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to l-homocysteine, yielding dimethylglycine and l-methionine. In this study, we prepared a new series of BHMT inhibitors. The inhibitors were designed to mimic the hypothetical transition state of BHMT substrates and consisted of analogues with NH, N(CH(3)), or N(CH(3))(2) groups separated from the homocysteine sulfur atom by a methylene, ethylene, or a propylene spacer. Only the inhibitor with the N(CH(3)) moiety and ethylene spacer gave moderate inhibition. This result led us to prepare two inhibitors lacking a nitrogen atom in the S-linked alkyl chain: (RS,RS)-5-(3-amino-3-carboxypropylthio)-3-methylpentanoic acid and (RS)-5-(3-amino-3-carboxypropylthio)-3,3-dimethylpentanoic acid. Both of these compounds were highly potent inhibitors of BHMT. The finding that BHMT does not tolerate a true betaine mimic within these inhibitors, especially the nitrogen atom, is surprising and evokes questions about putative conformational changes of BHMT upon the binding of the substrates/products and inhibitors.
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Affiliation(s)
- Václav Vanek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
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17
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Porcelli M, Concilio L, Peluso I, Marabotti A, Facchiano A, Cacciapuoti G. Pyrimidine-specific ribonucleoside hydrolase from the archaeon Sulfolobus solfataricus- biochemical characterization and homology modeling. FEBS J 2008; 275:1900-14. [DOI: 10.1111/j.1742-4658.2008.06348.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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18
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Abstract
Various 4'-F nucleosides have been prepared in only two to three steps via sequential bromination and fluorination of ribofuranoses or nucleosides.
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Affiliation(s)
- Seongmin Lee
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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19
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Berti PJ, McCann JAB. Toward a detailed understanding of base excision repair enzymes: transition state and mechanistic analyses of N-glycoside hydrolysis and N-glycoside transfer. Chem Rev 2006; 106:506-55. [PMID: 16464017 DOI: 10.1021/cr040461t] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Paul J Berti
- Department of Chemistry, McMaster University, Hamilton, Ontario, Canada.
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20
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Bates C, Kendrick Z, McDonald N, Kline PC. Transition state analysis of adenosine nucleosidase from yellow lupin (Lupinus luteus). PHYTOCHEMISTRY 2006; 67:5-12. [PMID: 16300810 DOI: 10.1016/j.phytochem.2005.10.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Revised: 08/24/2005] [Indexed: 05/05/2023]
Abstract
The transition state of adenosine nucleosidase (EC 3.2.2.7) isolated from yellow lupin (Lupinus luteus) was determined based upon a series of heavy atom kinetic isotope effects. Adenosine labeled with 13C, 2H, and 15N was analyzed by liquid chromatography/electrospray mass spectrometry to determine kinetic isotope effects. Values of 1.024+/-0.004, 1.121+/-0.005, 1.093+/-0.004, 0.993+/-0.006, and 1.028+/-0.005 were found for [1'-13C], [1'-2H], [2'-2H], [5'-2H], and [9-15N] adenosine, respectively. Using a bond order bond energy vibrational analysis, a transition state consisting of a significantly broken C-N bond, formation of an oxocarbenium ion in the ribose ring, a conformation of C3-exo for the ribose ring, and protonation of the heterocyclic base was proposed. This transition state was found to be very similar to the transition state for nucleoside hydrolase, another purine metabolizing enzyme, isolated from Crithidia fasciculata.
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Affiliation(s)
- Carl Bates
- Department of Chemistry, Middle Tennessee State University (MTSU), Box 68, Murfreesboro, TN 37132, USA
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21
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Hunt C, Gillani N, Farone A, Rezaei M, Kline PC. Kinetic isotope effects of nucleoside hydrolase from Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2005; 1751:140-9. [PMID: 16027052 DOI: 10.1016/j.bbapap.2005.06.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Revised: 06/01/2005] [Accepted: 06/02/2005] [Indexed: 11/25/2022]
Abstract
rihC is one of a group of three ribonucleoside hydrolases found in Escherichia coli (E. coli). The enzyme catalyzes the hydrolysis of selected nucleosides to ribose and the corresponding base. A family of Vmax/Km kinetic isotope effects using uridine labeled with stable isotopes, such as 2H, 13C, and 15N, were determined by liquid chromatography/mass spectrometry (LC/MS). The kinetic isotope effects were 1.012+/-0.006, 1.027+/-0.005, 1.134+/-0.007, 1.122+/-0.008, and 1.002+/-0.004 for [1'-13C], [1-15N], [1'-2H], [2'-2H], and [5'-2H2] uridine, respectively. A transition state based upon a bond-energy bond-order vibrational analysis (BEBOVIB) of the observed kinetic isotope effects is proposed. The main features of this transition state are activation of the heterocyclic base by protonation of/or hydrogen bonding to O2, an extensively broken C-N glycosidic bond, formation of an oxocarbenium ion in the ribose ring, C3'-exo ribose ring conformation, and almost no bond formation to the attacking nucleophile. The proposed transition state for the prokaryotic E. coli nucleoside hydrolase is compared to that of a similar enzyme isolated from Crithidia fasciculata (C. fasciculata).
