1
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Taylor AE, Mellbye BL. Differential Responses of the Catalytic Efficiency of Ammonia and Nitrite Oxidation to Changes in Temperature. Front Microbiol 2022; 13:817986. [PMID: 35620102 PMCID: PMC9127996 DOI: 10.3389/fmicb.2022.817986] [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: 11/18/2021] [Accepted: 04/08/2022] [Indexed: 11/13/2022] Open
Abstract
Microbially mediated nitrification plays an important role in the nitrogen (N) cycle, and rates of activity have been shown to change significantly with temperature. Despite this, the substrate affinities of nitrifying bacteria and archaea have not been comprehensively measured and are often assumed to be static in mathematical models of environmental systems. In this study, we measured the oxidation kinetics of ammonia- (NH3) oxidizing archaea (AOA), NH3-oxidizing bacteria (AOB), and two distinct groups of nitrite (NO2 -)-oxidizing bacteria (NOB), of the genera Nitrobacter and Nitrospira, by measuring the maximum rates of apparent activity (V max(app)), the apparent half-saturation constant (K m(app)), and the overall catalytic efficiency (V max(app) /K m(app)) over a range of temperatures. Changes in V max(app) and K m(app) with temperature were different between groups, with V max(app) and catalytic efficiency increasing with temperature in AOA, while V max(app) , K m(app), and catalytic efficiency increased in AOB. In Nitrobacter NOB, V max(app) and K m(app) increased, but catalytic efficiency decreased significantly with temperature. Nitrospira NOB were variable, but V max(app) increased while catalytic efficiency and K m(app) remained relatively unchanged. Michaelis-Menten (MM) and Haldane (H) kinetic models of NH3 oxidation and NO2 - oxidation based on the collected data correctly predict nitrification potential in some soil incubation experiments, but not others. Despite previous observations of coupled nitrification in many natural systems, our results demonstrate significant differences in response to temperature strategies between the different groups of nitrifiers; and indicate the need to further investigate the response of nitrifiers to environmental changes.
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Affiliation(s)
- Anne E. Taylor
- Department of Crop and Soil Science, Oregon State University, Corvallis, OR, United States
| | - Brett L. Mellbye
- Department of Microbiology, Oregon State University, Corvallis, OR, United States
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2
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Starch as the Flame Retardant for Electrolytes in Lithium-Ion Cells. MATERIALS 2022; 15:ma15020523. [PMID: 35057241 PMCID: PMC8780195 DOI: 10.3390/ma15020523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/03/2022] [Accepted: 01/06/2022] [Indexed: 11/17/2022]
Abstract
The main purpose of this work is to illustrate the flame retardant properties of corn starch that is used as an additive to the classic electrolytes in lithium-ion cells. The advantages of using natural biomass include the increased biodegradability of the cell, compliance with the slogan of green chemistry, as well as the widespread availability and easy isolation of this ingredient. Due to the non-Newtonian properties of starch, it increases work safety and prevents the occurrence of thermal runaway as a shear-thinning fluid in the event of a collision. Thus, its use may, in the future, prevent explosions that affect electric cars with lithium-ion batteries without significantly degrading the electrochemical parameters of the cell. In the manuscript, the viscosity test, flash point measurements, the SET (self-extinguishing time) test and conductivity measurements were performed, in addition to the determination of electrochemical impedance spectroscopy (EIS) for the anode system. Additionally, the kinetic and thermodynamic parameters, for both flow and conductivity, were determined for a deeper analysis; this constitutes the scientific novelty of this study. Through mathematical analysis, it was shown that the optimal amount of added starch is 5%. This is supported primarily by the determined kinetic and thermodynamic parameters and the fact that the system did not gel during heating.
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3
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Quirke JCK, Crich D. Side Chain Conformation Restriction in the Catalysis of Glycosidic Bond Formation by Leloir Glycosyltransferases, Glycoside Phosphorylases, and Transglycosidases. ACS Catal 2021; 11:5069-5078. [PMID: 34367723 PMCID: PMC8336929 DOI: 10.1021/acscatal.1c00896] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Carbohydrate side chain conformation is an important factor in the control of reactivity at the anomeric center, ie, in the making and breaking of glycosidic bonds, whether chemically or, for hydrolysis, by glycoside hydrolases. In nature glycosidic bond formation is catalyzed out by glycosyltransferases (GTs), glycoside phosphoryases, and transglycosidases. By analysis of 118 crystal structures of sugar nucleotide dependent (Leloir) GTs, 136 crystal structures of glycoside phosphorylases, and 54 crystal structures of transglycosidases bound to hexopyranosides or their analogs at the donor site (-1 site), we determined that most enzymes that catalyze glycoside synthesis, be they GTs, glycoside phosphorylases or transglycosidases, restrict their substrate side chains to the most reactive gauche,gauche (gg) conformation to achieve maximum stabilization of the oxocarbenium ion-like transition state for glycosyl transfer. The galactose series deviates from this trend, with α-galactosyltransferases preferentially restricting their substrates to the second-most reactive gauche,trans (gt) conformation, and β-galactosyltransferases favoring the least reactive trans,gauche (tg) conformation. This insight will help progress the design and development of improved, conformationally-restricted GT inhibitors that take advantage of these inherent side chain preferences.
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Affiliation(s)
- Jonathan C. K. Quirke
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 250 West Green Street, Athens, GA 30602, USA
- Department of Chemistry, University of Georgia, 140 Cedar Street, Athens, GA 30602, USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
| | - David Crich
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 250 West Green Street, Athens, GA 30602, USA
- Department of Chemistry, University of Georgia, 140 Cedar Street, Athens, GA 30602, USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
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4
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Vaccine design through transition state mimicry of heroin hydrolysis. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.153045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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De Tarafder A, Parajuli NP, Majumdar S, Kaçar B, Sanyal S. Kinetic Analysis Suggests Evolution of Ribosome Specificity in Modern Elongation Factor-Tus from "Generalist" Ancestors. Mol Biol Evol 2021; 38:3436-3444. [PMID: 33871630 PMCID: PMC8321524 DOI: 10.1093/molbev/msab114] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
It has been hypothesized that early enzymes are more promiscuous than their extant orthologs. Whether or not this hypothesis applies to the translation machinery, the oldest molecular machine of life, is not known. Efficient protein synthesis relies on a cascade of specific interactions between the ribosome and the translation factors. Here, using elongation factor-Tu (EF-Tu) as a model system, we have explored the evolution of ribosome specificity in translation factors. Employing presteady state fast kinetics using quench flow, we have quantitatively characterized the specificity of two sequence-reconstructed 1.3- to 3.3-Gy-old ancestral EF-Tus toward two unrelated bacterial ribosomes, mesophilic Escherichia coli and thermophilic Thermus thermophilus. Although the modern EF-Tus show clear preference for their respective ribosomes, the ancestral EF-Tus show similar specificity for diverse ribosomes. In addition, despite increase in the catalytic activity with temperature, the ribosome specificity of the thermophilic EF-Tus remains virtually unchanged. Our kinetic analysis thus suggests that EF-Tu proteins likely evolved from the catalytically promiscuous, “generalist” ancestors. Furthermore, compatibility of diverse ribosomes with the modern and ancestral EF-Tus suggests that the ribosomal core probably evolved before the diversification of the EF-Tus. This study thus provides important insights regarding the evolution of modern translation machinery.
