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Ju Z, Xu J, Li Z, Fang J, Li M, Howell DC, Chen FE. Benzaldehyde lyase-catalyzed enantioselective C–C bond formation and cleavage: A review. GREEN SYNTHESIS AND CATALYSIS 2022. [DOI: 10.1016/j.gresc.2022.05.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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2
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Yang Q, Guo X, Liu Y, Jiang H. Biocatalytic C-C Bond Formation for One Carbon Resource Utilization. Int J Mol Sci 2021; 22:ijms22041890. [PMID: 33672882 PMCID: PMC7918591 DOI: 10.3390/ijms22041890] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/31/2021] [Accepted: 02/05/2021] [Indexed: 12/22/2022] Open
Abstract
The carbon-carbon bond formation has always been one of the most important reactions in C1 resource utilization. Compared to traditional organic synthesis methods, biocatalytic C-C bond formation offers a green and potent alternative for C1 transformation. In recent years, with the development of synthetic biology, more and more carboxylases and C-C ligases have been mined and designed for the C1 transformation in vitro and C1 assimilation in vivo. This article presents an overview of C-C bond formation in biocatalytic C1 resource utilization is first provided. Sets of newly mined and designed carboxylases and ligases capable of catalyzing C-C bond formation for the transformation of CO2, formaldehyde, CO, and formate are then reviewed, and their catalytic mechanisms are discussed. Finally, the current advances and the future perspectives for the development of catalysts for C1 resource utilization are provided.
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Affiliation(s)
- Qiaoyu Yang
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China; (Q.Y.); (X.G.)
- National Technology Innovation Center of Synthetic Biology, Tianjin 300308, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoxian Guo
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China; (Q.Y.); (X.G.)
- National Technology Innovation Center of Synthetic Biology, Tianjin 300308, China
| | - Yuwan Liu
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China; (Q.Y.); (X.G.)
- National Technology Innovation Center of Synthetic Biology, Tianjin 300308, China
- Correspondence: (Y.L.); (H.J.)
| | - Huifeng Jiang
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China; (Q.Y.); (X.G.)
- National Technology Innovation Center of Synthetic Biology, Tianjin 300308, China
- Correspondence: (Y.L.); (H.J.)
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3
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Poust S, Piety J, Bar-Even A, Louw C, Baker D, Keasling JD, Siegel JB. Mechanistic Analysis of an Engineered Enzyme that Catalyzes the Formose Reaction. Chembiochem 2015; 16:1950-1954. [PMID: 26109266 DOI: 10.1002/cbic.201500228] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Indexed: 11/08/2022]
Abstract
An enzyme that catalyzes the formose reaction, termed "formolase", was recently engineered through a combination of computational protein design and directed evolution. We have investigated the kinetic role of the computationally designed residues and further characterized the enzyme's product profile. Kinetic studies illustrated that the computationally designed mutations were synergistic in their contributions towards enhancing activity. Mass spectrometry revealed that the engineered enzyme produces two products of the formose reaction-dihydroxyacetone and glycolaldehyde-with the product profile dependent on the formaldehyde concentration. We further explored the effects of this product profile on the thermodynamics and yield of the overall carbon assimilation from the formolase pathway to help guide future efforts to engineer this pathway.
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Affiliation(s)
- Sean Poust
- Department of Chemical and Biomolecular Engineering, University of California, 201 Gilman Hall, Berkeley, CA 94720-1462 (USA).,Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, 5885 Hollis Street, Emeryville, CA 94608 (USA)
| | - James Piety
- Department of Chemical and Biomolecular Engineering, University of California, 201 Gilman Hall, Berkeley, CA 94720-1462 (USA).,Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, 5885 Hollis Street, Emeryville, CA 94608 (USA)
| | - Arren Bar-Even
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm (Germany)
| | - Catherine Louw
- Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195 (USA)
| | - David Baker
- Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195 (USA)
| | - Jay D Keasling
- Department of Chemical and Biomolecular Engineering, University of California, 201 Gilman Hall, Berkeley, CA 94720-1462 (USA).,Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, 5885 Hollis Street, Emeryville, CA 94608 (USA)
| | - Justin B Siegel
- Departments of Chemistry and Biochemistry and Molecular Medicine, Genome Center, University of California, 451 Health Sciences Drive, Davis, CA 95616 (USA).,Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195 (USA)
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Abstract
AbstractDecarboxylation reactions on enzymes are consistently much faster than their nonenzymic counterparts. Examination of the potential for catalysis in the nonenzymic reactions revealed that the reaction is slowed by the failure of CO2 to be launched into solution upon C–C bond cleavage. Catalysts can facilitate the reaction by weakening the C–CO2H bond but this is not sufficient. Converting the precursor of CO2 into a precursor of bicarbonate facilitates the forward reaction as does protonation of the nascent carbanion.