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Affiliation(s)
- Cindy Hunt
- Department of Chemistry, Middle Tennessee State University, Box 68, Murfreesboro, TN 37132, USA
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22
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Liu HY, Wang Z, Regni C, Zou X, Tipton PA. Detailed Kinetic Studies of an Aggregating Inhibitor; Inhibition of Phosphomannomutase/Phosphoglucomutase by Disperse Blue 56†. Biochemistry 2004; 43:8662-9. [PMID: 15236574 DOI: 10.1021/bi0491907] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phosphomannomutase/phosphoglucomutase occupies a central position in the pathways by which several virulence factors are synthesized in Pseudomonas aeruginosa. Virtual screening was used to identify potential inhibitors of phosphomannomutase/ phosphoglucomutase, and one compound, the anthraquinone-based dye Disperse Blue 56, showed potent inhibition in vitro. The kinetics of inhibition was complex; the time courses for reactions in the presence of the inhibitor were biphasic, suggestive of slow-binding inhibition. Quantitative analysis of the progress curves and preincubation experiments demonstrated that slow-binding inhibition was not occurring, however. Initial velocity kinetic studies indicated that Disperse Blue 56 was a parabolic, noncompetitve inhibitor. Progress curves for reactions in the presence of Disperse Blue 56 could be fitted very well by a model in which 2 equiv of the inhibitor bound to free enzyme or the enzyme-substrate complex. The inhibition was largely relieved by the inclusion of 0.01% Triton X-100 in the assay solutions, which has been suggested to be the hallmark for inhibition by compounds that exert their effect through aggregates [McGovern, S. L., Caselli, E., Grigorieff, N., and Shiochet, B. K. (2002) J. Med. Chem. 45, 1712-1722]. Our kinetic data appear to be consistent with either inhibition by a dimer of Disperse Blue 56 or inhibition by a Disperse Blue 56 aggregate, but the latter appears much more likely. We present a detailed analysis of the system to provide further information that may help in the recognition of inhibition through aggregation.
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Affiliation(s)
- Hao-Yang Liu
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65211, USA
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23
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Lewandowicz A, Schramm VL. Transition state analysis for human and Plasmodium falciparum purine nucleoside phosphorylases. Biochemistry 2004; 43:1458-68. [PMID: 14769022 DOI: 10.1021/bi0359123] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent studies have shown that Plasmodium falciparum is sensitive to a purine salvage block at purine nucleoside phosphorylase (PNP) and that human PNP is a target for T-cell proliferative diseases. Specific tight-binding inhibitors might be designed on the basis of specific PNP transition state structures. Kinetic isotope effects (KIEs) were measured for arsenolysis of inosine catalyzed by P. falciparum and human purine nucleoside phosphorylases. Intrinsic KIEs from [1'-(3)H]-, [2'-(3)H]-, [1'-(14)C]-, [9-(15)N]-, and [5'-(3)H]inosines were 1.184 +/- 0.004, 1.031 +/- 0.004, 1.002 +/- 0.006, 1.029 +/- 0.006, and 1.062 +/- 0.002 for the human enzyme and 1.116 +/- 0.007, 1.036 +/- 0.003, 0.996 +/- 0.006, 1.019 +/- 0.005, and 1.064 +/- 0.003 for P. falciparum PNPs, respectively. Analysis of KIEs indicated a highly dissociative D(N)A(N) (S(N)1) stepwise mechanism with very little leaving group involvement. The near-unity 1'-(14)C KIEs for both human and P. falciparum PNP agree with the theoretical value for a 1'-(14)C equilibrium isotope effect for oxacarbenium ion formation when computed at the B1LYP/6-31G(d) level of theory. The 9-(15)N KIE for human PNP is also in agreement with theory for equilibrium formation of hypoxanthine and oxacarbenium ion at this level of theory. The 9-(15)N KIE for P. falciparum PNP shows a constrained vibrational environment around N9 at the transition state. A relatively small beta-secondary 2'-(3)H KIE for both enzymes indicates a 3'-endo conformation for ribose and relatively weak hyperconjugation at the transition state. The large 5'-(3)H KIE reveals substantial distortion at the 5'-hydroxymethyl group which causes loosening of the C5'-H5' bonds during the reaction coordinate.
