1
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Papadopoulou A, Meyer F, Buller RM. Engineering Fe(II)/α-Ketoglutarate-Dependent Halogenases and Desaturases. Biochemistry 2023; 62:229-240. [PMID: 35446547 DOI: 10.1021/acs.biochem.2c00115] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Fe(II)/α-ketoglutarate-dependent dioxygenases (α-KGDs) are widespread enzymes in aerobic biology and serve a remarkable array of biological functions, including roles in collagen biosynthesis, plant and animal development, transcriptional regulation, nucleic acid modification, and secondary metabolite biosynthesis. This functional diversity is reflected in the enzymes' catalytic flexibility as α-KGDs can catalyze an intriguing set of synthetically valuable reactions, such as hydroxylations, halogenations, and desaturations, capturing the interest of scientists across disciplines. Mechanistically, all α-KGDs are understood to follow a similar activation pathway to generate a substrate radical, yet how individual members of the enzyme family direct this key intermediate toward the different reaction outcomes remains elusive, triggering structural, computational, spectroscopic, kinetic, and enzyme engineering studies. In this Perspective, we will highlight how first enzyme and substrate engineering examples suggest that the chemical reaction pathway within α-KGDs can be intentionally tailored using rational design principles. We will delineate the structural and mechanistic investigations of the reprogrammed enzymes and how they begin to inform about the enzymes' structure-function relationships that determine chemoselectivity. Application of this knowledge in future enzyme and substrate engineering campaigns will lead to the development of powerful C-H activation catalysts for chemical synthesis.
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Affiliation(s)
- Athena Papadopoulou
- Competence Center for Biocatalysis, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820 Wädenswil, Switzerland
| | - Fabian Meyer
- Competence Center for Biocatalysis, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820 Wädenswil, Switzerland
| | - Rebecca M Buller
- Competence Center for Biocatalysis, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820 Wädenswil, Switzerland
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2
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Vennelakanti V, Mehmood R, Kulik HJ. Are Vanadium Intermediates Suitable Mimics in Non-Heme Iron Enzymes? An Electronic Structure Analysis. ACS Catal 2022. [DOI: 10.1021/acscatal.2c01143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vyshnavi Vennelakanti
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Rimsha Mehmood
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Heather J. Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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3
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Niu X, Zhang J, Xue X, Wang D, Wang L, Gao Q. Deacetoxycephalosporin C synthase (expandase): Research progress and application potential. Synth Syst Biotechnol 2021; 6:396-401. [PMID: 34901478 PMCID: PMC8626558 DOI: 10.1016/j.synbio.2021.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 12/02/2022] Open
Abstract
Cephalosporins play an indispensable role against bacterial infections. Deacetyloxycephalosporin C synthase (DAOCS), also called expandase, is a key enzyme in cephalosporin biosynthesis that epoxides penicillin to form the hexavalent thiazide ring of cephalosporin. DAOCS in fungus Acremonium chrysogenum was identified as a bifunctional enzyme with both ring expansion and hydroxylation, whereas two separate enzymes in bacteria catalyze these two reactions. In this review, we briefly summarize its source and function, improvement of the conversion rate of penicillin to deacetyloxycephalosporin C through enzyme modification, crystallography features, the prediction of the active site, and application perspective.
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Affiliation(s)
- Xiaofan Niu
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, China
| | - Jian Zhang
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, China.,Tianjin Microbial Metabolism and Fermentation Process Control Technology Engineering Center, Tianjin, 300457, China
| | - Xianli Xue
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, China.,Tianjin Microbial Metabolism and Fermentation Process Control Technology Engineering Center, Tianjin, 300457, China
| | - Depei Wang
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, China.,National Demonstration Center for Experimental Bioengineering Education (Tianjin University of Science and Technology), Tianjin, 300457, China.,Tianjin Microbial Metabolism and Fermentation Process Control Technology Engineering Center, Tianjin, 300457, China
| | - Lin Wang
- College of Artificial Intelligence, Tianjin University of Science and Technology, Tianjin, 300457, China
| | - Qiang Gao
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, China.,National Demonstration Center for Experimental Bioengineering Education (Tianjin University of Science and Technology), Tianjin, 300457, China.,Tianjin Microbial Metabolism and Fermentation Process Control Technology Engineering Center, Tianjin, 300457, China
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4
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Liu Y, Shi J, Liu Y. Mechanistic Insights into the Oxidative Ring Expansion from Penicillin N to Deacetoxycephalosporin C Catalyzed by a Nonheme Iron(II) and α-KG-Dependent Oxygenase. Inorg Chem 2020; 59:12218-12231. [PMID: 32822181 DOI: 10.1021/acs.inorgchem.0c01211] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Deacetoxycephalosporin C synthase (DAOCS) is a nonheme iron(II) and 2-oxoglutarate (α-KG)-dependent oxygenase that catalyzes the oxidative ring expansion of penicillin N (penN) to deacetoxycephalosporin C (DAOC). Earlier reported crystal structures of DAOCS indicated that the substrate penicillin binds at the same site of succinate, leading to the proposal of the unusual "ping-pong" mechanism. However, more recent data provided evidence of the formation of ternary DAOCS·α-KG·penN complex, and thus DAOCS should follow the usual consensus mechanism of α-KG-dependent nonheme iron(II) oxygenases. Nevertheless, how DAOCS catalyzes the ring expansion is unknown. In this paper, on the basis of the crystal structure, we constructed two reactant models and performed a series of combined quantum mechanics/molecular mechanics (QM/MM) calculations to illuminate the catalysis of DAOCS. The binding mode of substrate was found to be crucial in determining which hydrogen atom in two methyl groups is first abstracted and whether the second H-abstraction to be abstracted in the final desaturation step locates in a suitable orientation. The highly reactive FeIV-oxo species prefers to abstract a hydrogen atom from one of two methyl groups in penN to trigger the ring arrangement. After the H-abstraction, the generated methylene radical intermediate can easily initiate the ring arrangement. First, the C-S bond cleaves to generate a thiyl radical, which is in concert with the formation of the terminal C═C double bond; the newly generated thiyl radical then rapidly shifts to the more stable tertiary C atom to complete ring expansion. In the final step, the FeIII-OH species abstracts the second hydrogen to give the desaturated DAOC product. During the catalysis, no active site residue is directly involved in the chemistry, which implies that the other pocket residues except the coordinate ones with iron play a role only in anchoring the substrate.
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Affiliation(s)
- Yaru Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Junyou Shi
- College of Chemistry and Environmental Science, Qujing Normal University, Qujing, Yunnan 655011, China
| | - Yongjun Liu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
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5
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Evaluation of a concerted vs. sequential oxygen activation mechanism in α-ketoglutarate-dependent nonheme ferrous enzymes. Proc Natl Acad Sci U S A 2020; 117:5152-5159. [PMID: 32094179 DOI: 10.1073/pnas.1922484117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Determining the requirements for efficient oxygen (O2) activation is key to understanding how enzymes maintain efficacy and mitigate unproductive, often detrimental reactivity. For the α-ketoglutarate (αKG)-dependent nonheme iron enzymes, both a concerted mechanism (both cofactor and substrate binding prior to reaction with O2) and a sequential mechanism (cofactor binding and reaction with O2 precede substrate binding) have been proposed. Deacetoxycephalosporin C synthase (DAOCS) is an αKG-dependent nonheme iron enzyme for which both of these mechanisms have been invoked to generate an intermediate that catalyzes oxidative ring expansion of penicillin substrates in cephalosporin biosynthesis. Spectroscopy shows that, in contrast to other αKG-dependent enzymes (which are six coordinate when only αKG is bound to the FeII), αKG binding to FeII-DAOCS results in ∼45% five-coordinate sites that selectively react with O2 relative to the remaining six-coordinate sites. However, this reaction produces an FeIII species that does not catalyze productive ring expansion. Alternatively, simultaneous αKG and substrate binding to FeII-DAOCS produces five-coordinate sites that rapidly react with O2 to form an FeIV=O intermediate that then reacts with substrate to produce cephalosporin product. These results demonstrate that the concerted mechanism is operative in DAOCS and by extension, other nonheme iron enzymes.