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Affiliation(s)
- Ronald Kluger
- 1Department of Chemistry, University of Toronto, Toronto ON M5S 3H6, Canada
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5
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Jordan F, Nemeria NS. Progress in the experimental observation of thiamin diphosphate-bound intermediates on enzymes and mechanistic information derived from these observations. Bioorg Chem 2014; 57:251-262. [PMID: 25228115 DOI: 10.1016/j.bioorg.2014.08.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 08/11/2014] [Indexed: 11/26/2022]
Abstract
Thiamin diphosphate (ThDP), the vitamin B1 coenzyme is an excellent representative of coenzymes, which carry out electrophilic catalysis by forming a covalent complex with their substrates. The function of ThDP is to greatly increase the acidity of two carbon acids by stabilizing their conjugate bases, the ylide/carbene/C2-carbanion of the thiazolium ring and the C2α-carbanion/enamine, once the substrate binds to ThDP. In recent years, several ThDP-bound intermediates on such pathways have been characterized by both solution and solid-state methods. Prominent among these advances are X-ray crystallographic results identifying both oxidative and non-oxidative intermediates, rapid chemical quench followed by NMR detection of several intermediates which are stable under acidic conditions, solid-state NMR and circular dichroism detection of the states of ionization and tautomerization of the 4'-aminopyrimidine moiety of ThDP in some of the intermediates. These methods also enabled in some cases determination of the rate-limiting step in the complex series of steps. This review is an update of a review with the same title published by the authors in 2005 in this Journal. Much progress has been made in the intervening decade in the identification of the intermediates and their application to gain additional mechanistic insight.
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Affiliation(s)
- Frank Jordan
- Department of Chemistry, Rutgers University, Newark, NJ 07102, USA.
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6
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Patel H, Nemeria NS, Andrews FH, McLeish MJ, Jordan F. Identification of charge transfer transitions related to thiamin-bound intermediates on enzymes provides a plethora of signatures useful in mechanistic studies. Biochemistry 2014; 53:2145-52. [PMID: 24628377 PMCID: PMC3985856 DOI: 10.1021/bi4015743] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Identification
of enzyme-bound intermediates via their spectroscopic
signatures, which then allows direct monitoring of the kinetic fate
of these intermediates, poses a continuing challenge. As an electrophilic
covalent catalyst, the thiamin diphosphate (ThDP) coenzyme forms a
number of noncovalent and covalent intermediates along its reaction
pathways, and multiple UV–vis and circular dichroism (CD) bands
have been identified at Rutgers pertinent to several among them. These
electronic transitions fall into two classes: those for which the
conjugated system provides a reasonable guide to the observed λmax and others in which there is no corresponding conjugated
system and the observed CD bands are best ascribed to charge transfer
(CT) transitions. Herein is reported the reaction of four ThDP enzymes
with alternate substrates: (a) acetyl pyruvate, its methyl ester,
and fluoropyruvate, these providing the shortest side chains attached
at the thiazolium C2 atom and leading to CT bands with λmax values of >390 nm, not pertinent to any on-pathway conjugated
systems (estimated λmax values of <330 nm), and
(b) (E)-4-(4-chlorophenyl)-2-oxo-3-butenoic acid
displaying both a conjugated enamine (430 nm) and a CT transition
(480 nm). We suggest that the CT transitions result from an interaction
of the π bond on the ThDP C2 side chain as a donor, and the
positively charged thiazolium ring as an acceptor, and correspond
to covalent ThDP-bound intermediates. Time resolution of these bands
allows the rate constants for individual steps to be determined. These
CD methods can be applied to the entire ThDP superfamily of enzymes
and should find applications with other enzymes.