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Affiliation(s)
- Andrzej Lewandowicz
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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24
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Evans GB. The Synthesis of N-Ribosyl Transferase Inhibitors Based on a Transition State Blueprint. Aust J Chem 2004. [DOI: 10.1071/ch04112] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A quarter of a century ago transition state analysis and transition state analogue design promised the prospect of extraordinarily potent enzyme inhibitors. The present overview describes the transition state analysis of a variety of N-ribosyl transferases, the design and synthesis of extremely powerful transition state analogue inhibitors of these nucleoside processing enzymes, and their current therapeutic uses and potentials.
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25
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Bruner SD, Norman DP, Fromme JC, Verdine GL. Structural and mechanistic studies on repair of 8-oxoguanine in mammalian cells. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 65:103-11. [PMID: 12760025 DOI: 10.1101/sqb.2000.65.103] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- S D Bruner
- Departments of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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26
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Bell AF, Feng Y, Hofstein HA, Parikh S, Wu J, Rudolph MJ, Kisker C, Whitty A, Tonge PJ. Stereoselectivity of enoyl-CoA hydratase results from preferential activation of one of two bound substrate conformers. CHEMISTRY & BIOLOGY 2002; 9:1247-55. [PMID: 12445775 DOI: 10.1016/s1074-5521(02)00263-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Enoyl-CoA hydratase catalyzes the hydration of trans-2-crotonyl-CoA to 3(S)- and 3(R)-hydroxybutyryl-CoA with a stereoselectivity (3(S)/3(R)) of 400,000 to 1. Importantly, Raman spectroscopy reveals that both the s-cis and s-trans conformers of the substrate analog hexadienoyl-CoA are bound to the enzyme, but that only the s-cis conformer is polarized. This selective polarization is an example of ground state strain, indicating the existence of catalytically relevant ground state destabilization arising from the selective complementarity of the enzyme toward the transition state rather than the ground state. Consequently, the stereoselectivity of the enzyme-catalyzed reaction results from the selective activation of one of two bound substrate conformers rather than from selective binding of a single conformer. These findings have important implications for inhibitor design and the role of ground state interactions in enzyme catalysis.
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Affiliation(s)
- Alasdair F Bell
- Department of Chemistry, Center for Structural Biology, SUNY at Stony Brook, Stony Brook, NY 11794, USA
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27
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Lillelund VH, Jensen HH, Liang X, Bols M. Recent developments of transition-state analogue glycosidase inhibitors of non-natural product origin. Chem Rev 2002; 102:515-53. [PMID: 11841253 DOI: 10.1021/cr000433k] [Citation(s) in RCA: 614] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Vinni H Lillelund
- Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
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28
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Hollis T, Lau A, Ellenberger T. Crystallizing thoughts about DNA base excision repair. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2002; 68:305-14. [PMID: 11554308 DOI: 10.1016/s0079-6603(01)68109-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Chemically damaged bases are removed from DNA by glycosylases that locate the damage and cleave the bond between the modified base and the deoxyribose sugar of the DNA backbone. The detection of damaged bases in DNA poses two problems: (1) The aberrant bases are mostly buried within the double helix, and (2) a wide variety of chemically different modifications must be efficiently recognized and removed. The human alkyladenine glycosylase (AAG) and Escherichia coli Alka DNA glycosylases excise many different types of alkylated bases from DNA. Crystal structures of these enzymes show how substrate bases are exposed to the enzyme active site and they suggest mechanisms of catalytic specificity. Both enzymes bend DNA and flip substrate bases out of the double helix and into the enzyme active site for cleavage. Although AAG and AlkA have very different overall folds, some common features of their substrate-binding sites suggest related strategies for the selective recognition of a chemically diverse group of alkylated substrates.
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Affiliation(s)
- T Hollis
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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29
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Abstract
Experimental analysis of enzymatic transition states by kinetic isotope effect methods has established geometric variation in related transition state structures. Differences are apparent in development of the reaction coordinate, in solvolytic transition states relative to those in enzymatic catalytic sites, in the stereochemistry of related substrates at the transition state, and in reactions catalyzed by related enzymes.