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6
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Rabe P, Kamps JJAG, Schofield CJ, Lohans CT. Roles of 2-oxoglutarate oxygenases and isopenicillin N synthase in β-lactam biosynthesis. Nat Prod Rep 2018; 35:735-756. [PMID: 29808887 PMCID: PMC6097109 DOI: 10.1039/c8np00002f] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Indexed: 01/01/2023]
Abstract
Covering: up to 2017 2-Oxoglutarate (2OG) dependent oxygenases and the homologous oxidase isopenicillin N synthase (IPNS) play crucial roles in the biosynthesis of β-lactam ring containing natural products. IPNS catalyses formation of the bicyclic penicillin nucleus from a tripeptide. 2OG oxygenases catalyse reactions that diversify the chemistry of β-lactams formed by both IPNS and non-oxidative enzymes. Reactions catalysed by the 2OG oxygenases of β-lactam biosynthesis not only involve their typical hydroxylation reactions, but also desaturation, epimerisation, rearrangement, and ring-forming reactions. Some of the enzymes involved in β-lactam biosynthesis exhibit remarkable substrate and product selectivities. We review the roles of 2OG oxygenases and IPNS in β-lactam biosynthesis, highlighting opportunities for application of knowledge of their roles, structures, and mechanisms.
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Affiliation(s)
- Patrick Rabe
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Jos J A G Kamps
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Christopher J Schofield
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Christopher T Lohans
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK.
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7
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Dunbar KL, Scharf DH, Litomska A, Hertweck C. Enzymatic Carbon-Sulfur Bond Formation in Natural Product Biosynthesis. Chem Rev 2017; 117:5521-5577. [PMID: 28418240 DOI: 10.1021/acs.chemrev.6b00697] [Citation(s) in RCA: 345] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sulfur plays a critical role for the development and maintenance of life on earth, which is reflected by the wealth of primary metabolites, macromolecules, and cofactors bearing this element. Whereas a large body of knowledge has existed for sulfur trafficking in primary metabolism, the secondary metabolism involving sulfur has long been neglected. Yet, diverse sulfur functionalities have a major impact on the biological activities of natural products. Recent research at the genetic, biochemical, and chemical levels has unearthed a broad range of enzymes, sulfur shuttles, and chemical mechanisms for generating carbon-sulfur bonds. This Review will give the first systematic overview on enzymes catalyzing the formation of organosulfur natural products.
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Affiliation(s)
- Kyle L Dunbar
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI) , Beutenbergstrasse 11a, 07745 Jena, Germany
| | - Daniel H Scharf
- Life Sciences Institute, University of Michigan , 210 Washtenaw Avenue, Ann Arbor, Michigan 48109-2216, United States
| | - Agnieszka Litomska
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI) , Beutenbergstrasse 11a, 07745 Jena, Germany
| | - Christian Hertweck
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI) , Beutenbergstrasse 11a, 07745 Jena, Germany.,Friedrich Schiller University , 07743 Jena, Germany
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8
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Kal S, Que L. Dioxygen activation by nonheme iron enzymes with the 2-His-1-carboxylate facial triad that generate high-valent oxoiron oxidants. J Biol Inorg Chem 2017; 22:339-365. [PMID: 28074299 DOI: 10.1007/s00775-016-1431-2] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/13/2016] [Indexed: 11/24/2022]
Abstract
The 2-His-1-carboxylate facial triad is a widely used scaffold to bind the iron center in mononuclear nonheme iron enzymes for activating dioxygen in a variety of oxidative transformations of metabolic significance. Since the 1990s, over a hundred different iron enzymes have been identified to use this platform. This structural motif consists of two histidines and the side chain carboxylate of an aspartate or a glutamate arranged in a facial array that binds iron(II) at the active site. This triad occupies one face of an iron-centered octahedron and makes the opposite face available for the coordination of O2 and, in many cases, substrate, allowing the tailoring of the iron-dioxygen chemistry to carry out a plethora of diverse reactions. Activated dioxygen-derived species involved in the enzyme mechanisms include iron(III)-superoxo, iron(III)-peroxo, and high-valent iron(IV)-oxo intermediates. In this article, we highlight the major crystallographic, spectroscopic, and mechanistic advances of the past 20 years that have significantly enhanced our understanding of the mechanisms of O2 activation and the key roles played by iron-based oxidants.
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Affiliation(s)
- Subhasree Kal
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lawrence Que
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA.
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9
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Abstract
The non-heme Fe enzymes are ubiquitous in nature and perform a wide range of functions involving O2 activation. These had been difficult to study relative to heme enzymes; however, spectroscopic methods that provide significant insight into the correlation of structure with function have now been developed. This Current Topics article summarizes both the molecular mechanism these enzymes use to control O2 activation in the presence of cosubstrates and the oxygen intermediates these reactions generate. Three types of O2 activation are observed. First, non-heme reactivity is shown to be different from heme chemistry where a low-spin FeIII-OOH non-heme intermediate directly reacts with substrate. Also, two subclasses of non-heme Fe enzymes generate high-spin FeIV═O intermediates that provide both σ and π frontier molecular orbitals that can control selectivity. Finally, for several subclasses of non-heme Fe enzymes, binding of the substrate to the FeII site leads to the one-electron reductive activation of O2 to an FeIII-superoxide capable of H atom abstraction and electrophilic attack.
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Affiliation(s)
- Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Serra Goudarzi
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Kyle D Sutherlin
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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10
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Proshlyakov DA, McCracken J, Hausinger RP. Spectroscopic analyses of 2-oxoglutarate-dependent oxygenases: TauD as a case study. J Biol Inorg Chem 2016; 22:367-379. [PMID: 27812832 DOI: 10.1007/s00775-016-1406-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 10/25/2016] [Indexed: 11/28/2022]
Abstract
A wide range of spectroscopic approaches have been used to interrogate the mononuclear iron metallocenter in 2-oxoglutarate (2OG)-dependent oxygenases. The results from these spectroscopic studies have provided valuable insights into the structural changes at the active site during substrate binding and catalysis, thus providing critical information that complements investigations of these enzymes by X-ray crystallography, biochemical, and computational approaches. This mini-review highlights taurine hydroxylase (taurine:2OG dioxygenase, TauD) as a case study to illustrate the wealth of knowledge that can be generated by applying a diverse array of spectroscopic investigations to a single enzyme. In particular, electronic absorption, circular dichroism, magnetic circular dichroism, conventional and pulse electron paramagnetic, Mössbauer, X-ray absorption, and resonance Raman methods have been exploited to uncover the properties of the metal site in TauD.
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Affiliation(s)
- Denis A Proshlyakov
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA
| | - John McCracken
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA
| | - Robert P Hausinger
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA. .,Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
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11
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Sutherlin KD, Liu LV, Lee YM, Kwak Y, Yoda Y, Saito M, Kurokuzu M, Kobayashi Y, Seto M, Que L, Nam W, Solomon EI. Nuclear Resonance Vibrational Spectroscopic Definition of Peroxy Intermediates in Nonheme Iron Sites. J Am Chem Soc 2016; 138:14294-14302. [PMID: 27726349 DOI: 10.1021/jacs.6b07227] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
FeIII-(hydro)peroxy intermediates have been isolated in two classes of mononuclear nonheme Fe enzymes that are important in bioremediation: the Rieske dioxygenases and the extradiol dioxygenases. The binding mode and protonation state of the peroxide moieties in these intermediates are not well-defined, due to a lack of vibrational structural data. Nuclear resonance vibrational spectroscopy (NRVS) is an important technique for obtaining vibrational information on these and other intermediates, as it is sensitive to all normal modes with Fe displacement. Here, we present the NRVS spectra of side-on FeIII-peroxy and end-on FeIII-hydroperoxy model complexes and assign these spectra using calibrated DFT calculations. We then use DFT calculations to define and understand the changes in the NRVS spectra that arise from protonation and from opening the Fe-O-O angle. This study identifies four spectroscopic handles that will enable definition of the binding mode and protonation state of FeIII-peroxy intermediates in mononuclear nonheme Fe enzymes. These structural differences are important in determining the frontier molecular orbitals available for reactivity.