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Affiliation(s)
- Arindam De Tarafder
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | | | - Soneya Majumdar
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Betül Kaçar
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA.,Lunar and Planetary Laboratory and Steward Observatory University of Arizona, Tucson, AZ, USA
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
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6
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Schneider NO, Tassoulas LJ, Zeng D, Laseke AJ, Reiter NJ, Wackett LP, Maurice MS. Solving the Conundrum: Widespread Proteins Annotated for Urea Metabolism in Bacteria Are Carboxyguanidine Deiminases Mediating Nitrogen Assimilation from Guanidine. Biochemistry 2020; 59:3258-3270. [PMID: 32786413 DOI: 10.1021/acs.biochem.0c00537] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Free guanidine is increasingly recognized as a relevant molecule in biological systems. Recently, it was reported that urea carboxylase acts preferentially on guanidine, and consequently, it was considered to participate directly in guanidine biodegradation. Urea carboxylase combines with allophanate hydrolase to comprise the activity of urea amidolyase, an enzyme predominantly found in bacteria and fungi that catalyzes the carboxylation and subsequent hydrolysis of urea to ammonia and carbon dioxide. Here, we demonstrate that urea carboxylase and allophanate hydrolase from Pseudomonas syringae are insufficient to catalyze the decomposition of guanidine. Rather, guanidine is decomposed to ammonia through the combined activities of urea carboxylase, allophanate hydrolase, and two additional proteins of the DUF1989 protein family, expansively annotated as urea carboxylase-associated family proteins. These proteins comprise the subunits of a heterodimeric carboxyguanidine deiminase (CgdAB), which hydrolyzes carboxyguanidine to N-carboxyurea (allophanate). The genes encoding CgdAB colocalize with genes encoding urea carboxylase and allophanate hydrolase. However, 25% of urea carboxylase genes, including all fungal urea amidolyases, do not colocalize with cgdAB. This subset of urea carboxylases correlates with a notable Asp to Asn mutation in the carboxyltransferase active site. Consistent with this observation, we demonstrate that fungal urea amidolyase retains a strong substrate preference for urea. The combined activities of urea carboxylase, carboxyguanidine deiminase and allophanate hydrolase represent a newly recognized pathway for the biodegradation of guanidine. These findings reinforce the relevance of guanidine as a biological metabolite and reveal a broadly distributed group of enzymes that act on guanidine in bacteria.
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Affiliation(s)
- Nicholas O Schneider
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Lambros J Tassoulas
- BioTechnology Institute, University of Minnesota, St. Paul, Minnesota 55108-6106, United States.,Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota 55108-6106, United States
| | - Danyun Zeng
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Amanda J Laseke
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Nicholas J Reiter
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Lawrence P Wackett
- BioTechnology Institute, University of Minnesota, St. Paul, Minnesota 55108-6106, United States.,Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota 55108-6106, United States
| | - Martin St Maurice
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
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7
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Xie L, Yang M, Chen ZN. Understanding the entropic effect in chorismate mutase reaction catalyzed by isochorismate-pyruvate lyase fromPseudomonas aeruginosa(PchB). Catal Sci Technol 2019. [DOI: 10.1039/c8cy02123f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The substrate preorganization process in the entropically driven PchB-catalyzed chorismate mutase reaction leads to a remarkable apparent entropic effect.
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Affiliation(s)
- Liangxu Xie
- State Key Laboratory of Structural Chemistry
- Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences
- Fuzhou 350002
- China
- Department of Chemistry
| | - Mingjun Yang
- XtalPi Inc. (Shenzhen Jingtai Technology Co., Ltd.)
- Times Science & Tech Mansion E. 20F
- Shenzhen
- China
| | - Zhe-Ning Chen
- State Key Laboratory of Structural Chemistry
- Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences
- Fuzhou 350002
- China
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8
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Kulkarni Y, Kamerlin SCL. Computational physical organic chemistry using the empirical valence bond approach. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2019. [DOI: 10.1016/bs.apoc.2019.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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9
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10
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In Vivo Titration of Folate Pathway Enzymes. Appl Environ Microbiol 2018; 84:AEM.01139-18. [PMID: 30030232 DOI: 10.1128/aem.01139-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 07/18/2018] [Indexed: 12/12/2022] Open
Abstract
How enzymes behave in cells is likely different from how they behave in the test tube. Previous in vitro studies find that osmolytes interact weakly with folate. Removal of the osmolyte from the solvation shell of folate is more difficult than removal of water, which weakens binding of folate to its enzyme partners. To examine if this phenomenon occurs in vivo, osmotic stress titrations were performed with Escherichia coli Two strategies were employed: resistance to an antibacterial drug and complementation of a knockout strain by the appropriate gene cloned into a plasmid that allows tight control of expression levels as well as labeling by a degradation tag. The abilities of the knockout and complemented strains to grow under osmotic stress were compared. Typically, the knockout strain could grow to high osmolalities on supplemented medium, while the complemented strain stopped growing at lower osmolalities on minimal medium. This pattern was observed for an R67 dihydrofolate reductase clone rescuing a ΔfolA strain, for a methylenetetrahydrofolate reductase clone rescuing a ΔmetF strain, and for a serine hydroxymethyltransferase clone rescuing a ΔglyA strain. Additionally, an R67 dihydrofolate reductase clone allowed E. coli DH5α to grow in the presence of trimethoprim until an osmolality of ∼0.81 is reached, while cells in a control titration lacking antibiotic could grow to 1.90 osmol.IMPORTANCEE. coli can survive in drought and flooding conditions and can tolerate large changes in osmolality. However, the cell processes that limit bacterial growth under high osmotic stress conditions are not known. In this study, the dose of four different enzymes in E. coli was decreased by using deletion strains complemented by the gene carried in a tunable plasmid. Under conditions of limiting enzyme concentration (lower than that achieved by chromosomal gene expression), cell growth can be blocked by osmotic stress conditions that are normally tolerated. These observations indicate that E. coli has evolved to deal with variations in its osmotic environment and that normal protein levels are sufficient to buffer the cell from environmental changes. Additional factors involved in the osmotic pressure response may include altered protein concentration/activity levels, weak solute interactions with ligands which can make it more difficult for proteins to bind their substrates/inhibitors/cofactors in vivo, and/or viscosity effects.
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11
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Allison SD, Romero-Olivares AL, Lu Y, Taylor JW, Treseder KK. Temperature sensitivities of extracellular enzyme V max and K m across thermal environments. GLOBAL CHANGE BIOLOGY 2018; 24:2884-2897. [PMID: 29322601 DOI: 10.1111/gcb.14045] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/14/2017] [Accepted: 12/20/2017] [Indexed: 05/12/2023]
Abstract
The magnitude and direction of carbon cycle feedbacks under climate warming remain uncertain due to insufficient knowledge about the temperature sensitivities of soil microbial processes. Enzymatic rates could increase at higher temperatures, but this response could change over time if soil microbes adapt to warming. We used the Arrhenius relationship, biochemical transition state theory, and thermal physiology theory to predict the responses of extracellular enzyme Vmax and Km to temperature. Based on these concepts, we hypothesized that Vmax and Km would correlate positively with each other and show positive temperature sensitivities. For enzymes from warmer environments, we expected to find lower Vmax , Km , and Km temperature sensitivity but higher Vmax temperature sensitivity. We tested these hypotheses with isolates of the filamentous fungus Neurospora discreta collected from around the globe and with decomposing leaf litter from a warming experiment in Alaskan boreal forest. For Neurospora extracellular enzymes, Vmax Q10 ranged from 1.48 to 2.25, and Km Q10 ranged from 0.71 to 2.80. In agreement with theory, Vmax and Km were positively correlated for some enzymes, and Vmax declined under experimental warming in Alaskan litter. However, the temperature sensitivities of Vmax and Km did not vary as expected with warming. We also found no relationship between temperature sensitivity of Vmax or Km and mean annual temperature of the isolation site for Neurospora strains. Declining Vmax in the Alaskan warming treatment implies a short-term negative feedback to climate change, but the Neurospora results suggest that climate-driven changes in plant inputs and soil properties are important controls on enzyme kinetics in the long term. Our empirical data on enzyme Vmax , Km , and temperature sensitivities should be useful for parameterizing existing biogeochemical models, but they reveal a need to develop new theory on thermal adaptation mechanisms.