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Affiliation(s)
- V L Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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30
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Versées W, Decanniere K, Pellé R, Depoorter J, Brosens E, Parkin DW, Steyaert J. Structure and function of a novel purine specific nucleoside hydrolase from Trypanosoma vivax. J Mol Biol 2001; 307:1363-79. [PMID: 11292348 DOI: 10.1006/jmbi.2001.4548] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purine salvage pathway of parasitic protozoa is currently considered as a target for drug development because these organisms cannot synthesize purines de novo. Insight into the structure and mechanism of the involved enzymes can aid in the development of potent inhibitors, leading to new curative drugs. Nucleoside hydrolases are key enzymes in the purine salvage pathway of Trypanosomatidae, and they are especially attractive because they have no equivalent in mammalian cells. We cloned, expressed and purified a nucleoside hydrolase from Trypanosoma vivax. The substrate activity profile establishes the enzyme to be a member of the inosine-adenosine-guanosine-preferring nucleoside hydrolases (IAG-NH). We solved the crystal structure of the enzyme at 1.6 A resolution using MAD techniques. The complex of the enzyme with the substrate analogue 3-deaza-adenosine is presented. These are the first structures of an IAG-NH reported in the literature. The T. vivax IAG-NH is a homodimer, with each subunit consisting of ten beta-strands, 12 alpha-helices and three small 3(10)-helices. Six of the eight strands of the central beta-sheet form a motif resembling the Rossmann fold. Superposition of the active sites of this IAG-NH and the inosine-uridine-preferring nucleoside hydrolase (IU-NH) of Crithidia fasciculata shows the molecular basis of the different substrate specificity distinguishing these two classes of nucleoside hydrolases. An "aromatic stacking network" in the active site of the IAG-NH, absent from the IU-NH, imposes the purine specificity. Asp10 is the proposed general base in the reaction mechanism, abstracting a proton from a nucleophilic water molecule. Asp40 (replaced by Asn39 in the IU-NH) is positioned appropriately to act as a general acid and to protonate the purine leaving group. The second general acid, needed for full enzymatic activity, is probably part of a flexible loop located in the vicinity of the active site.
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Affiliation(s)
- W Versées
- Dienst Ultrastructuur, Vlaams Interuniversitair instituut voor Biotechnologie, Vrije Universiteit Brussel, Paardenstraat 65, Sint-Genesius-Rode, B-1640, Belgium
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31
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Enzymes. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50012-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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32
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Metzler DE, Metzler CM, Sauke DJ. Transferring Groups by Displacement Reactions. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50015-5] [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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33
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Rösler A, Panayotou G, Hornby DP, Barlow T, Brown T, Pearl LH, Savva R, Blackburn GM. The mechanism of DNA repair by uracil-DNA glycosylase: studies using nucleotide analogues. NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS 2000; 19:1505-16. [PMID: 11200255 DOI: 10.1080/15257770008045442] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
2',4'-Dideoxy-4'-methyleneuridine incorporated into oligodeoxynucleotides forms regular B-DNA duplexes as shown by Tm and CD measurements. Such oligomers are not cleaved by the DNA repair enzyme, UDG, which cleaves the glycosylic bond in dU but not in dT nor in dC nucleosides in single stranded and double stranded DNA. Differential binding of oligomers containing carbadU, 4'-thiodU, and dU residues to wild type and mutant UDG proteins identify an essential role for the furanose 4'-oxygen in recognition and cleavage of dU residues in DNA.
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Affiliation(s)
- A Rösler
- Krebs Institute, Department of Chemistry, Sheffield University, UK
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34
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Hollis T, Lau A, Ellenberger T. Structural studies of human alkyladenine glycosylase and E. coli 3-methyladenine glycosylase. Mutat Res 2000; 460:201-10. [PMID: 10946229 DOI: 10.1016/s0921-8777(00)00027-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Human alkyladenine glycosylase (AAG) and Escherichia coli 3-methyladenine glycosylase (AlkA) are base excision repair glycosylases that recognize and excise a variety of alkylated bases from DNA. The crystal structures of these enzymes have provided insight into their substrate specificity and mechanisms of catalysis. Both enzymes utilize DNA bending and base-flipping mechanisms to expose and bind substrate bases. Crystal structures of AAG complexed to DNA suggest that the enzyme selects substrate bases through a combination of hydrogen bonding and the steric constraints of the active site, and that the enzyme activates a water molecule for an in-line backside attack of the N-glycosylic bond. In contrast to AAG, the structure of the AlkA-DNA complex suggests that AlkA substrate recognition and catalytic specificity are intimately integrated in a S(N)1 type mechanism in which the catalytic Asp238 directly promotes the release of modified bases.