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Affiliation(s)
- Kyle D Sutherlin
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Lei V Liu
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Yong-Min Lee
- Department of Bioinspired Science, Department of Chemistry and Nano Science, Center for Biomimetic Systems, Ewha Womans University , Seoul 120-750, Korea
| | - Yeonju Kwak
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | | | - Makina Saito
- Research Reactor Institute, Kyoto University , Osaka 590-0494, Japan
| | - Masayuki Kurokuzu
- Research Reactor Institute, Kyoto University , Osaka 590-0494, Japan
| | | | - Makoto Seto
- Research Reactor Institute, Kyoto University , Osaka 590-0494, Japan
| | - Lawrence Que
- Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Wonwoo Nam
- Department of Bioinspired Science, Department of Chemistry and Nano Science, Center for Biomimetic Systems, Ewha Womans University , Seoul 120-750, Korea
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
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12
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Modified Deacetylcephalosporin C Synthase for the Biotransformation of Semisynthetic Cephalosporins. Appl Environ Microbiol 2016; 82:3711-3720. [PMID: 27084018 DOI: 10.1128/aem.00174-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 04/06/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Deacetylcephalosporin C synthase (DACS), a 2-oxoglutarate-dependent oxygenase synthesized by Streptomyces clavuligerus, transforms an inert methyl group of deacetoxycephalosporin C (DAOC) into an active hydroxyl group of deacetylcephalosporin C (DAC) during the biosynthesis of cephalosporin. It is a step which is chemically difficult to accomplish, but its development by use of an enzymatic method with DACS can facilitate a cost-effective technology for the manufacture of semisynthetic cephalosporin intermediates such as 7-amino-cephalosporanic acid (7ACA) and hydroxymethyl-7-amino-cephalosporanic acid (HACA) from cephalosporin G. As the native enzyme showed negligible activity toward cephalosporin G, an unnatural and less expensive substrate analogue, directed-evolution strategies such as random, semirational, rational, and computational methods were used for systematic engineering of DACS for improved activity. In comparison to the native enzyme, several variants with improved catalytic efficiency were found. The enzyme was stable for several days and is expressed in soluble form at high levels with significantly higher kcat/Km values. The efficacy and industrial scalability of one of the selected variants, CefFGOS, were demonstrated in a process showing complete bioconversion of 18 g/liter of cephalosporin G into deacetylcephalosporin G (DAG) in about 80 min and showed reproducible results at higher substrate concentrations as well. DAG could be converted completely into HACA in about 30 min by a subsequent reaction, thus facilitating scalability toward commercialization. The experimental findings with several mutants were also used to rationalize the functional conformation deduced from homology modeling, and this led to the disclosure of critical regions involved in the catalysis of DACS. IMPORTANCE 7ACA and HACA serve as core intermediates for the manufacture of several semisynthetic cephalosporins. As they are expensive, a cost-effective enzyme technology for the manufacture of these intermediates is required. Deacetylcephalosporin C synthase (DACS) was identified as a candidate enzyme for the development of technology from cephalosporin G in this study. Directed-evolution strategies were employed to enhance the catalytic efficiency of deacetylcephalosporin C synthase. One of the selected mutants of deacetylcephalosporin C synthase could convert high concentrations of cephalosporin G into DAG, which subsequently could be converted into HACA completely. As cephalosporin G is inexpensive and readily available, the technology would lead to a substantial reduction in the cost for these intermediates upon commercialization.
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13
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The different catalytic roles of the metal-binding ligands in human 4-hydroxyphenylpyruvate dioxygenase. Biochem J 2016; 473:1179-89. [PMID: 26936969 DOI: 10.1042/bcj20160146] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/02/2016] [Indexed: 11/17/2022]
Abstract
4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a non-haem iron(II)-dependent oxygenase that catalyses the conversion of 4-hydroxyphenylpyruvate (HPP) to homogentisate (HG). In the active site, a strictly conserved 2-His-1-Glu facial triad co-ordinates the iron ready for catalysis. Substitution of these residues resulted in about a 10-fold decrease in the metal binding affinity, as measured by isothermal titration calorimetry, and a large reduction in enzyme catalytic efficiencies. The present study revealed the vital role of the ligand Glu(349) in enzyme function. Replacing this residue with alanine resulted in loss of activity. The E349G variant retained 5% activity for the coupled reaction, suggesting that co-ordinating water may be able to support activation of the trans-bound dioxygen upon substrate binding. The reaction catalysed by the H183A variant was fully uncoupled. H183A variant catalytic activity resulted in protein cleavage between Ile(267) and Ala(268) and the production of an N-terminal fragment. The H266A variant was able to produce 4-hydroxyphenylacetate (HPA), demonstrating that decarboxylation had occurred but that there was no subsequent product formation. Structural modelling of the variant enzyme with bound dioxygen revealed the rearrangement of the co-ordination environment and the dynamic behaviour of bound dioxygen in the H266A and H183A variants respectively. These models suggest that the residues regulate the geometry of the reactive oxygen intermediate during the oxidation reaction. The mutagenesis and structural simulation studies demonstrate the critical and unique role of each ligand in the function of HPPD, and which correlates with their respective co-ordination position.
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14
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Abstract
Mononuclear non-heme Fe(II)- and 2-oxoglutarate (2OG)-dependent oxygenases comprise a large family of enzymes that utilize an Fe(IV)-oxo intermediate to initiate diverse oxidative transformations with important biological roles. Here, four of the major types of Fe(II)/2OG-dependent reactions are detailed: hydroxylation, halogenation, ring formation, and desaturation. In addition, an atypical epimerization reaction is described. Studies identifying several key intermediates in catalysis are concisely summarized, and the proposed mechanisms are explained. In addition, a variety of other transformations catalyzed by selected family members are briefly described to further highlight the chemical versatility of these enzymes.
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Affiliation(s)
- Salette Martinez
- Departments of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824
| | - Robert P Hausinger
- Departments of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824; Departments of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824.
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15
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Structural Insights into Substrate Specificity of Feruloyl-CoA 6'-Hydroxylase from Arabidopsis thaliana. Sci Rep 2015; 5:10355. [PMID: 25993561 PMCID: PMC4438608 DOI: 10.1038/srep10355] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 04/09/2015] [Indexed: 01/13/2023] Open
Abstract
Coumarins belong to an important class of plant secondary metabolites. Feruloyl-CoA 6’-hydroxylase (F6’H), a 2-oxoglutarate dependent dioxygenase (2OGD), catalyzes a pivotal step in the biosynthesis of a simple coumarin scopoletin. In this study, we determined the 3-dimensional structure of the F6’H1 apo enzyme by X-ray crystallography. It is the first reported structure of a 2OGD enzyme involved in coumarin biosynthesis and closely resembles the structure of Arabidopsis thaliana anthocyanidin synthase. To better understand the mechanism of enzyme catalysis and substrate specificity, we also generated a homology model of a related ortho-hydroxylase (C2’H) from sweet potato. By comparing these two structures, we targeted two amino acid residues and verified their roles in substrate binding and specificity by site-directed mutagenesis.