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Affiliation(s)
- Steven D Allison
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
- Department of Earth System Science, University of California, Irvine, CA, USA
| | | | - Ying Lu
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
| | - John W Taylor
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Kathleen K Treseder
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA
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12
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13
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Abstract
The quantum chemical cluster approach is a powerful method for investigating enzymatic reactions. Over the past two decades, a large number of highly diverse systems have been studied and a great wealth of mechanistic insight has been developed using this technique. This Perspective reviews the current status of the methodology. The latest technical developments are highlighted, and challenges are discussed. Some recent applications are presented to illustrate the capabilities and progress of this approach, and likely future directions are outlined.
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Affiliation(s)
- Fahmi Himo
- Arrhenius Laboratory, Department of Organic Chemistry, Stockholm University , SE-106 91 Stockholm, Sweden
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14
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Abstract
The role played by entropy for the enormous rate enhancement achieved by enzymes has been debated for many decades. There are, for example, several confirmed cases where the activation free energy is reduced by around 10 kcal/mol due to entropic effects, corresponding to a rate enhancement of ∼107 compared to the uncatalyzed reaction. However, despite substantial efforts from both the experimental and theoretical side, no real consensus has been reached regarding the origin of such large entropic contributions to enzyme catalysis. Another remarkable instance of entropic effects is found in enzymes that are adapted by evolution to work at low temperatures, near the freezing point of water. These cold-adapted enzymes invariably show a more negative entropy and a lower enthalpy of activation than their mesophilic orthologs, which counteracts the exponential damping of reaction rates at lower temperature. The structural origin of this universal phenomenon has, however, remained elusive. The basic problem with connecting macroscopic thermodynamic quantities, such as activation entropy and enthalpy derived from Arrhenius plots, to the 3D protein structure is that the underlying detailed (microscopic) energetics is essentially inaccessible to experiment. Moreover, attempts to calculate entropy contributions by computer simulations have mostly focused only on substrate entropies, which do not provide the full picture. We have recently devised a new approach for accessing thermodynamic activation parameters of both enzyme and solution reactions from computer simulations, which turns out to be very successful. This method is analogous to the experimental Arrhenius plots and directly evaluates the temperature dependence of calculated reaction free energy profiles. Hence, by extensive molecular dynamics simulations and calculations of up to thousands of independent free energy profiles, we are able to extract activation parameters with sufficient precision for making direct comparisons to experiment. We show here that the agreement with the measured quantities, for both enzyme catalyzed and spontaneous solution reactions, is quite remarkable. Importantly, we can now address some of the most spectacular entropy effects in enzymes and clarify their detailed microscopic origin. Herein, we discuss as examples the conversion of cytidine to uridine catalyzed by cytidine deaminase and reactions taking place on the ribosome, namely, peptide bond formation and GTP hydrolysis by elongation factor Tu. It turns out that the large entropy contributions to catalysis in these cases can now be rationalized by our computational approach. Finally, we address the problem of cold adaptation of enzyme reaction rates and prove by computational experiments that the universal activation enthalpy-entropy phenomenon originates from mechanical properties of the outer protein surface.
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Affiliation(s)
- Johan Åqvist
- Department
of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Masoud Kazemi
- Department
of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Geir Villy Isaksen
- Department
of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
- The
Centre for Theoretical Computational Chemistry, Department of Chemistry, University of Tromsø, N9037 Tromsø, Norway
| | - Bjørn Olav Brandsdal
- The
Centre for Theoretical Computational Chemistry, Department of Chemistry, University of Tromsø, N9037 Tromsø, Norway
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15
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Balachandran N, To F, Berti PJ. Linear Free Energy Relationship Analysis of Transition State Mimicry by 3-Deoxy-d-arabino-heptulosonate-7-phosphate (DAHP) Oxime, a DAHP Synthase Inhibitor and Phosphate Mimic. Biochemistry 2017; 56:592-601. [PMID: 28045507 DOI: 10.1021/acs.biochem.6b01211] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Naresh Balachandran
- Department of Chemistry & Chemical Biology and ‡Department of Biochemistry & Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
| | - Frederick To
- Department of Chemistry & Chemical Biology and ‡Department of Biochemistry & Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
| | - Paul J. Berti
- Department of Chemistry & Chemical Biology and ‡Department of Biochemistry & Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
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16
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Cytosine deamination and the precipitous decline of spontaneous mutation during Earth's history. Proc Natl Acad Sci U S A 2016; 113:8194-9. [PMID: 27382162 DOI: 10.1073/pnas.1607580113] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hydrolytic deamination of cytosine and 5-methylcytosine residues in DNA appears to contribute significantly to the appearance of spontaneous mutations in microorganisms and in human disease. In the present work, we examined the mechanism of cytosine deamination and the response of the uncatalyzed reaction to changing temperature. The positively charged 1,3-dimethylcytosinium ion was hydrolyzed at a rate similar to the rate of acid-catalyzed hydrolysis of 1-methylcytosine, for which it furnishes a satisfactory kinetic model and a probable mechanism. In agreement with earlier reports, uncatalyzed deamination was found to proceed at very similar rates for cytosine, 1-methylcytosine, cytidine, and cytidine 5'-phosphate, and also for cytosine residues in single-stranded DNA generated from a phagemid, in which we sequenced an insert representing the gene of the HIV-1 protease. Arrhenius plots for the uncatalyzed deamination of cytosine were linear over the temperature range from 90 °C to 200 °C and indicated a heat of activation (ΔH(‡)) of 23.4 ± 0.5 kcal/mol at pH 7. Recent evidence indicates that the surface of the earth has been cool enough to support life for more than 4 billion years and that life has been present for almost as long. If the temperature at Earth's surface is assumed to have followed Newton's law of cooling, declining exponentially from 100 °C to 25 °C during that period, then half of the cytosine-deaminating events per unit biomass would have taken place during the first 0.2 billion years, and <99.4% would have occurred during the first 2 billion years.