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Affiliation(s)
- T Hollis
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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35
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Le VD, Wong CH. Synthesis of 2-substituted polyhydroxytetrahydropyrimidines (N-hydroxy cyclic guanidino-sugars): transition-state mimics of enzymatic glycosidic cleavage. J Org Chem 2000; 65:2399-409. [PMID: 10789452 DOI: 10.1021/jo9915574] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis of 2'-substituted polyhydroxytetrahydropyrimidines as transition-state mimics of enzymatic glycosidic cleavage has been achieved by using guanylation and cyclization methodologies. The D-galacto type N-hydroxy cyclic guanidino-sugar 21 was synthesized in six steps from amine 7 and thiourea 14 in an overall yield of 59%. To further derivatize compound 21 to incorporate the leaving group moiety, we have synthesized 2-methylsulfanyl compounds 26-29 as key intermediates. The 2-methylsulfanyl group in 29 was displaced with amines, assisted by silver tetrafluoroborate as Lewis acid, to give protected cyclic guanidines 30-32 in moderate yields (60-67%). Removal of the protecting groups in 32 gave the D-galacto-type N-hydroxy cyclic guanidino-sugar 34. The key steps in the synthesis of the 6-deoxy-DL-galacto type N-hydroxy cyclic guanidino-sugars 49, 54, and 64-66 involve cyclization of the appropriate acetal intermediates (45, 50, and 58-60) followed by removal of the protecting groups.
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Affiliation(s)
- V D Le
- Department of Chemistry, Scripps Research Institute, La Jolla, California 92037, USA
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36
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Hehre EJ. A fresh understanding of the stereochemical behavior of glycosylases: structural distinction of "inverting" (2-MCO-type) versus "retaining" (1-MCO-type) enzymes. Adv Carbohydr Chem Biochem 2000; 55:265-310. [PMID: 10715782 DOI: 10.1016/s0065-2318(00)55007-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- E J Hehre
- Department of Microbiology and Immmunology, Albert Einstein College of Medicine, New York, USA
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37
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Abstract
Time and costs associated with the discovery of new drugs have been significantly reduced by enzyme structure-based approaches to the discovery of new chemotherapeutic agents. However, fundamental components of the overall approach continue to rely on technologies which, by their nature, involve relatively random processes (i.e., combinatorial chemistry and high-throughput screening). Thus, the efficiency of the drug discovery process potentially could be further improved through better use of structural information. In this regard, three-dimensional structures of enzymes are now being solved at high resolution and/or in conformations that provide data that should be more useful for inhibitor design or discovery. Scientists are beginning to appreciate the importance of water as a possible competitor of inhibitors for binding to target enzymes. New computational algorithms are improving the efficiency of identifying flexible inhibitors from among the large numbers of compounds in chemical databases. Also, tools of molecular genetics together with structures of target enzymes are likely to be used more frequently in dealing with the development of resistance to novel chemotherapeutic agents. Instead of detailing success stories in structure-based drug discovery, the following article considers how future efforts to discover or design new drugs may increasingly rely on information about molecular targets and less on data acquired via approaches involving random methodologies.
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Affiliation(s)
- S P Craig
- Laboratory of Molecular Parasitology & Drug Design, University of North Carolina School of Pharmacy, Chapel Hill 27599-7360, USA
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38
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Hollis T, Ichikawa Y, Ellenberger T. DNA bending and a flip-out mechanism for base excision by the helix-hairpin-helix DNA glycosylase, Escherichia coli AlkA. EMBO J 2000; 19:758-66. [PMID: 10675345 PMCID: PMC305614 DOI: 10.1093/emboj/19.4.758] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Escherichia coli AlkA protein is a base excision repair glycosylase that removes a variety of alkylated bases from DNA. The 2.5 A crystal structure of AlkA complexed to DNA shows a large distortion in the bound DNA. The enzyme flips a 1-azaribose abasic nucleotide out of DNA and induces a 66 degrees bend in the DNA with a marked widening of the minor groove. The position of the 1-azaribose in the enzyme active site suggests an S(N)1-type mechanism for the glycosylase reaction, in which the essential catalytic Asp238 provides direct assistance for base removal. Catalytic selectivity might result from the enhanced stacking of positively charged, alkylated bases against the aromatic side chain of Trp272 in conjunction with the relative ease of cleaving the weakened glycosylic bond of these modified nucleotides. The structure of the AlkA-DNA complex offers the first glimpse of a helix-hairpin-helix (HhH) glycosylase complexed to DNA. Modeling studies suggest that other HhH glycosylases can bind to DNA in a similar manner.