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16
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Andersson I, Valegård K. 2-Oxoglutarate-Dependent Oxygenases of Cephalosporin Synthesis. 2-OXOGLUTARATE-DEPENDENT OXYGENASES 2015. [DOI: 10.1039/9781782621959-00385] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Central steps in the biosynthetic pathways of some of the most commonly used antibiotics, the cephalosporins, are catalysed by 2-oxoglutarate (2OG)-dependent oxygenases. Deacetoxycephalosporin C synthase (DAOCS) catalyses the 2OG-dependent oxidative expansion of the five-membered thiazolidine ring of the penicillin nucleus into the six-membered dihydrothiazine ring of the cephalosporin nucleus. DAOCS uses dioxygen to create a reactive iron–oxygen intermediate from ferrous ion to drive the reaction. In prokaryotic cephalosporin producers, the cephalosporin product, DAOC, is hydroxylated at the 3′-position to form deacetylcephalosporin C (DAC) as catalysed by a second 2OG-dependent enzyme, DAC synthase (DACS). In eukaryotic cephalosporin producers, the reaction is catalysed by a bifunctional enzyme, DAOC/DACS, that catalyses both the ring expansion and the 3′-hydroxylation reactions. The prokaryotic and eukaryotic enzymes are closely related to DAOCS by sequence, suggesting these enzymes may have evolved by gene duplication. Cephamycin C-producing microorganisms use two enzymes, encoded by the genes cmcI/J, to convert cephalosporins to their 7α-methoxy derivatives that are less vulnerable to β-lactam hydrolysing enzymes. The methoxylation reaction is dependent on Fe(ii), 2OG and S-adenosylmethionine, suggesting the involvement of another 2OG-dependent oxygenase. Herein, structural and mechanistic features are summarized for these 2OG enzymes that utilize this common and flexible mode of dioxygen activation.
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Affiliation(s)
- Inger Andersson
- Department of Cell and Molecular Biology, Uppsala University Box 596, S-751 24 Uppsala Sweden
| | - Karin Valegård
- Department of Cell and Molecular Biology, Uppsala University Box 596, S-751 24 Uppsala Sweden
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Tarhonskaya H, Szöllössi A, Leung IKH, Bush JT, Henry L, Chowdhury R, Iqbal A, Claridge TDW, Schofield CJ, Flashman E. Studies on Deacetoxycephalosporin C Synthase Support a Consensus Mechanism for 2-Oxoglutarate Dependent Oxygenases. Biochemistry 2014; 53:2483-93. [DOI: 10.1021/bi500086p] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Hanna Tarhonskaya
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Andrea Szöllössi
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Ivanhoe K. H. Leung
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Jacob T. Bush
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Luc Henry
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Rasheduzzaman Chowdhury
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Aman Iqbal
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Timothy D. W. Claridge
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Christopher J. Schofield
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Emily Flashman
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
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18
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Blomberg MRA, Borowski T, Himo F, Liao RZ, Siegbahn PEM. Quantum chemical studies of mechanisms for metalloenzymes. Chem Rev 2014; 114:3601-58. [PMID: 24410477 DOI: 10.1021/cr400388t] [Citation(s) in RCA: 431] [Impact Index Per Article: 43.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Margareta R A Blomberg
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden
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19
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Recent advances in the biosynthesis of penicillins, cephalosporins and clavams and its regulation. Biotechnol Adv 2013; 31:287-311. [DOI: 10.1016/j.biotechadv.2012.12.001] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 11/30/2012] [Accepted: 12/01/2012] [Indexed: 11/23/2022]
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20
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Hamed RB, Gomez-Castellanos JR, Henry L, Ducho C, McDonough MA, Schofield CJ. The enzymes of β-lactam biosynthesis. Nat Prod Rep 2013; 30:21-107. [DOI: 10.1039/c2np20065a] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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21
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Structural Insight into the Prolyl Hydroxylase PHD2: A Molecular Dynamics and DFT Study. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201200391] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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22
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Li T, Huo L, Pulley C, Liu A. Decarboxylation mechanisms in biological system. Bioorg Chem 2012; 43:2-14. [PMID: 22534166 DOI: 10.1016/j.bioorg.2012.03.001] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Revised: 03/04/2012] [Accepted: 03/19/2012] [Indexed: 11/30/2022]
Abstract
This review examines the mechanisms propelling cofactor-independent, organic cofactor-dependent and metal-dependent decarboxylase chemistry. Decarboxylation, the removal of carbon dioxide from organic acids, is a fundamentally important reaction in biology. Numerous decarboxylase enzymes serve as key components of aerobic and anaerobic carbohydrate metabolism and amino acid conversion. In the past decade, our knowledge of the mechanisms enabling these crucial decarboxylase reactions has continued to expand and inspire. This review focuses on the organic cofactors biotin, flavin, NAD, pyridoxal 5'-phosphate, pyruvoyl, and thiamin pyrophosphate as catalytic centers. Significant attention is also placed on the metal-dependent decarboxylase mechanisms.
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Affiliation(s)
- Tingfeng Li
- Department of Biochemistry, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA
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23
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Farquhar ER, Emerson JP, Koehntop KD, Reynolds MF, Trmčić M, Que L. In vivo self-hydroxylation of an iron-substituted manganese-dependent extradiol cleaving catechol dioxygenase. J Biol Inorg Chem 2011; 16:589-97. [PMID: 21279661 DOI: 10.1007/s00775-011-0760-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Accepted: 01/16/2011] [Indexed: 11/30/2022]
Abstract
The homoprotocatechuate 2,3-dioxygenase from Arthrobacter globiformis (MndD) catalyzes the oxidative ring cleavage reaction of its catechol substrate in an extradiol fashion. Although this reactivity is more typically associated with non-heme iron enzymes, MndD exhibits an unusual specificity for manganese(II). MndD is structurally very similar to the iron(II)-dependent homoprotocatechuate 2,3-dioxygenase from Brevibacterium fuscum (HPCD), and we have previously shown that both MndD and HPCD are equally active towards substrate turnover with either iron(II) or manganese(II) (Emerson et al. in Proc. Natl. Acad. Sci. USA 105:7347-7352, 2008). However, expression of MndD in Escherichia coli under aerobic conditions in the presence of excess iron results in the isolation of inactive blue-green iron-substituted MndD. Spectroscopic studies indicate that this form of iron-substituted MndD contains an iron(III) center with a bound catecholate, which is presumably generated by in vivo self-hydroxylation of a second-sphere tyrosine residue, as found for other self-hydroxylated non-heme iron oxygenases. The absence of this modification in either the native manganese-containing MndD or iron-containing HPCD suggests that the metal center of iron-substituted MndD is able to bind and activate O(2) in the absence of its substrate, employing a high-valence oxoiron oxidant to carry out the observed self-hydroxylation chemistry. These results demonstrate that the active site metal in MndD can support two dramatically different O(2) activation pathways, further highlighting the catalytic flexibility of enzymes containing a 2-His-1-carboxylate facial triad metal binding motif.