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Affiliation(s)
- Adrian J Mulholland
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
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18
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Abstract
Entropic effects have often been invoked to explain the extraordinary catalytic power of enzymes. In particular, the hypothesis that enzymes can use part of the substrate-binding free energy to reduce the entropic penalty associated with the subsequent chemical transformation has been very influential. The enzymatic reaction of cytidine deaminase appears to be a distinct example. Here, substrate binding is associated with a significant entropy loss that closely matches the activation entropy penalty for the uncatalyzed reaction in water, whereas the activation entropy for the rate-limiting catalytic step in the enzyme is close to zero. Herein, we report extensive computer simulations of the cytidine deaminase reaction and its temperature dependence. The energetics of the catalytic reaction is first evaluated by density functional theory calculations. These results are then used to parametrize an empirical valence bond description of the reaction, which allows efficient sampling by molecular dynamics simulations and computation of Arrhenius plots. The thermodynamic activation parameters calculated by this approach are in excellent agreement with experimental data and indeed show an activation entropy close to zero for the rate-limiting transition state. However, the origin of this effect is a change of reaction mechanism compared the uncatalyzed reaction. The enzyme operates by hydroxide ion attack, which is intrinsically associated with a favorable activation entropy. Hence, this has little to do with utilization of binding free energy to pay the entropic penalty but rather reflects how a preorganized active site can stabilize a reaction path that is not operational in solution.
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Cacciapuoti G, Bagarolo ML, Martino E, Scafuri B, Marabotti A, Porcelli M. Efficient Fludarabine-Activating PNP From Archaea as a Guidance for Redesign the Active Site of E. Coli PNP. J Cell Biochem 2015; 117:1126-35. [PMID: 26477689 DOI: 10.1002/jcb.25396] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/06/2015] [Indexed: 11/08/2022]
Abstract
The combination of the gene of purine nucleoside phosphorylase (PNP) from Escherichia coli and fludarabine represents one of the most promising systems in the gene therapy of solid tumors. The use of fludarabine in gene therapy is limited by the lack of an enzyme that is able to efficiently activate this prodrug which, consequently, has to be administered in high doses that cause serious side effects. In an attempt to identify enzymes with a better catalytic efficiency than E. coli PNP towards fludarabine to be used as a guidance on how to improve the activity of the bacterial enzyme, we have selected 5'-deoxy-5'-methylthioadenosine phosphorylase (SsMTAP) and 5'-deoxy-5'-methylthioadenosine phosphorylase II (SsMTAPII), two PNPs isolated from the hyperthermophilic archaeon Sulfolobus solfataricus. Substrate specificity and catalytic efficiency of SsMTAP and SsMTAPII for fludarabine were analyzed by kinetic studies and compared with E. coli PNP. SsMTAP and SsMTAPII share with E. coli PNP a comparable low affinity for the arabinonucleoside but are better catalysts of fludarabine cleavage with k(cat)/K(m) values that are 12.8-fold and 6-fold higher, respectively, than those reported for the bacterial enzyme. A computational analysis of the interactions of fludarabine in the active sites of E. coli PNP, SsMTAP, and SsMTAPII allowed to identify the crucial residues involved in the binding with this substrate, and provided structural information to improve the catalytic efficiency of E. coli PNP by enzyme redesign.
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Affiliation(s)
- Giovanna Cacciapuoti
- Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Via L. De Crecchio 7, Naples, 80138, Italy
| | - Maria Libera Bagarolo
- Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Via L. De Crecchio 7, Naples, 80138, Italy
| | - Elisa Martino
- Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Via L. De Crecchio 7, Naples, 80138, Italy
| | - Bernardina Scafuri
- Department of Chemistry and Biology, University of Salerno, Via Giovanni Paolo II 132, Fisciano, Salerno, 84084, Italy
| | - Anna Marabotti
- Department of Chemistry and Biology, University of Salerno, Via Giovanni Paolo II 132, Fisciano, Salerno, 84084, Italy
| | - Marina Porcelli
- Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Via L. De Crecchio 7, Naples, 80138, Italy
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20
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Kazemi M, Åqvist J. Chemical reaction mechanisms in solution from brute force computational Arrhenius plots. Nat Commun 2015; 6:7293. [PMID: 26028237 PMCID: PMC4458863 DOI: 10.1038/ncomms8293] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/24/2015] [Indexed: 12/23/2022] Open
Abstract
Decomposition of activation free energies of chemical reactions, into enthalpic and entropic components, can provide invaluable signatures of mechanistic pathways both in solution and in enzymes. Owing to the large number of degrees of freedom involved in such condensed-phase reactions, the extensive configurational sampling needed for reliable entropy estimates is still beyond the scope of quantum chemical calculations. Here we show, for the hydrolytic deamination of cytidine and dihydrocytidine in water, how direct computer simulations of the temperature dependence of free energy profiles can be used to extract very accurate thermodynamic activation parameters. The simulations are based on empirical valence bond models, and we demonstrate that the energetics obtained is insensitive to whether these are calibrated by quantum mechanical calculations or experimental data. The thermodynamic activation parameters are in remarkable agreement with experiment results and allow discrimination among alternative mechanisms, as well as rationalization of their different activation enthalpies and entropies. Obtaining activation entropies and enthalpies of a reaction is important for distinguishing between alternative reaction mechanisms. Here the authors use computational methods to accurately obtain the enthalpic/entropic components of the activation free energy for hydrolytic deamination reactions.
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Affiliation(s)
- Masoud Kazemi
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Johan Åqvist
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
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21
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Bains W, Xiao Y, Yu C. Prediction of the maximum temperature for life based on the stability of metabolites to decomposition in water. Life (Basel) 2015; 5:1054-100. [PMID: 25821932 PMCID: PMC4500130 DOI: 10.3390/life5021054] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/03/2015] [Accepted: 03/05/2015] [Indexed: 12/01/2022] Open
Abstract
The components of life must survive in a cell long enough to perform their function in that cell. Because the rate of attack by water increases with temperature, we can, in principle, predict a maximum temperature above which an active terrestrial metabolism cannot function by analysis of the decomposition rates of the components of life, and comparison of those rates with the metabolites' minimum metabolic half-lives. The present study is a first step in this direction, providing an analytical framework and method, and analyzing the stability of 63 small molecule metabolites based on literature data. Assuming that attack by water follows a first order rate equation, we extracted decomposition rate constants from literature data and estimated their statistical reliability. The resulting rate equations were then used to give a measure of confidence in the half-life of the metabolite concerned at different temperatures. There is little reliable data on metabolite decomposition or hydrolysis rates in the literature, the data is mostly confined to a small number of classes of chemicals, and the data available are sometimes mutually contradictory because of varying reaction conditions. However, a preliminary analysis suggests that terrestrial biochemistry is limited to environments below ~150-180 °C. We comment briefly on why pressure is likely to have a small effect on this.
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Affiliation(s)
- William Bains
- Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Mass. Avenue, Cambridge, MA 02139, USA.
| | - Yao Xiao
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QT, UK.
| | - Changyong Yu
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QT, UK.
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22
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Sánchez-Quitian ZA, Rodrigues-Junior V, Rehm JG, Eichler P, Barbosa Trivella DB, Bizarro CV, Basso LA, Santos DS. Functional and structural evidence for the catalytic role played by glutamate-47 residue in the mode of action of Mycobacterium tuberculosis cytidine deaminase. RSC Adv 2015. [DOI: 10.1039/c4ra13748e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Glutamate-47 plays a catalytic role in the mode of action ofMycobacterium tuberculosiscytidine deaminase.