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Affiliation(s)
- T Hollis
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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39
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Jongejan A, Machado SS, Jongejan JA. The enantioselectivity of quinohaemoprotein alcohol dehydrogenases: mechanistic and structural aspects. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s1381-1177(99)00063-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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40
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Kline PC, Rezaee M, Lee TA. Determination of kinetic isotope effects for nucleoside hydrolases using gas chromatography/mass spectrometry. Anal Biochem 1999; 275:6-10. [PMID: 10542103 DOI: 10.1006/abio.1999.4308] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kinetic isotope effects are widely used to determine the transition state of chemical and enzymatic reactions. Radioactive isotopes are used most often to determine these kinetic isotope effects. However, stable isotopes offer a number of advantages over the use of radioactive isotopes. These advantages include ease of handling and disposal along with increased safety in the laboratory. [1'-(13)C]Inosine and [1'-(2)H]inosine kinetic isotope effects were determined using a gas chromatograph in conjunction with a mass selective detector for nucleoside hydrolase, a purine-metabolizing enzyme. Three ion pairs were used to determine kinetic isotope effects. These ion pairs were 158/159, 187/188, and 217/218. The average isotope effects for all ion pairs were 1.021 +/- 0.006 for [1'-(13)C]inosine and 1.113 +/- 0.008 for [1'-(2)H]inosine. The transition state consistent with these isotope effects is also consistent with the transition state proposed by Schramm and Horenstein using radioactive substrates.
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Affiliation(s)
- P C Kline
- Department of Chemistry, Middle Tennessee State University, Murfreesboro, Tennessee 37132, USA
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41
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Varaprasad CV, Averett D, Ramasamy KS, Wu J. Synthesis and structural studies of monocyclic 4′-Aza-L-Nucleosides. Tetrahedron 1999. [DOI: 10.1016/s0040-4020(99)00837-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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42
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Radominska-Pandya A, Czernik PJ, Little JM, Battaglia E, Mackenzie PI. Structural and functional studies of UDP-glucuronosyltransferases. Drug Metab Rev 1999; 31:817-99. [PMID: 10575553 DOI: 10.1081/dmr-100101944] [Citation(s) in RCA: 360] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
UDP-Glucuronosyltransferases (UGTs) are glycoproteins localized in the endoplasmic reticulum (ER) which catalyze the conjugation of a broad variety of lipophilic aglycon substrates with glucuronic acid using UDP-glucuronic acid (UDP-GIcUA) as the sugar donor. Glucuronidation is a major factor in the elimination of lipophilic compounds from the body. In this review, current information on the substrate specificities of UGT1A and 2B family isoforms is discussed. Recent findings with regard to UGT structure and topology are presented, including a dynamic topological model of UGTs in the ER. Evidence from experiments on UGT interactions with inhibitors directed at specific amino acids, photoaffinity labeling, and analysis of amino acid alignments suggest that UDP-GIcUA interacts with residues in both the N- and C-terminal domains, whereas aglycon binding sites are localized in the N-terminal domain. The amino acids identified so far as crucial for substrate binding and catalysis are arginine, lysine, histidine, proline, and residues containing carboxylic acid. Site-directed mutagenesis experiments are critical for unambiguous identification of the active-site architecture.
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Affiliation(s)
- A Radominska-Pandya
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock 72205, USA.
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43
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Affiliation(s)
- V L Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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44
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Tantillo DJ, Houk KN. Fidelity in Hapten Design: How Analogous Are Phosphonate Haptens to the Transition States for Alkaline Hydrolyses of Aryl Esters? J Org Chem 1999; 64:3066-3076. [PMID: 11674403 DOI: 10.1021/jo982335t] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Is antibody catalysis of hydrolysis reactions limited by imperfect mimicry of transition states by haptenic analogs? This question was explored by comparison of calculated transition states for the hydrolyses of aryl esters and the haptens intended to mimic them. The addition-elimination reaction of phenyl acetate and hydroxide ion in the gas phase was examined using ab initio calculations at the RHF/6-31+G(d)//RHF/6-31+G(d) and MP2/6-31+G(d)//RHF/6-31+G(d) levels of theory. Although transition states for both addition and elimination were located, the barrier to elimination disappeared when zero point energy or electron correlation was included. The reaction is therefore concerted, and the transition state for addition is the only relevant transition state in the gas phase. When aqueous solvation is considered through PCM and SCI-PCM calculations, the barrier to addition is shown to increase dramatically, and a stepwise addition-elimination pathway is predicted. A single transition state for the analogous reaction with p-nitrophenyl acetate was also located, and this reaction is predicted to be concerted in both the gas phase and in solution. The calculated geometries, CHELPG atomic charges, and electrostatic potential surfaces of stationary points involved in hydrolysis were compared with those of model phosphonate and phosphinate haptens. The haptens are better mimics of the two transition states and the tetrahedral intermediate than of the reactants or products-exactly the situation desired for catalyst generation-yet they are more analogous to the tetrahedral intermediate and the transition state for elimination than to the rate-determining addition transition state. In addition, the hydrogen-bonding pattern and asymmetry of the stationary points are not faithfully reproduced by the haptens. These considerations suggest that catalysis may be improved by hapten redesign or antibody mutagenesis.