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Affiliation(s)
- Hetalben Patel
- Department of Chemistry, Rutgers, the State University of New Jersey , Newark, New Jersey 07102, United States
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Jordan F, Patel H. Catalysis in Enzymatic Decarboxylations: Comparison of Selected Cofactor-dependent and Cofactor-independent Examples. ACS Catal 2013; 3:1601-1617. [PMID: 23914308 DOI: 10.1021/cs400272x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
This review is focused on three types of enzymes decarboxylating very different substrates: (1) Thiamin diphosphate (ThDP)-dependent enzymes reacting with 2-oxo acids; (2) Pyridoxal phosphate (PLP)-dependent enzymes reacting with α-amino acids; and (3) An enzyme with no known co-factors, orotidine 5'-monophosphate decarboxylase (OMPDC). While the first two classes have been much studied for many years, during the past decade studies of both classes have revealed novel mechanistic insight challenging accepted understanding. The enzyme OMPDC has posed a challenge to the enzymologist attempting to explain a 1017-fold rate acceleration in the absence of cofactors or even metal ions. A comparison of the available evidence on the three types of decarboxylases underlines some common features and more differences. The field of decarboxylases remains an interesting and challenging one for the mechanistic enzymologist notwithstanding the large amount of information already available.
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Affiliation(s)
- Frank Jordan
- Department of Chemistry, Rutgers, The State University of New Jersey, 73 Warren Street, Newark,
New Jersey 07102, United States
| | - Hetalben Patel
- Department of Chemistry, Rutgers, The State University of New Jersey, 73 Warren Street, Newark,
New Jersey 07102, United States
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Brandt GS, Kneen MM, Petsko GA, Ringe D, McLeish MJ. Active-Site Engineering of Benzaldehyde Lyase Shows That a Point Mutation Can Confer Both New Reactivity and Susceptibility to Mechanism-Based Inhibition. J Am Chem Soc 2009; 132:438-9. [DOI: 10.1021/ja907064w] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gabriel S. Brandt
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, and Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202
| | - Malea M. Kneen
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, and Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202
| | - Gregory A. Petsko
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, and Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202
| | - Dagmar Ringe
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, and Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202
| | - Michael J. McLeish
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, and Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202
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Kokova M, Zavrel M, Tittmann K, Spiess AC, Pohl M. Investigation of the carboligase activity of thiamine diphosphate-dependent enzymes using kinetic modeling and NMR spectroscopy. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.molcatb.2009.02.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Schmidt T, Zavrel M, Spieß A, Ansorge-Schumacher M. Biochemical peculiarities of benzaldehyde lyase from Pseudomonas fluorescens Biovar I in the dependency on pH and cosolvent concentration. Bioorg Chem 2009; 37:84-9. [DOI: 10.1016/j.bioorg.2009.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2008] [Revised: 03/04/2009] [Accepted: 03/04/2009] [Indexed: 11/24/2022]
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Brandt GS, Kneen MM, Chakraborty S, Baykal AT, Nemeria N, Yep A, Ruby DI, Petsko GA, Kenyon GL, McLeish MJ, Jordan F, Ringe D. Snapshot of a reaction intermediate: analysis of benzoylformate decarboxylase in complex with a benzoylphosphonate inhibitor. Biochemistry 2009; 48:3247-57. [PMID: 19320438 DOI: 10.1021/bi801950k] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Benzoylformate decarboxylase (BFDC) is a thiamin diphosphate- (ThDP-) dependent enzyme acting on aromatic substrates. In addition to its metabolic role in the mandelate pathway, BFDC shows broad substrate specificity coupled with tight stereo control in the carbon-carbon bond-forming reverse reaction, making it a useful biocatalyst for the production of chiral alpha-hydroxy ketones. The reaction of methyl benzoylphosphonate (MBP), an analogue of the natural substrate benzoylformate, with BFDC results in the formation of a stable analogue (C2alpha-phosphonomandelyl-ThDP) of the covalent ThDP-substrate adduct C2alpha-mandelyl-ThDP. Formation of the stable adduct is confirmed both by formation of a circular dichroism band characteristic of