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Affiliation(s)
- Zilpa Adriana Sánchez-Quitian
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
| | - Valnês Rodrigues-Junior
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
| | - Jacqueline Gonçalves Rehm
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
| | - Paula Eichler
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
| | | | - Cristiano Valim Bizarro
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
| | - Luiz Augusto Basso
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
| | - Diogenes Santiago Santos
- Centro de Pesquisas em Biologia Molecular e Funcional (CPBMF)
- Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB)
- Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS)
- Porto Alegre
- Brazil
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23
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Wolfenden R. Massive thermal acceleration of the emergence of primordial chemistry, the incidence of spontaneous mutation, and the evolution of enzymes. J Biol Chem 2014; 289:30198-30204. [PMID: 25210030 DOI: 10.1074/jbc.r114.567081] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Kelvin considered it unlikely that sufficient time had elapsed on the earth for life to have reached its present level of complexity. In the warm surroundings in which life first appeared, however, elevated temperatures would have reduced the kinetic barriers to reaction. Recent experiments disclose the profound extent to which very slow reactions are accelerated by elevated temperatures, collapsing the time that would have been required for early events in primordial chemistry before the advent of enzymes. If a primitive enzyme, like model catalysts and most modern enzymes, accelerated a reaction by lowering its enthalpy of activation, then the rate enhancement that it produced would have increased automatically as the environment cooled, quite apart from any improvements in catalytic activity that arose from mutation and natural selection. The chemical events responsible for spontaneous mutation are also highly sensitive to temperature, furnishing an independent mechanism for accelerating evolution.
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Affiliation(s)
- Richard Wolfenden
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260.
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24
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Mak WS, Siegel JB. Computational enzyme design: Transitioning from catalytic proteins to enzymes. Curr Opin Struct Biol 2014; 27:87-94. [DOI: 10.1016/j.sbi.2014.05.010] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Revised: 05/23/2014] [Accepted: 05/30/2014] [Indexed: 12/14/2022]
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25
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Graham JD, Buytendyk AM, Wang D, Bowen KH, Collins KD. Strong, low-barrier hydrogen bonds may be available to enzymes. Biochemistry 2014; 53:344-9. [PMID: 24359447 DOI: 10.1021/bi4014566] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The debate over the possible role of strong, low-barrier hydrogen bonds in stabilizing reaction intermediates at enzyme active sites has taken place in the absence of an awareness of the upper limits to the strengths of low-barrier hydrogen bonds involving amino acid side chains. Hydrogen bonds exhibit their maximal strengths in isolation, i.e., in the gas phase. In this work, we measured the ionic hydrogen bond strengths of three enzymatically relevant model systems in the gas phase using anion photoelectron spectroscopy; we calibrated these against the hydrogen bond strength of HF2(-), measured using the same technique, and we compared our results with other gas-phase experimental data. The model systems studied here, the formate-formic acid, acetate-acetic acid, and imidazolide-imidazole anionic complexes, all exhibit very strong hydrogen bonds, whose strengths compare favorably with that of the hydrogen bifluoride anion, the strongest known hydrogen bond. The hydrogen bond strengths of these gas-phase complexes are stronger than those typically estimated as being required to stabilize enzymatic intermediates. If there were to be enzyme active site environments that can facilitate the retention of a significant fraction of the strengths of these isolated (gas-phase), hydrogen bonded couples, then low-barrier hydrogen bonding interactions might well play important roles in enzymatic catalysis.
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Affiliation(s)
- Jacob D Graham
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
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26
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Lewis CA, Wolfenden R. The nonenzymatic decomposition of guanidines and amidines. J Am Chem Soc 2013; 136:130-6. [PMID: 24359273 DOI: 10.1021/ja411927k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
To establish the rates and mechanisms of decomposition of guanidine and amidine derivatives in aqueous solution and the rate enhancements produced by the corresponding enzymes, we examined their rates of reaction at elevated temperatures and used the Arrhenius equation to extrapolate the results to room temperature. The similar reactivities of methylguanidine and 1,1,3,3-tetramethylguanidine and their negative entropies of activation imply that their decomposition proceeds by hydrolysis rather than elimination. The influence of changing pH on the rate of decomposition is consistent with attack by hydroxide ion on the methylguanidinium ion (k2 = 5 × 10(-6) M(-1) s(-1) at 25 °C) or with the kinetically equivalent attack by water on uncharged methylguanidine. At 25 °C and pH 7, N-methylguanidine is several orders of magnitude more stable than acetamidine, urea, or acetamide. Under the same conditions, the enzymes arginase and agmatinase accelerate substrate hydrolysis 4 × 10(14)-fold and 6 × 10(12)-fold, respectively, by mechanisms that appear to involve metal-mediated water attack. Arginine deiminase accelerates substrate hydrolysis 6 × 10(12)-fold by a mechanism that (in contrast to the mechanisms employed by arginase and agmatinase) is believed to involve attack by an active-site cysteine residue.
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Affiliation(s)
- Charles A Lewis
- Department of Biochemistry and Biophysics, University of North Carolina , Chapel Hill, North Carolina 27599, United States
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27
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The universality of enzymatic rate-temperature dependency. Trends Biochem Sci 2013; 39:1-7. [PMID: 24315123 DOI: 10.1016/j.tibs.2013.11.001] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 10/31/2013] [Accepted: 11/01/2013] [Indexed: 11/21/2022]
Abstract
Organismal adaptation to extreme temperatures yields enzymes with distinct configurational stabilities, including thermophilic and psychrophilic enzymes, which are adapted to high and low temperatures, respectively. These enzymes are widely assumed to also have unique rate-temperature dependencies. Thermophilic enzymes, for example, are considered optimal at high temperatures and effectively inactive at low temperatures due to excess rigidity. Surveying published data, we find that thermophilic, mesophilic, and psychrophilic enzymes exhibit indistinguishable rate-temperature dependencies. Furthermore, given the nonenzymatic rate-temperature dependency, all enzymes, regardless of their operation temperatures, become >10-fold less powerful catalysts per 25 °C temperature increase. Among other factors, this loss of rate acceleration may be ascribed to thermally induced vibrations compromising the active-site catalytic configuration, suggesting that many enzymes are in fact insufficiently rigid.
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28
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Biapenem inactivation by B2 metallo β-lactamases: energy landscape of the hydrolysis reaction. PLoS One 2013; 8:e55136. [PMID: 23372827 PMCID: PMC3556986 DOI: 10.1371/journal.pone.0055136] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 12/18/2012] [Indexed: 11/26/2022] Open
Abstract
Background A general mechanism has been proposed for metallo β-lactamases (MβLs), in which deprotonation of a water molecule near the Zn ion(s) results in the formation of a hydroxide ion that attacks the carbonyl oxygen of the β-lactam ring. However, because of the absence of X-ray structures that show the exact position of the antibiotic in the reactant state (RS) it has been difficult to obtain a definitive validation of this mechanism. Methodology/Principal Findings We have employed a strategy to identify the RS, which does not rely on substrate docking and/or molecular dynamics. Starting from the X-ray structure of the enzyme:product complex (the product state, PS), a QM/MM scan was used to drive the reaction uphill from product back to reactant. Since in this process also the enzyme changes from PS to RS, we actually generate the enzyme:substrate complex from product and avoid the uncertainties associated with models of the reactant state. We used this strategy to study the reaction of biapenem hydrolysis by B2 MβL CphA. QM/MM simulations were carried out under 14 different ionization states of the active site, in order to generate potential energy surfaces (PESs) corresponding to a variety of possible reaction paths. Conclusions/Significance The calculations support a model for biapenem hydrolysis by CphA, in which the nucleophile that attacks the β-lactam ring is not the water molecule located in proximity of the active site Zn, but a second water molecule, hydrogen bonded to the first one, which is used up in the reaction, and thus is not visible in the X-ray structure of the enzyme:product complex.