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Affiliation(s)
- Erik R Farquhar
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455, USA
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24
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Wu XB, Tian XY, Ji JJ, Wu WB, Fan KQ, Yang KQ. Saturation mutagenesis of Acremonium chrysogenum deacetoxy/deacetylcephalosporin C synthase R308 site confirms its role in controlling substrate specificity. Biotechnol Lett 2010; 33:805-12. [DOI: 10.1007/s10529-010-0504-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 12/08/2010] [Indexed: 11/27/2022]
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Chapter 16. Enzymology of beta-lactam compounds with cephem structure produced by actinomycete. Methods Enzymol 2009; 458:401-29. [PMID: 19374992 DOI: 10.1016/s0076-6879(09)04816-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Cephamycins are beta-lactam antibiotics with a cephem structure produced by actinomycetes. They are synthesized by a pathway similar to that of cephalosporin C in filamentous fungi but the actinomycetes pathway contains additional enzymes for the formation of the alpha-aminoadipic acid (AAA) precursor and for the final steps specific to cephemycins. Most of the biochemical and genetic studies on cephemycins have been made on cephemycin C biosynthesis in the producer strains Streptomyces clavuligerus ATCC27064 and Amycolatopsis lactamdurans NRRL3802. Genes encoding cephamycin C biosynthetic enzymes are clustered in both actinomycetes. Ten enzymatic steps are involved in the formation of cephamycin C. The precursor alpha-AAA is formed by the sequential action of lysine-6-aminotransferase and piperideine-6-carboxylate dehydrogenase. Steps common to cephalosporin C biosynthesis include the formation of the tripeptide L-delta-alpha-aminoadipyl-L-cysteinyl-D-valine (ACV) by ACV synthetase, the cyclization of ACV to form isopenicillin N (IPN) by IPN synthase, the epimerization of IPN to penicillin N by isopenicillin N epimerase, the ring expansion of penicillin N to a six member cephem ring by deacetoxycephalosporin C synthase (DAOCS) and the hydroxylation at C-3' by deacetylcephalosporin C hydroxylase. However, in actinomycetes, the epimerization step is different from that in cephalosporin-producing fungi, and the expansion of the ring and its hydroxylation are performed by separate enzymes. Specific steps in cephamycin biosynthesis include the carbamoylation at C-3' by cephem carbamoyl transferase and the introduction of a methoxyl group at C-7 by the joint action of a C-7 cephem-hydroxylase and a methyltransferase. All the enzymes of the pathway have been purified almost to homogeneity and the DAOC synthase and 7-hydroxycephem-methyltransferase (CmcI) of S. clavuligerus have been crystallized giving insights into the mode of action of these enzymes. The cefE gene of S. clavuligerus, encoding DAOCS, has been extensively used to expand the penicillin ring in filamentous fungi in vivo using DNA recombinant technology.
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Directed evolution and rational approaches to improving Streptomyces clavuligerus deacetoxycephalosporin C synthase for cephalosporin production. J Ind Microbiol Biotechnol 2009; 36:619-33. [DOI: 10.1007/s10295-009-0549-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 02/12/2009] [Indexed: 10/21/2022]
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Sim Goo K, Song Chua C, Sim TS. A complete library of amino acid alterations at R306 in Streptomyces clavuligerus deacetoxycephalosporin C synthase demonstrates its structural role in the ring-expansion activity. Proteins 2008; 70:739-47. [PMID: 17729280 DOI: 10.1002/prot.21549] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In a previous study, the conserved arginine residue at position 306 of Streptomyces clavuligerus deacetoxycephalsoporin C synthase (scDAOCS), when mutated to leucine, resulted in 191% increase in converting ampicillin to its expanded cephalosporin moiety compared with that of the wild-type enzyme. However, the role of this residue in eliciting the improved enzymatic activity is not well understood. In this study, probing the molecular basis of amino acid substitutions at position 306 has underscored its importance for engineering various improvements in the ring expansion activity. Structural modeling using SwissPdbViewer revealed that R306 is surrounded by a hydrophobic cleft formed by residues Y184, L186, W297, I298, and V303. Hence, the improved activity achieved by the R306L mutation was probably because of better hydrophobic packing in this region. To evaluate the role of amino acids at position 306 of scDAOCS and its influence on the molecular status of the enzyme at this locality, alteration to 18 other amino acids was done by site-directed mutagenesis. The effects of each substitution on the enzyme activity were determined by bioassay using penicillin substrates: ampicillin, penicillin G, phenethicillin, and carbenicillin. Results obtained showed a drastic reduction in enzyme activity when R306 was replaced with charged or polar residues, thus emphasizing the importance of hydrophobic packing around this site. The bioassay results also illustrated that apart from leucine, substitutions to nonpolar residues, isoleucine and methionine, were able to improve the ampicillin conversion activity of scDAOCS by 168 and 113% of the wild-type enzyme activity, respectively. Similar trend of effects from each mutation was also observed for penicillin G, phenethicillin, and carbenicillin conversions. The enhanced enzyme activities were supported by spectrophotometric assay indicating that all these mutants have lower K(m) values (R306L: 1.09 mM; R306I: 2.64 mM; R306M: 5.68 mM) than the wild-type enzyme (8.33 mM), resulting in improvement in the enzyme's substrate binding affinity. Hence, this mutational study of amino acids situated at 306 of scDAOCS has provided a better understanding of the significance of specific amino acid residues at this position which can improve its ring-expansion activity when given a plethora of beta-lactam substrates to generate corresponding, possibly new, cephalosporins.
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Affiliation(s)
- Kian Sim Goo
- Department of Microbiology, Yong Loo Lin School of Medicine, Singapore 117597
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28
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Brownlee J, He P, Moran GR, Harrison DHT. Two Roads Diverged: The Structure of Hydroxymandelate Synthase from Amycolatopsis orientalis in Complex with 4-Hydroxymandelate,. Biochemistry 2008; 47:2002-13. [DOI: 10.1021/bi701438r] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- June Brownlee
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, Illinois 60064, and Department of Chemistry and Biochemistry, University of WisconsinMilwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211-3029
| | - Panqing He
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, Illinois 60064, and Department of Chemistry and Biochemistry, University of WisconsinMilwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211-3029
| | - Graham R. Moran
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, Illinois 60064, and Department of Chemistry and Biochemistry, University of WisconsinMilwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211-3029
| | - David H. T. Harrison
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, Illinois 60064, and Department of Chemistry and Biochemistry, University of WisconsinMilwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211-3029
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29
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Relevant double mutations in bioengineered Streptomyces clavuligerus deacetoxycephalosporin C synthase result in higher binding specificities which improve penicillin bioconversion. Appl Environ Microbiol 2007; 74:1167-75. [PMID: 18083859 DOI: 10.1128/aem.02230-07] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptomyces clavuligerus deacetoxycephalosporin C synthase (ScDAOCS) is an important industrial enzyme for the production of 7-aminodeacetoxycephalosporanic acid, which is a precursor for cephalosporin synthesis. Single mutations of six amino acid residues, V275, C281, N304, I305, R306, and R307, were previously shown to result in enhanced levels of ampicillin conversion, with activities ranging from 129 to 346% of the wild-type activity. In this study, these mutations were paired to investigate their effects on enzyme catalysis. The bioassay results showed that the C-terminal mutations (N304X [where X is alanine, leucine, methionine, lysine, or arginine], I305M, R306L, and R307L) in combination with C281Y substantially increased the conversion of ampicillin; the activity was up to 491% of the wild-type activity. Similar improvements were observed for converting carbenicillin (up to 1,347% of the wild-type activity) and phenethicillin (up to 1,109% of the wild-type activity). Interestingly, the N304X R306L double mutants exhibited lower activities for penicillin G conversion, and activities that were 40 to 114% of wild-type enzyme activity were detected. Based on kinetic studies using ampicillin, it was clear that the increases in the activities of the double mutants relative to those of the corresponding single mutants were due to enhanced substrate binding affinities. These results also validated the finding that the N304R and I305M mutations are ideal for increasing the substrate binding affinity and turnover rate of the enzyme, respectively. This study provided further insight into the structure-function interaction of ScDAOCS with different penicillin substrates, thus providing a useful platform for further rational modification of its enzymatic properties.
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Flashman E, Bagg EAL, Chowdhury R, Mecinović J, Loenarz C, McDonough MA, Hewitson KS, Schofield CJ. Kinetic rationale for selectivity toward N- and C-terminal oxygen-dependent degradation domain substrates mediated by a loop region of hypoxia-inducible factor prolyl hydroxylases. J Biol Chem 2007; 283:3808-15. [PMID: 18063574 DOI: 10.1074/jbc.m707411200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hydroxylation of two conserved prolyl residues in the N- and C-terminal oxygen-dependent degradation domains (NODD and CODD) of the alpha-subunit of hypoxia-inducible factor (HIF) signals for its degradation via the ubiquitin-proteasome pathway. In human cells, three prolyl hydroxylases (PHDs 1-3) belonging to the Fe(II) and 2-oxoglutarate (2OG)-dependent oxygenase family catalyze prolyl hydroxylation with differing selectivity for CODD and NODD. Sequence analysis of the catalytic domains of the PHDs in the light of crystal structures for PHD2, and results for other 2OG oxygenases, suggested that either the C-terminal region or a loop linking two beta-strands (beta2 and beta3 in human PHD2) are important in determining substrate selectivity. Mutation analyses on PHD2 revealed that the beta2beta3 loop is a major determinant in conferring selectivity for CODD over NODD peptides. A chimeric PHD in which the beta2beta3 loop of PHD2 was replaced with that of PHD3 displayed an almost complete selectivity for CODD (in competition experiments), as observed for wild-type PHD3. CODD was observed to bind much more tightly to this chimeric protein than the wild type PHD2 catalytic domain.