the 1',4'-iminopyrimidine tautomeric form of ThDP (commonly observed when ThDP forms tetrahedral complexes with its substrates) and by high-resolution mass spectrometry of the reaction mixture. In addition, the structure of BFDC with the MBP inhibitor was solved by X-ray crystallography to a spatial resolution of 1.37 A (PDB ID 3FSJ). The electron density clearly shows formation of a tetrahedral adduct between the C2 atom of ThDP and the carbonyl carbon atom of the MBP. This adduct resembles the intermediate from the penultimate step of the carboligation reaction between benzaldehyde and acetaldehyde. The combination of real-time kinetic information via stopped-flow circular dichroism with steady-state data from equilibrium circular dichroism measurements and X-ray crystallography reveals details of the first step of the reaction catalyzed by BFDC. The MBP-ThDP adduct on BFDC is compared to the recently solved structure of the same adduct on benzaldehyde lyase, another ThDP-dependent enzyme capable of catalyzing aldehyde condensation with high stereospecificity.
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Affiliation(s)
- Gabriel S Brandt
- Department of Chemistry, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
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13
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Nemeria NS, Chakraborty S, Balakrishnan A, Jordan F. Reaction mechanisms of thiamin diphosphate enzymes: defining states of ionization and tautomerization of the cofactor at individual steps. FEBS J 2009; 276:2432-46. [PMID: 19476485 DOI: 10.1111/j.1742-4658.2009.06964.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We summarize the currently available information regarding the state of ionization and tautomerization of the 4'-aminopyrimidine ring of the thiamine diphosphate on enzymes requiring this coenzyme. This coenzyme forms a series of covalent intermediates with its substrates as an electrophilic catalyst, and the coenzyme itself also carries out intramolecular proton transfers, which is virtually unprecedented in coenzyme chemistry. An understanding of the state of ionization and tautomerization of the 4'-aminopyrimidine ring in each of these intermediates provides important details about proton movements during catalysis. CD spectroscopy, both steady-state and time-resolved, has proved crucial for obtaining this information because no other experimental method has provided such atomic detail so far.
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Affiliation(s)
- Natalia S Nemeria
- Department of Chemistry, Rutgers, The State University of New Jersey, Newark, NJ, USA.
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Chakraborty S, Nemeria NS, Balakrishnan A, Brandt GS, Kneen MM, Yep A, McLeish MJ, Kenyon GL, Petsko GA, Ringe D, Jordan F. Detection and time course of formation of major thiamin diphosphate-bound covalent intermediates derived from a chromophoric substrate analogue on benzoylformate decarboxylase. Biochemistry 2009; 48:981-94. [PMID: 19140682 DOI: 10.1021/bi801810h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of the enzyme benzoylformate decarboxylase (BFDC), which carries out a typical thiamin diphosphate (ThDP)-dependent nonoxidative decarboxylation reaction, was studied with the chromophoric alternate substrate (E)-2-oxo-4(pyridin-3-yl)-3-butenoic acid (3-PKB). Addition of 3-PKB resulted in the appearance of two transient intermediates formed consecutively, the first one to be formed a predecarboxylation ThDP-bound intermediate with lambda(max) at 477 nm, and the second one corresponding to the first postdecarboxylation intermediate the enamine with lambda(max) at 437 nm. The time course of formation/depletion of the PKB-ThDP covalent complex and of the enamine showed that decarboxylation was slower than formation of the PKB-ThDP covalent adduct. When the product of decarboxylation 3-(pyridin-3-yl)acrylaldehyde (PAA) was added to BFDC, again an absorbance with lambda(max) at 473 nm was formed, corresponding to the tetrahedral adduct of PAA with ThDP. Addition of well-formed crystals of BFDC to a solution of PAA resulted in a high resolution (1.34 A) structure of the BFDC-bound adduct of ThDP with PAA confirming the tetrahedral nature at the C2alpha atom, rather than of the enamine, and supporting the assignment of the lambda(max) at 473 nm to the PAA-ThDP adduct. The structure of the PAA-ThDP covalent complex is the first example of a product-ThDP adduct on BFDC. Similar studies with 3-PKB indicated that decarboxylation had taken place. Evidence was also obtained for the slow formation of the enamine intermediate when BFDC was incubated with benzaldehyde, the product of the decarboxylation reaction thus confirming its presence on the reaction pathway.