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29
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Schroeder GK, Zhou L, Snider MJ, Chen X, Wolfenden R. Flight of a Cytidine Deaminase Complex with an Imperfect Transition State Analogue Inhibitor: Mass Spectrometric Evidence for the Presence of a Trapped Water Molecule. Biochemistry 2012; 51:6476-86. [DOI: 10.1021/bi300516u] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gottfried K. Schroeder
- Department of Biochemistry and
Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Li Zhou
- Department of Biochemistry and
Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Mark J. Snider
- Department of Chemistry, College of Wooster, Wooster, Ohio 44691, United States
| | - Xian Chen
- Department of Biochemistry and
Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Richard Wolfenden
- Department of Biochemistry and
Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, United States
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30
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Collins KD. Why continuum electrostatics theories cannot explain biological structure, polyelectrolytes or ionic strength effects in ion–protein interactions. Biophys Chem 2012; 167:43-59. [DOI: 10.1016/j.bpc.2012.04.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 01/13/2023]
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31
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Gatti DL. Biapenem inactivation by B2 metallo β-lactamases: energy landscape of the post-hydrolysis reactions. PLoS One 2012; 7:e30079. [PMID: 22272276 PMCID: PMC3260057 DOI: 10.1371/journal.pone.0030079] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 12/13/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The first line of defense by bacteria against β-lactam antibiotics is the expression of β-lactamases, which cleave the amide bond of the β-lactam ring. In the reaction of biapenem inactivation by B2 metallo β-lactamases (MβLs), after the β-lactam ring is opened, the carboxyl group generated by the hydrolytic process and the hydroxyethyl group (common to all carbapenems) rotate around the C5-C6 bond, assuming a new position that allows a proton transfer from the hydroxyethyl group to C2, and a nucleophilic attack on C3 by the oxygen atom of the same side-chain. This process leads to the formation of a bicyclic compound, as originally observed in the X-ray structure of the metallo β-lactamase CphA in complex with product. METHODOLOGY/PRINCIPAL FINDINGS QM/MM and metadynamics simulations of the post-hydrolysis steps in solution and in the enzyme reveal that while the rotation of the hydroxyethyl group can occur in solution or in the enzyme active site, formation of the bicyclic compound occurs primarily in solution, after which the final product binds back to the enzyme. The calculations also suggest that the rotation and cyclization steps can occur at a rate comparable to that observed experimentally for the enzymatic inactivation of biapenem only if the hydrolysis reaction leaves the N4 nitrogen of the β-lactam ring unprotonated. CONCLUSIONS/SIGNIFICANCE The calculations support the existence of a common mechanism (in which ionized N4 is the leaving group) for carbapenems hydrolysis in all MβLs, and suggest a possible revision of mechanisms for B2 MβLs in which the cleavage of the β-lactam ring is associated with or immediately followed by protonation of N4. The study also indicates that the bicyclic derivative of biapenem has significant affinity for B2 MβLs, and that it may be possible to obtain clinically effective inhibitors of these enzymes by modification of this lead compound.
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Affiliation(s)
- Domenico L Gatti
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan, United States of America.
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32
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Wolfenden R. Benchmark Reaction Rates, the Stability of Biological Molecules in Water, and the Evolution of Catalytic Power in Enzymes. Annu Rev Biochem 2011; 80:645-67. [DOI: 10.1146/annurev-biochem-060409-093051] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Richard Wolfenden
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599;
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33
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Enzyme catalysis from improved packing in their transition-state structures. Curr Opin Chem Biol 2011; 14:666-70. [PMID: 20810304 DOI: 10.1016/j.cbpa.2010.08.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 08/05/2010] [Accepted: 08/05/2010] [Indexed: 11/22/2022]
Abstract
The binding of ligands to proteins can be enhanced through improved packing within the proteins that may, or may not, occur with conformational change. Enzymes can similarly improve their catalytic magic through better packing in the transition state (TS) for reaction. In principle, the improved packing demands no more than the minute shortening of non-covalent interactions throughout much of the structure of the protein (positively cooperative binding). Improved protein packing can account for the remarkably high biotin/streptavidin affinity, and perhaps also for a major part of the catalytic function of hypoxanthine-guanine phosphoribosyltransferase and purine nucleoside phosphorylase (PNP). As successive NAD(+) molecules bind to the glyceraldehyde phosphate dehydrogenase tetramer, they do so with positively cooperative binding (using the term as applied in crystallization and protein folding) that decreases at each step. This binding is negatively cooperative in the usage stemming from Monod and co-workers.
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34
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Stockbridge RB, Lewis CA, Yuan Y, Wolfenden R. Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes. Proc Natl Acad Sci U S A 2010; 107:22102-5. [PMID: 21123742 PMCID: PMC3009776 DOI: 10.1073/pnas.1013647107] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
All reactions are accelerated by an increase in temperature, but the magnitude of that effect on very slow reactions does not seem to have been fully appreciated. The hydrolysis of polysaccharides, for example, is accelerated 190,000-fold when the temperature is raised from 25 to 100 °C, while the rate of hydrolysis of phosphate monoester dianions increases 10,300,000-fold. Moreover, the slowest reactions tend to be the most heat-sensitive. These tendencies collapse, by as many as five orders of magnitude, the time that would have been required for early chemical evolution in a warm environment. We propose, further, that if the catalytic effect of a "proto-enzyme"--like that of modern enzymes--were mainly enthalpic, then the resulting rate enhancement would have increased automatically as the environment became cooler. Several powerful nonenzymatic catalysts of very slow biological reactions, notably pyridoxal phosphate and the ceric ion, are shown to meet that criterion. Taken together, these findings greatly reduce the time that would have been required for early chemical evolution, countering the view that not enough time has passed for life to have evolved to its present level of complexity.
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Affiliation(s)
- Randy B. Stockbridge
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599
| | - Charles A. Lewis
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599
| | - Yang Yuan
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599
| | - Richard Wolfenden
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599
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35
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Kamath G, Howell EE, Agarwal PK. The Tail Wagging the Dog: Insights into Catalysis in R67 Dihydrofolate Reductase. Biochemistry 2010; 49:9078-88. [DOI: 10.1021/bi1007222] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ganesh Kamath
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Elizabeth E. Howell
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Pratul K. Agarwal
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
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36
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Kamerlin SCL, Warshel A. At the dawn of the 21st century: Is dynamics the missing link for understanding enzyme catalysis? Proteins 2010; 78:1339-75. [PMID: 20099310 PMCID: PMC2841229 DOI: 10.1002/prot.22654] [Citation(s) in RCA: 345] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Enzymes play a key role in almost all biological processes, accelerating a variety of metabolic reactions as well as controlling energy transduction, the transcription, and translation of genetic information, and signaling. They possess the remarkable capacity to accelerate reactions by many orders of magnitude compared to their uncatalyzed counterparts, making feasible crucial processes that would otherwise not occur on biologically relevant timescales. Thus, there is broad interest in understanding the catalytic power of enzymes on a molecular level. Several proposals have been put forward to try to explain this phenomenon, and one that has rapidly gained momentum in recent years is the idea that enzyme dynamics somehow contributes to catalysis. This review examines the dynamical proposal in a critical way, considering basically all reasonable definitions, including (but not limited to) such proposed effects as "coupling between conformational and chemical motions," "landscape searches" and "entropy funnels." It is shown that none of these proposed effects have been experimentally demonstrated to contribute to catalysis, nor are they supported by consistent theoretical studies. On the other hand, it is clarified that careful simulation studies have excluded most (if not all) dynamical proposals. This review places significant emphasis on clarifying the role of logical definitions of different catalytic proposals, and on the need for a clear formulation in terms of the assumed potential surface and reaction coordinate. Finally, it is pointed out that electrostatic preorganization actually accounts for the observed catalytic effects of enzymes, through the corresponding changes in the activation free energies.