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Affiliation(s)
- Emily Flashman
- Chemistry Research Laboratory, Department of Chemistry and the Oxford Centre for Integrative Systems Biology, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
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Koski MK, Hieta R, Böllner C, Kivirikko KI, Myllyharju J, Wierenga RK. The Active Site of an Algal Prolyl 4-Hydroxylase Has a Large Structural Plasticity. J Biol Chem 2007; 282:37112-23. [DOI: 10.1074/jbc.m706554200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Abstract
High-valent non-heme iron-oxo intermediates have been proposed for decades as the key intermediates in numerous biological oxidation reactions. In the past three years, the first direct characterization of such intermediates has been provided by studies of several alphaKG-dependent oxygenases that catalyze either hydroxylation or halogenation of their substrates. In each case, the Fe(IV)-oxo intermediate is implicated in cleavage of the aliphatic C-H bond to initiate hydroxylation or halogenation. The observation of non-heme Fe(IV)-oxo intermediates and Fe(II)-containing product(s) complexes with almost identical spectroscopic parameters in the reactions of two distantly related alphaKG-dependent hydroxylases suggests that members of this subfamily follow a conserved mechanism for substrate hydroxylation. In contrast, for the alphaKG-dependent non-heme iron halogenase, CytC3, two distinct Fe(IV) complexes form and decay together, suggesting that they are in rapid equilibrium. The existence of two distinct conformers of the Fe site may be the key factor accounting for the divergence of the halogenase reaction from the more usual hydroxylation pathway after C-H bond cleavage. Distinct transformations catalyzed by other mononuclear non-heme enzymes are likely also to involve initial C-H bond cleavage by Fe(IV)-oxo complexes, followed by diverging reactivities of the resulting Fe(III)-hydroxo/substrate radical intermediates.
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Affiliation(s)
- Carsten Krebs
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | | | - Christopher T. Walsh
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - J. Martin Bollinger
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
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Gebhardt YH, Witte S, Steuber H, Matern U, Martens S. Evolution of flavone synthase I from parsley flavanone 3beta-hydroxylase by site-directed mutagenesis. PLANT PHYSIOLOGY 2007; 144:1442-54. [PMID: 17535823 PMCID: PMC1914147 DOI: 10.1104/pp.107.098392] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Flavanone 3beta-hydroxylase (FHT) and flavone synthase I (FNS I) are 2-oxoglutarate-dependent dioxygenases with 80% sequence identity, which catalyze distinct reactions in flavonoid biosynthesis. However, FNS I has been reported exclusively from a few Apiaceae species, whereas FHTs are more abundant. Domain-swapping experiments joining the N terminus of parsley (Petroselinum crispum) FHT with the C terminus of parsley FNS I and vice versa revealed that the C-terminal portion is not essential for FNS I activity. Sequence alignments identified 26 amino acid substitutions conserved in FHT versus FNS I genes. Homology modeling, based on the related anthocyanidin synthase structure, assigned seven of these amino acids (FHT/FNS I, M106T, I115T, V116I, I131F, D195E, V200I, L215V, and K216R) to the active site. Accordingly, FHT was modified by site-directed mutagenesis, creating mutants encoding from one to seven substitutions, which were expressed in yeast (Saccharomyces cerevisiae) for FNS I and FHT assays. The exchange I131F in combination with either M106T and D195E or L215V and K216R replacements was sufficient to confer some FNS I side activity. Introduction of all seven FNS I substitutions into the FHT sequence, however, caused a nearly complete change in enzyme activity from FHT to FNS I. Both FHT and FNS I were proposed to initially withdraw the beta-face-configured hydrogen from carbon-3 of the naringenin substrate. Our results suggest that the 7-fold substitution affects the orientation of the substrate in the active-site pocket such that this is followed by syn-elimination of hydrogen from carbon-2 (FNS I reaction) rather than the rebound hydroxylation of carbon-3 (FHT reaction).
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Affiliation(s)
- Yvonne Helen Gebhardt
- Institut für Pharmazeutische Biologie , Philipps-Universität Marburg, Marburg, Germany
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White HD, Ashcroft AE. Real-time measurement of myosin-nucleotide noncovalent complexes by electrospray ionization mass spectrometry. Biophys J 2007; 93:914-9. [PMID: 17483158 PMCID: PMC1913167 DOI: 10.1529/biophysj.106.101618] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nanoelectrospray ionization mass spectrometry has been used to measure the binding of ATP and ADP to the active site of rabbit skeletal myosin-S1. Increases in the molecular mass of myosin-S1 of 425 +/- 10 Da were obtained with the binding of ADP to the active site and by 530 +/- 10 Da with either ATP or hydrolysis products ADP and phosphate. Active site titrations of myosin-S1 with ADP gave a stoichiometry of approximately 1 ADP/S1 with an affinity in the micromolar range. The binding of ATP to myosin-S1 could be observed in the presence of up to 60 muM of excess MgATP without nonspecific binding of MgATP to the myosin. Conversion of the nucleotide complex containing an equilibrium mixture of ATP and ADP-Pi bound to myosin-S1 to one containing only bound ADP occurs at a rate consistent with that of the known steady-state rate of ATP hydrolysis. We expect this method to be of considerable use in the analysis of ligand binding and hydrolysis by the active sites of expressed myosin and myosin subfragments, which are not available in sufficient quantities for conventional methods of measurement of ligand binding.
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Affiliation(s)
- Howard D White
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia 23507, USA.
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Purpero V, Moran GR. The diverse and pervasive chemistries of the alpha-keto acid dependent enzymes. J Biol Inorg Chem 2007; 12:587-601. [PMID: 17431691 DOI: 10.1007/s00775-007-0231-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 03/15/2007] [Indexed: 12/01/2022]
Abstract
The number of identified and confirmed alpha-keto acid dependent oxygenases is increasing rapidly. All of these enzymes have a relatively simple liganding arrangement for a single ferrous ion but collectively conduct a highly diverse set of chemistries. While hydroxylations and a variety of oxidation reactions have been most commonly observed, new reactions involving dealkylations, epimerizations and halogenations have recently been discovered. In this minireview we present what is known of the alpha-keto acid dependent enzymes and offer an argument that the chemistry that is unique to each enzyme occurs only after the production of a pivotal ferryl-oxo intermediate.