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Affiliation(s)
- Sumit Chakraborty
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, USA
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Brandt GS, Nemeria N, Chakraborty S, McLeish MJ, Yep A, Kenyon GL, Petsko GA, Jordan F, Ringe D. Probing the active center of benzaldehyde lyase with substitutions and the pseudosubstrate analogue benzoylphosphonic acid methyl ester. Biochemistry 2008; 47:7734-43. [PMID: 18570438 DOI: 10.1021/bi8004413] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Benzaldehyde lyase (BAL) catalyzes the reversible cleavage of ( R)-benzoin to benzaldehyde utilizing thiamin diphosphate and Mg (2+) as cofactors. The enzyme is important for the chemoenzymatic synthesis of a wide range of compounds via its carboligation reaction mechanism. In addition to its principal functions, BAL can slowly decarboxylate aromatic amino acids such as benzoylformic acid. It is also intriguing mechanistically due to the paucity of acid-base residues at the active center that can participate in proton transfer steps thought to be necessary for these types of reactions. Here methyl benzoylphosphonate, an excellent electrostatic analogue of benzoylformic acid, is used to probe the mechanism of benzaldehyde lyase. The structure of benzaldehyde lyase in its covalent complex with methyl benzoylphosphonate was determined to 2.49 A (Protein Data Bank entry 3D7K ) and represents the first structure of this enzyme with a compound bound in the active site. No large structural reorganization was detected compared to the complex of the enzyme with thiamin diphosphate. The configuration of the predecarboxylation thiamin-bound intermediate was clarified by the structure. Both spectroscopic and X-ray structural studies are consistent with inhibition resulting from the binding of MBP to the thiamin diphosphate in the active centers. We also delineated the role of His29 (the sole potential acid-base catalyst in the active site other than the highly conserved Glu50) and Trp163 in cofactor activation and catalysis by benzaldehyde lyase.
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Affiliation(s)
- Gabriel S Brandt
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, USA
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Jordan F, Nemeria NS. Experimental observation of thiamin diphosphate-bound intermediates on enzymes and mechanistic information derived from these observations. Bioorg Chem 2005; 33:190-215. [PMID: 15888311 PMCID: PMC4189838 DOI: 10.1016/j.bioorg.2005.02.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 02/08/2005] [Accepted: 02/10/2005] [Indexed: 11/27/2022]
Abstract
Thiamin diphosphate (ThDP), the vitamin B1 coenzyme, is an excellent representative of coenzymes, which carry out electrophilic catalysis by forming a covalent complex with their substrates. The function of ThDP is to greatly increase the acidity of two carbon acids by stabilizing their conjugate bases, the ylide/C2-carbanion of the thiazolium ring and the C2alpha-carbanion (or enamine) once the substrate binds to ThDP. In recent years, several ThDP-bound intermediates on such pathways have been characterized by both solution and solid-state (X-ray) methods. Prominent among these advances are X-ray crystallographic results identifying both oxidative and non-oxidative intermediates, rapid chemical quench followed by NMR detection of a several intermediates which are stable under acidic conditions, and circular dichroism detection of the 1',4'-imino tautomer of ThDP in some of the intermediates. Some of these methods also enable the investigator to determine the rate-limiting step in the complex series of steps.
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Affiliation(s)
- Frank Jordan
- Department of Chemistry, Rutgers University, Newark, NJ 07102, USA
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