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Affiliation(s)
- Shina C. L. Kamerlin
- Department of Chemistry, University of Southern California, 3620 McClintock Ave., Los Angeles CA-90089, USA
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, 3620 McClintock Ave., Los Angeles CA-90089, USA
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37
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Kamerlin SCL, Mavri J, Warshel A. Examining the case for the effect of barrier compression on tunneling, vibrationally enhanced catalysis, catalytic entropy and related issues. FEBS Lett 2010; 584:2759-66. [PMID: 20433839 DOI: 10.1016/j.febslet.2010.04.062] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 04/21/2010] [Accepted: 04/22/2010] [Indexed: 10/19/2022]
Abstract
The idea that tunneling is enhanced by the compression of the donor-acceptor distance has attracted significant interest. In particular, recent studies argued that this proposal is consistent with pressure effects on enzymatic reactions, and that the observed pressure effects support the idea of vibrationally enhanced catalysis. However, a careful analysis of the current works reveals serious inconsistencies in the evidence presented to support these hypotheses. Apparently, tunneling decreases upon compression, and external pressure does not lead to the applicable compression of the free energy surface. Additionally, pressure experiments do not provide actual evidence for vibrationally enhanced catalysis. Finally, the temperature dependence of the entropy change in hydride transfer reactions is shown to reflect simple electrostatic effects.
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38
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Truhlar DG. Tunneling in enzymatic and nonenzymatic hydrogen transfer reactions. J PHYS ORG CHEM 2010. [DOI: 10.1002/poc.1676] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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39
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Gloster TM, Davies GJ. Glycosidase inhibition: assessing mimicry of the transition state. Org Biomol Chem 2010; 8:305-20. [PMID: 20066263 PMCID: PMC2822703 DOI: 10.1039/b915870g] [Citation(s) in RCA: 188] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 09/30/2009] [Indexed: 12/15/2022]
Abstract
Glycoside hydrolases, the enzymes responsible for hydrolysis of the glycosidic bond in di-, oligo- and polysaccharides, and glycoconjugates, are ubiquitous in Nature and fundamental to existence. The extreme stability of the glycosidic bond has meant these enzymes have evolved into highly proficient catalysts, with an estimated 10(17) fold rate enhancement over the uncatalysed reaction. Such rate enhancements mean that enzymes bind the substrate at the transition state with extraordinary affinity; the dissociation constant for the transition state is predicted to be 10(-22) M. Inhibition of glycoside hydrolases has widespread application in the treatment of viral infections, such as influenza and HIV, lysosomal storage disorders, cancer and diabetes. If inhibitors are designed to mimic the transition state, it should be possible to harness some of the transition state affinity, resulting in highly potent and specific drugs. Here we examine a number of glycosidase inhibitors which have been developed over the past half century, either by Nature or synthetically by man. A number of criteria have been proposed to ascertain which of these inhibitors are true transition state mimics, but these features have only be critically investigated in a very few cases.
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Affiliation(s)
- Tracey M. Gloster
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, UK. ; ; Fax: +44 1904 328266; Tel: +44 1904 328260
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Gideon J. Davies
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, UK. ; ; Fax: +44 1904 328266; Tel: +44 1904 328260
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40
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Tao P, Gatti DL, Schlegel HB. The Energy Landscape of 3-Deoxy-d-manno-octulosonate 8-Phosphate Synthase. Biochemistry 2009; 48:11706-14. [DOI: 10.1021/bi901341h] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Peng Tao
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202
| | - Domenico L. Gatti
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - H. Bernhard Schlegel
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202
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41
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Collot AG, Courtney M, Coyne D, Eustace SE, More O’Ferrall RA. Binding Catalysis and Inhibition by Metal Ions and Protons in the Enolization of Phenylacetylpyrazine. J Org Chem 2009; 74:3356-69. [DOI: 10.1021/jo802650s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Anne-Gaelle Collot
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Michael Courtney
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Dara Coyne
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Stephen E. Eustace
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Rory A. More O’Ferrall
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
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42
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Characterization of the phenylurea hydrolases A and B: founding members of a novel amidohydrolase subgroup. Biochem J 2009; 418:431-41. [DOI: 10.1042/bj20081488] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mycobacterium brisbanense strain JK1, a bacterium capable of degrading the herbicide diuron, was isolated from herbicide-exposed soil. A gene/enzyme system with diuron hydrolase activity was isolated from this strain and named PUH (phenylurea hydrolase) B (puhB/PuhB) because of its close similarity to the previously characterized PUH A (puhA/PuhA). Both PUHs were heterologously expressed, purified and characterized. The PUHs were found to oligomerize as hexamers in solution, with each monomer containing a mononuclear Zn2+ active site. Sequence analysis showed that these enzymes belong to the metal-dependent amidohydrolase superfamily, although they contain a hitherto unreported Asn-X-His metal-binding motif and appear to form a novel sub-group within this superfamily. The effects of temperature and solvent on the enzymes were characterized. Determination of the kinetic parameters of the PUHs was used alongside Brønsted plots to develop a plausible catalytic mechanism, which is similar to that used by urease. In addition to the primary PUH activity, both enzymes are catalytically promiscuous, efficiently hydrolysing esters, carbamates and phosphotriesters. In fact, an analogue of diuron, in which the C–N bond was replaced by a C–O bond, was found to be turned over as efficiently as diuron, suggesting that the substrate specificity is predominantly determined by steric factors. The discovery of PuhA and PuhB on separate continents, and the absence of any other close homologues in the available sequence databases, poses a challenging question regarding the evolutionary origins of these enzymes.