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Affiliation(s)
- Vincent Purpero
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA
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Abstract
The adaptation of animals to oxygen availability is mediated by a transcription factor termed hypoxia-inducible factor (HIF). HIF is an alpha (alpha)/beta (beta) heterodimer that binds hypoxia response elements (HREs) of target genes, including some of medicinal importance, such as erythropoietin (EPO) and vascular endothelial growth factor (VEGF). While the concentration of the HIF-beta subunit, a constitutive nuclear protein, does not vary with oxygen availability, the abundance and activity of the HIF-alpha subunits are tightly regulated via oxygen-dependent modification of specific residues. Hydroxylation of prolyl residues (Pro402 and Pro564 in HIF-1alpha) promotes interaction with the von Hippel-Lindau E3 ubiquitin ligase and, consequently, proteolytic destruction by the ubiquitin-proteasome pathway. This prolyl hydroxylation is catalyzed by the prolyl-hydroxylase domain (PHD) containing enzymes for which three isozymes have been identified in humans (1-3). Additionally, asparaginyl hydroxylation (Asn803 in HIF-1alpha) by factor-inhibiting HIF (FIH) ablates interaction of the HIF-alpha subunit with the coactivator p300, providing an alternative mechanism for down-regulation of HIF-dependent genes. Under hypoxic conditions, when oxygen-mediated regulation of the alpha-subunits is curtailed or minimized, dimerization of the alpha- and beta-subunits occurs with subsequent target gene upregulation. Therapeutic activation of HIF signaling has been suggested as a potential treatment for numerous conditions, including ischemia, stroke, heart attack, inflammation, and wounding. One possible route to achieve this is via inhibition of the HIF hydroxylases. This chapter details methods for the purification and assaying of PHD2, the most abundant PHD and the most important in setting steady-state levels of HIF-alpha. Assays are described that measure the activity of PHD2 via direct and indirect means. Furthermore, conditions for the screening of small molecules against PHD2 are described.
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37
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Stok JE, Baldwin JE. Development of enzyme-linked immunosorbent assays for the detection of deacetoxycephalosporin C and isopenicillin N synthase activity. Anal Chim Acta 2006; 577:153-62. [PMID: 17723666 DOI: 10.1016/j.aca.2006.06.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Revised: 06/13/2006] [Accepted: 06/16/2006] [Indexed: 10/24/2022]
Abstract
Although there are a number of existing assays for monitoring the activity of both isopenicillin N synthase (IPNS) and deacetoxycephalosporin C synthase (DAOCS), none have demonstrated the qualities required for screening a mutant library. Hence, enzyme-linked immunosorbent assays (ELISAs) for IPNS and DAOCS were developed based on the detection of the catalytic turnover products isopenicillin N and cephalexin/phenylacetyl-7-aminodeacetoxycephalosporanic acid (G-7-ADCA), respectively. These assays are relatively fast compared to existing assays, such as the hole-plate bioassay, and are amenable with high-throughput screening. Both the IPNS and DAOCS-ELISAs were optimised for use with crude protein extracts rather than purified protein, thereby eliminating any additional time required for purification. The ELISA developed for the detection of cephalexin had an IC50 value of 154+/-9 ng mL(-1) and LOD of 7.2+/-2.2 ng mL(-1) under conditions required for the assay. Good recoveries and correlation was observed for spiked samples when the concentration of crude protein was kept below 1 mg mL(-1). The DAOCS-ELISA was found to have increased sensitivity compared to the hole-plate bioassay (10.3 microg mL(-1)). The IPNS-ELISA did not significantly increase the sensitivity (approximately 5 microg mL(-1)) compared to that of the hole-plate bioassay (16 microg mL(-1)) for isopenicillin N. The minimum amount of crude protein extract required for producing detectable amounts of product for both assays was below 0.5% of the maximum amount of protein that the assay could contain without any effect on the ELISA. This suggests that when screening a mutant library, mutants producing low amounts of the product could still be detected using these assays.
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Affiliation(s)
- Jeanette E Stok
- Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.
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38
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Clifton IJ, McDonough MA, Ehrismann D, Kershaw NJ, Granatino N, Schofield CJ. Structural studies on 2-oxoglutarate oxygenases and related double-stranded β-helix fold proteins. J Inorg Biochem 2006; 100:644-69. [PMID: 16513174 DOI: 10.1016/j.jinorgbio.2006.01.024] [Citation(s) in RCA: 339] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Revised: 01/12/2006] [Accepted: 01/12/2006] [Indexed: 01/09/2023]
Abstract
Mononuclear non-heme ferrous iron dependent oxygenases and oxidases constitute an extended enzyme family that catalyze a wide range of oxidation reactions. The largest known sub-group employs 2-oxoglutarate as a cosubstrate and catalysis by these and closely related enzymes is proposed to proceed via a ferryl intermediate coordinated to the active site via a conserved HXD/E...H motif. Crystallographic studies on the 2-oxoglutarate oxygenases and related enzymes have revealed a common double-stranded beta-helix core fold that supports the residues coordinating the iron. This fold is common to proteins of the cupin and the JmjC transcription factor families. The crystallographic studies on 2-oxoglutarate oxygenases and closely related enzymes are reviewed and compared with other metallo-enzymes/related proteins containing a double-stranded beta-helix fold. Proposals regarding the suitability of the active sites and folds of the 2-oxoglutarate oxygenases to catalyze reactions involving reactive oxidizing species are described.
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Affiliation(s)
- Ian J Clifton
- The Oxford Centre for Molecular Sciences and the Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, Oxon OX1 3TA, UK
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39
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Wei CL, Yang YB, Deng CH, Liu WC, Hsu JS, Lin YC, Liaw SH, Tsai YC. Directed evolution of Streptomyces clavuligerus deacetoxycephalosporin C synthase for enhancement of penicillin G expansion. Appl Environ Microbiol 2006; 71:8873-80. [PMID: 16332884 PMCID: PMC1317366 DOI: 10.1128/aem.71.12.8873-8880.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The deacetoxycephalosporin C synthase from Streptomyces clavuligerus was directly modified for enhancement of penicillin G expansion into phenylacetyl-7-aminodeacetoxycephalosporanic acid, an important intermediate in the industrial manufacture of cephalosporin antibiotics. Nine new mutants, mutants M73T, T91A, A106T, C155Y, Y184H, M188V, M188I, H244Q, and L277Q with 1.4- to 5.7-fold increases in the kcat/Km ratio, were obtained by screening 6,364 clones after error-prone PCR-based random mutagenesis. Subsequently, DNA shuffling was carried out to screen possible combinations of substitutions, including previous point mutations. One quaternary mutant, the C155Y/Y184H/V275I/C281Y mutant, which had a kcat/Km ratio that was 41-fold higher was found after 10,572 clones were assayed. The distinct mutants obtained using different mutagenesis methods demonstrated the complementarity of the techniques. Interestingly, most of the mutated residues that result in enhanced activities are located within or near the unique small barrel subdomain, suggesting that manipulation of this subdomain may be a constructive strategy for improvement of penicillin expansion. Several mutations had very distinct effects on expansion of penicillins N and G, perhaps due to different penicillin-interacting modes within the enzyme. Thus, the present study provided not only promising enzymes for cephalosporin biosynthesis but also a large number of mutants, which provided new insights into the structure-function relationship of the protein that should lead to further rational engineering.
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Affiliation(s)
- Chia-Li Wei
- Institute of Biochemistry, National Yang-Ming University, 155, Sec. 2, Li-Nong St., Pei-Tou, Taipei 11221, Taiwan
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40
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Wu XB, Fan KQ, Wang QH, Yang KQ. C-terminus mutations of Acremonium chrysogenum deacetoxy/deacetylcephalosporin C synthase with improved activity toward penicillin analogs. FEMS Microbiol Lett 2005; 246:103-10. [PMID: 15869968 DOI: 10.1016/j.femsle.2005.03.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Revised: 03/16/2005] [Accepted: 03/26/2005] [Indexed: 10/25/2022] Open
Abstract
Deacetoxy/deacetylcephalosporin C synthase (acDAOC/DACS) from Acremonium chrysogenum is a bifunctional enzyme that catalyzes both the ring-expansion of penicillin N to deacetoxycephalosporin C (DAOC) and the hydroxylation of the latter to deacetylcephalosporin C (DAC). Three residues N305, R307 and R308 located in close proximity to the C-terminus of acDAOC/DACS were each mutated to leucine. The N305L and R308L mutant acDAOC/DACSs showed significant improvement in their ability to convert penicillin analogs. R308 was identified for the first time as a critical residue for DAOC/DACS activity. Kinetic analyses of purified R308L enzyme indicated its improved catalytic efficiency is due to combined improvements of K(m) and k(cat). Comparative modeling of acDAOC/DACS supports the involvement of R308 in the formation of substrate-binding pocket.