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Affiliation(s)
- Dean J. Tantillo
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569
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45
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Xiao G, Tordova M, Jagadeesh J, Drohat AC, Stivers JT, Gilliland GL. Crystal structure ofEscherichia coli uracil DNA glycosylase and its complexes with uracil and glycerol: Structure and glycosylase mechanism revisited. Proteins 1999. [DOI: 10.1002/(sici)1097-0134(19990401)35:1<13::aid-prot2>3.0.co;2-2] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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46
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Sheikhnejad G, Brank A, Christman JK, Goddard A, Alvarez E, Ford H, Marquez VE, Marasco CJ, Sufrin JR, O'gara M, Cheng X. Mechanism of inhibition of DNA (cytosine C5)-methyltransferases by oligodeoxyribonucleotides containing 5,6-dihydro-5-azacytosine. J Mol Biol 1999; 285:2021-34. [PMID: 9925782 DOI: 10.1006/jmbi.1998.2426] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A key step in the predicted mechanism of enzymatic transfer of methyl groups from S-adenosyl-l-methionine (AdoMet) to cytosine residues in DNA is the transient formation of a dihydrocytosine intermediate covalently linked to cysteine in the active site of a DNA (cytosine C5)-methyltransferase (DNA C5-MTase). Crystallographic analysis of complexes formed by HhaI methyltransferase (M.HhaI), AdoMet and a target oligodeoxyribonucleotide containing 5-fluorocytosine confirmed the existence of this dihydrocytosine intermediate. Based on the premise that 5,6-dihydro-5-azacytosine (DZCyt), a cytosine analog with an sp3-hybridized carbon (CH2) at position 6 and an NH group at position 5, could mimic the non-aromatic character of the cytosine ring in this transition state, we synthesized a series of synthetic substrates for DNA C5-MTase containing DZCyt. Substitution of DZCyt for target cytosines in C-G dinucleotides of single-stranded or double-stranded oligodeoxyribonucleotide substrates led to complete inhibition of methylation by murine DNA C5-MTase. Substitution of DZCyt for the target cytosine in G-C-G-C sites in double-stranded oligodeoxyribonucleotides had a similar effect on methylation by M. HhaI. Oligodeoxyribonucleotides containing DZCyt formed a tight but reversible complex with M.HhaI, and were consistently more potent as inhibitors of DNA methylation than oligodeoxyribonucleotides identical in sequence containing 5-fluorocytosine. Crystallographic analysis of a ternary complex involving M.HhaI, S-adenosyl-l-homocysteine and a double-stranded 13-mer oligodeoxyribonucleotide containing DZCyt at the target position showed that the analog is flipped out of the DNA helix in the same manner as cytosine, 5-methylcytosine, and 5-fluorocytosine. However, no formation of a covalent bond was detected between the sulfur atom of the catalytic site nucleophile, cysteine 81, and the pyrimidine C6 carbon. These results indicate that DZCyt can occupy the active site of M.HhaI as a transition state mimic and, because of the high degree of affinity of its interaction with the enzyme, it can act as a potent inhibitor of methylation.