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43
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β-d-Xylosidase from Selenomonas ruminantium: Thermodynamics of Enzyme-Catalyzed and Noncatalyzed Reactions. Appl Biochem Biotechnol 2008; 155:330-46. [DOI: 10.1007/s12010-008-8397-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2008] [Accepted: 10/06/2008] [Indexed: 10/21/2022]
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44
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Yeast sterol C24-methyltransferase: role of highly conserved tyrosine-81 in catalytic competence studied by site-directed mutagenesis and thermodynamic analysis. Arch Biochem Biophys 2008; 477:313-23. [PMID: 18555004 DOI: 10.1016/j.abb.2008.05.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/23/2008] [Accepted: 05/23/2008] [Indexed: 11/22/2022]
Abstract
The role of Try-81 in the reaction catalyzed by Saccharomyces cerevisiae sterol 24-C-methyltransferase (Erg6p) was investigated kinetically and for product differences against a panel of position-81 mutants in which Tyr was substituted with Trp, Phe, Ile, Leu, Val and Ala. The residue chosen for mutation is one that was reported previously to accept fecosterol and yield a set 24-ethyl (idene) sterol products typical of plants, showing the amino acid residue is located close to the transient C25 carbocation intermediate in the active site. One group of mutants (aromatic) tested with the natural substrate zymosterol accelerated the C-methylation reaction (k(cat)/K(m)) whereas the other group of mutants (aliphatics) decreased catalytic competence as the amino acid side chain was downsized. Mutating to aromatic and assaying with the substrate analog designed as a suicide substrate 26,27-dehydrozymosterol favored C26-monol formation, whereas mutating to the aliphatic of smaller size favored C26-diol formation (a measure of enzyme alkylation). In no case was zymosterol converted to an intermediate that formed a C25-diol. Thermodynamic analysis (determination of E(a), DeltaG(double dagger), DeltaH(double dagger) and TDeltaS(double dagger)) for the C-methylation reaction performed by these enzymes assayed with the substrate and its analog or zymosterol paired with the "charged' high energy intermediate (HEI) analogs 24(R,S)25,epiminolanosterol and 25-azalanosterol or "neutral" membrane insert ergosterol showed that mutation to aromatics can reduce inhibitor potency (measured as K(m)/K(i)), yet catalysis can improve in Trp81 by the introduction of a gain in free energy associated with stabilization of the transition state of a rate-controlling step directed toward turnover. Alternatively, mutation to the smaller aliphatic amino acid side chains led to a destabilization in the active site structure which was accompanied by increases in the partition ratios associated with abortive complex formation. The results are explained by consideration of the functional differences attributed to Tyr81 substitution to aromatics and aliphatics of different size involved with cation-pi or hydrogen bonding interactions and in the activation barriers required of differing side chain conformations to orient the reactants in the direction of turnover versus enzyme inactivation.
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45
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Olsson MHM, Parson WW, Warshel A. Dynamical contributions to enzyme catalysis: critical tests of a popular hypothesis. Chem Rev 2007; 106:1737-56. [PMID: 16683752 DOI: 10.1021/cr040427e] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mats H M Olsson
- Department of Chemistry, University of Southern California, 3620 McClintock Avenue, Los Angeles, California 90089-1062, USA.
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46
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Kumasaka T, Yamamoto M, Furuichi M, Nakasako M, Teh AH, Kimura M, Yamaguchi I, Ueki T. Crystal structures of blasticidin S deaminase (BSD): implications for dynamic properties of catalytic zinc. J Biol Chem 2007; 282:37103-11. [PMID: 17959604 DOI: 10.1074/jbc.m704476200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The set of blasticidin S (BS) and blasticidin S deaminase (BSD) is a widely used selectable marker for gene transfer experiments. BSD is a member of the cytidine deaminase (CDA) family; it is a zinc-dependent enzyme with three cysteines and one water molecule as zinc ligands. The crystal structures of BSD were determined in six states (i.e. native, substrate-bound, product-bound, cacodylate-bound, substrate-bound E56Q mutant, and R90K mutant). In the structures, the zinc position and coordination structures vary. The substrate-bound structure shows a large positional and geometrical shift of zinc with a double-headed electron density of the substrate that seems to be assigned to the amino and hydroxyl groups of the substrate and product, respectively. In this intermediate-like structure, the steric hindrance of the hydroxyl group pushes the zinc into the triangular plane consisting of three cysteines with a positional shift of approximately 0.6 A, and the fifth ligand water approaches the opposite direction of the substrate with a shift of 0.4 A. Accordingly, the zinc coordination is changed from tetrahedral to trigonal bipyramidal, and its coordination distance is extended between zinc and its intermediate. The shift of zinc and the recruited water is also observed in the structure of the inactivated E56Q mutant. This novel observation is different in two-cysteine cytidine deaminase Escherichia coli CDA and might be essential for the reaction mechanism in BSD, since it is useful for the easy release of the product by charge compensation and for the structural change of the substrate.
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Affiliation(s)
- Takashi Kumasaka
- Department of Life Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8501, Japan.
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47
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Callahan BP, Miller BG. OMP decarboxylase--An enigma persists. Bioorg Chem 2007; 35:465-9. [PMID: 17889251 DOI: 10.1016/j.bioorg.2007.07.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Accepted: 07/26/2007] [Indexed: 11/22/2022]
Abstract
In 1995, Radzicka and Wolfenden reported that the rate enhancement produced by orotidine 5'-phosphate decarboxylase (ODCase) approaches 10(17), making this enzyme the most effective pure protein catalyst known in Nature [A. Radzicka, R. Wolfenden, Science 267 (1995) 90-93]. Over the last 12 years, there have been many hypotheses put forward to explain that impressive effect. In this perspective, we provide a summary of the reaction pathways under consideration for ODCase, highlight the supporting and refuting data, and suggest experiments designed to further test each of the candidate pathways.
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Affiliation(s)
- Brian P Callahan
- Division of Infectious Disease, Wadsworth Center--NYS-DOH, Albany, NY 12202, USA.
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48
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Warshel A, Sharma PK, Kato M, Xiang Y, Liu H, Olsson MHM. Electrostatic basis for enzyme catalysis. Chem Rev 2007; 106:3210-35. [PMID: 16895325 DOI: 10.1021/cr0503106] [Citation(s) in RCA: 966] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Arieh Warshel
- Department of Chemistry, University of Southern California, SGM Building 418, 3620 McClintock Avenue, Los Angeles, California 90089-1062, USA.
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49
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Estiu G, Suárez D, Merz KM. Quantum mechanical and molecular dynamics simulations of ureases and Zn beta-lactamases. J Comput Chem 2007; 27:1240-62. [PMID: 16773613 DOI: 10.1002/jcc.20411] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Herein we briefly review theoretical contributions that have increased our understanding of the structure and function of metallo-beta-lactamases and ureases. Both are bimetallic metalloenzymes, with the former containing two zinc ions and the latter containing two nickel ions. We describe the use of several different methodologies, including quantum chemical calculations, molecular dynamic simulations, as well as mixed QM/MM approaches and how they have impacted our understanding of the structure and function of metallo-beta-lactamases and ureases.
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Affiliation(s)
- Guillermina Estiu
- Department of Chemistry, Quantum Theory Project, University of Florida, 2328 New Physics Building, P.O. Box 118435, Gainesville, Florida 32611-8435, USA
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50
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Matsubara T, Dupuis M, Aida M. Ab Initio ONIOM−Molecular Dynamics (MD) Study on the Deamination Reaction by Cytidine Deaminase. J Phys Chem B 2007; 111:9965-74. [PMID: 17661509 DOI: 10.1021/jp072732k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We applied the ONIOM-molecular dynamics (MD) method to the hydrolytic deamination of cytidine by cytidine deaminase, which is an essential step of the activation process of the anticancer drug inside the human body. The direct MD simulations were performed for the realistic model of cytidine deaminase by calculating the energy and its gradient by the ab initio ONIOM method on the fly. The ONIOM-MD calculations including the thermal motion show that the neighboring amino acid residue is an important factor of the environmental effects and significantly affects not only the geometry and energy of the substrate trapped in the pocket of the active site but also the elementary step of the catalytic reaction. We successfully simulate the second half of the catalytic cycle, which has been considered to involve the rate-determining step, and reveal that the rate-determining step is the release of the NH3 molecule.
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Affiliation(s)
- Toshiaki Matsubara
- Center for Quantum Life Sciences and Graduate School of Science, Hiroshima University, 1-3-1, Kagamiyama, Higashi-Hiroshima 739-8530, Japan.
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