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Affiliation(s)
- G Sheikhnejad
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha 68198-4525, USA
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Lau AY, Schärer OD, Samson L, Verdine GL, Ellenberger T. Crystal structure of a human alkylbase-DNA repair enzyme complexed to DNA: mechanisms for nucleotide flipping and base excision. Cell 1998; 95:249-58. [PMID: 9790531 DOI: 10.1016/s0092-8674(00)81755-9] [Citation(s) in RCA: 225] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
DNA N-glycosylases are base excision-repair proteins that locate and cleave damaged bases from DNA as the first step in restoring the genetic blueprint. The human enzyme 3-methyladenine DNA glycosylase removes a diverse group of damaged bases from DNA, including cytotoxic and mutagenic alkylation adducts of purines. We report the crystal structure of human 3-methyladenine DNA glycosylase complexed to a mechanism-based pyrrolidine inhibitor. The enzyme has intercalated into the minor groove of DNA, causing the abasic pyrrolidine nucleotide to flip into the enzyme active site, where a bound water is poised for nucleophilic attack. The structure shows an elegant means of exposing a nucleotide for base excision as well as a network of residues that could catalyze the in-line displacement of a damaged base from the phosphodeoxyribose backbone.
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Affiliation(s)
- A Y Lau
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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Abstract
All chemical transformations pass through an unstable structure called the transition state, which is poised between the chemical structures of the substrates and products. The transition states for chemical reactions are proposed to have lifetimes near 10(-13) sec, the time for a single bond vibration. No physical or spectroscopic method is available to directly observe the structure of the transition state for enzymatic reactions. Yet transition state structure is central to understanding catalysis, because enzymes function by lowering activation energy. An accepted view of enzymatic catalysis is tight binding to the unstable transition state structure. Transition state mimics bind tightly to enzymes by capturing a fraction of the binding energy for the transition state species. The identification of numerous transition state inhibitors supports the transition state stabilization hypothesis for enzymatic catalysis. Advances in methods for measuring and interpreting kinetic isotope effects and advances in computational chemistry have provided an experimental route to understand transition state structure. Systematic analysis of intrinsic kinetic isotope effects provides geometric and electronic structure for enzyme-bound transition states. This information has been used to compare transition states for chemical and enzymatic reactions; determine whether enzymatic activators alter transition state structure; design transition state inhibitors; and provide the basis for predicting the affinity of enzymatic inhibitors. Enzymatic transition states provide an understanding of catalysis and permit the design of transition state inhibitors. This article reviews transition state theory for enzymatic reactions. Selected examples of enzymatic transition states are compared to the respective transition state inhibitors.
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Affiliation(s)
- V L Schramm
- Department of Biochemistry, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA.
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Chen XY, Link TM, Schramm VL. Ricin A-chain: kinetics, mechanism, and RNA stem-loop inhibitors. Biochemistry 1998; 37:11605-13. [PMID: 9708998 DOI: 10.1021/bi980990p] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Ricin A-chain (RTA) catalyzes the depurination of a single adenine at position 4324 of 28S rRNA in a N-ribohydrolase reaction. The mechanism and specificity for RTA are examined using RNA stem-loop structures of 10-18 nucleotides which contain the required substrate motif, a GAGA tetraloop. At the optimal pH near 4.0, the preferred substrate is a 14-base stem-loop RNA which is hydrolyzed at 219 min-1 with a kcat/Km of 4.5 x 10(5) M-1 s-1 under conditions of steady-state catalysis. Smaller or larger stem-loop RNAs have lower kcat values, but all have Km values of approximately 5 microM. Both the 10- and 18-base substrates have kcat/Km near 10(4) M-1 s-1. Covalent cross-linking of the stem has a small effect on the kinetic parameters. Stem-loop DNA (10 bases) of the same sequence is also a substrate with a kcat/Km of 0.1 that for RNA. Chemical mechanisms for enzymatic RNA depurination reactions include leaving group activation, stabilization of a ribooxocarbenium transition state, a covalent enzyme-ribosyl intermediate, and ionization of the 2'-hydroxyl. A stem-loop RNA with p-nitrophenyl O-riboside at the depurination site is not a substrate, but binds tightly to the enzyme (Ki = 0.34 microM), consistent with a catalytic mechanism of leaving group activation. The substrate activity of stem-loop DNA eliminates ionization of the 2'-hydroxyl as a mechanism. Incorporation of the C-riboside formycin A at the depurination site provides an increased pKa of the adenine analogue at N7. Binding of this analogue (Ki = 9.4 microM) is weaker than substrate which indicates that the altered pKa at this position is not an important feature of transition state recognition. Stem-loop RNA with phenyliminoribitol at the depurination site increases the affinity substantially (Ki = 0.18 microM). The results are consistent with catalysis occurring by leaving group protonation at ring position(s) other than N7 leading to a ribooxocarbenium ion transition state. Small stem-loop RNAs have been identified with substrate activity within an order of magnitude of that reported for intact ribosomes.
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Affiliation(s)
- X Y Chen
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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