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Affiliation(s)
- Xiao-Bin Wu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100080, PR China
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41
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Welford RWD, Clifton IJ, Turnbull JJ, Wilson SC, Schofield CJ. Structural and mechanistic studies on anthocyanidin synthase catalysed oxidation of flavanone substrates: the effect of C-2 stereochemistry on product selectivity and mechanism. Org Biomol Chem 2005; 3:3117-26. [PMID: 16106293 DOI: 10.1039/b507153d] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
During the biosynthesis of the tricyclic flavonoid natural products in plants, oxidative modifications to the central C-ring are catalysed by Fe(ii) and 2-oxoglutarate dependent oxygenases. The reactions catalysed by three of these enzymes; flavone synthase I, flavonol synthase and anthocyanidin synthase (ANS), are formally desaturations. In comparison, flavanone 3beta-hydroxylase catalyses hydroxylation at the C-3 pro-R position of 2S-naringenin. Incubation of ANS with the unnatural substrate (+/-)-naringenin results in predominantly C-3 hydroxylation to give cis-dihydrokaempferol as the major product; trans-dihydrokaempferol and the desaturation product, apigenin are also observed. Labelling studies have demonstrated that some of the formal desaturation reactions catalysed by ANS proceed via initial C-3 hydroxylation followed by dehydration at the active site. We describe analyses of the reaction of ANS with 2S- and 2R-naringenin substrates, including the anaerobic crystal structure of an ANS-Fe-2-oxoglutarate-naringenin complex. Together the results reveal that for the 'natural' C-2 stereochemistry of 2S-naringenin, C-3 hydroxylation predominates (>9 : 1) over desaturation, probably due to the inaccessibility of the C-2 hydrogen to the iron centre. For the 2R-naringenin substrate, desaturation is significantly increased relative to C-3 hydroxylation (ca. 1 : 1); this is probably a result of both the C-3 pro-S and C-2 hydrogen atoms being accessible to the reactive oxidising intermediate in this substrate. In contrast to the hydroxylation-elimination desaturation mechanism for some ANS substrates, the results imply that the ANS catalysed desaturation of 2R-naringenin to form apigenin proceeds with a syn-arrangement of eliminated hydrogen atoms and not via an oxygenated (gem-diol) flavonoid intermediate. Thus, by utilising flavonoid substrates with different C-2 stereochemistries, the balance between C-3 hydroxylation or C-2, C-3 desaturation mechanisms can be altered.
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Affiliation(s)
- Richard W D Welford
- Chemical Research Laboratory, Department of Chemistry and Oxford Centre for Molecular Sciences, Mansfield Road, Oxford OX1 3TA, UK
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42
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Searls T, Butler D, Chien W, Mukherji M, Lloyd MD, Schofield CJ. Studies on the specificity of unprocessed and mature forms of phytanoyl-CoA 2-hydroxylase and mutation of the iron binding ligands. J Lipid Res 2005; 46:1660-7. [PMID: 15930519 DOI: 10.1194/jlr.m500034-jlr200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mature form of phytanoyl-coenzyme A 2-hydroxylase (PAHX), a nonheme Fe(II)- and 2-oxoglutarate-dependent oxygenase, catalyzes the alpha-hydroxylation of phytanoyl-CoA within peroxisomes. Mutations in PAHX result in some forms of adult Refsum's disease. Unprocessed PAHX (pro-PAHX) contains an N-terminal peroxisomal targeting sequence that is cleaved to give mature PAHX (mat-PAHX). Previous studies have implied a difference in the substrate specificity of the unprocessed and mature forms of PAHX. We demonstrate that both forms are able to hydroxylate a range of CoA derivatives, but under the same assay conditions, the N-terminal hexa-His-tagged unprocessed form is less active than the nontagged mature form. Analyses of the assay conditions suggest a rationale for the lack of activity previously reported for some substrates (e.g. isovaleryl-CoA) for the (His)6pro-PAHX. Site-directed mutagenesis was used to support proposals for the identity of the iron binding ligands (His-175, Asp-177, His-264) of the 2-His-1-carboxylate motif of PAHX. Mutation of other histidine residues (His-213, His-220, His-259) suggested that these residues were not involved in Fe(II) binding.
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Affiliation(s)
- Timothy Searls
- Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK
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43
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Hewitson KS, Granatino N, Welford RWD, McDonough MA, Schofield CJ. Oxidation by 2-oxoglutarate oxygenases: non-haem iron systems in catalysis and signalling. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2005; 363:807-28; discussion 1035-40. [PMID: 15901537 DOI: 10.1098/rsta.2004.1540] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The 2-oxoglutarate (2OG) and ferrous iron dependent oxygenases are a superfamily of enzymes that catalyse a wide range of reactions including hydroxylations, desaturations and oxidative ring closures. Recently, it has been discovered that they act as sensors in the hypoxic response in humans and other animals. Substrate oxidation is coupled to conversion of 2OG to succinate and carbon dioxide. Kinetic, spectroscopic and structural studies are consistent with a consensus mechanism in which ordered binding of (co)substrates enables control of reactive intermediates. Binding of the substrate to the active site triggers the enzyme for ligation of dioxygen to the metal. Oxidative decarboxylation of 2OG then generates the ferryl species thought to mediate substrate oxidation. Structural studies reveal a conserved double-stranded beta-helix core responsible for binding the iron, via a 2His-1carboxylate motif and the 2OG side chain. The rigidity of this core contrasts with the conformational flexibility of surrounding regions that are involved in binding the substrate. Here we discuss the roles of 2OG oxygenases in terms of the generic structural and mechanistic features that render the 2OG oxygenases suited for their functions.
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Affiliation(s)
- K S Hewitson
- The Department of Chemistry and The Oxford Centre for Molecular Sciences, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK
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44
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Kershaw NJ, Caines MEC, Sleeman MC, Schofield CJ. The enzymology of clavam and carbapenem biosynthesis. Chem Commun (Camb) 2005:4251-63. [PMID: 16113715 DOI: 10.1039/b505964j] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The enzyme-catalysed reactions involved in formation of the bicyclic clavam and carbapenem nuclei, including beta-amino acid and beta-lactam formation, are discussed and compared with those involved in penicillin and cephalosporin biosynthesis. The common role of unusual oxidation reactions in the biosynthetic pathways and the lack of synthetic reagents available to effect them are highlighted.
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Affiliation(s)
- Nadia J Kershaw
- Department of Chemistry and Oxford Centre for Molecular Sciences, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
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45
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Abstract
4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an Fe(II)-dependent, non-heme oxygenase that catalyzes the conversion of 4-hydroxyphenylpyruvate to homogentisate. This reaction involves decarboxylation, substituent migration and aromatic oxygenation in a single catalytic cycle. HPPD is a member of the alpha-keto acid dependent oxygenases that typically require an alpha-keto acid (almost exclusively alpha-ketoglutarate) and molecular oxygen to either oxygenate or oxidize a third molecule. As an exception in this class of enzymes HPPD has only two substrates, does not use alpha-ketoglutarate, and incorporates both atoms of dioxygen into the aromatic product, homogentisate. The tertiary structure of the enzyme would suggest that its mechanism converged with that of other alpha-keto acid enzymes from an extradiol dioxygenase progenitor. The transformation catalyzed by HPPD has both agricultural and therapeutic significance. HPPD catalyzes the second step in the pathway for the catabolism of tyrosine, that is common to essentially all aerobic forms of life. In plants this pathway has an anabolic branch from homogentisate that forms essential isoprenoid redox cofactors such as plastoquinone and tocopherol. Naturally occurring multi-ketone molecules act as allelopathic agents by inhibiting HPPD and preventing the production of homogentisate and hence required redox cofactors. This has been the basis for the development of a range of very effective herbicides that are currently used commercially. In humans, deficiencies of specific enzymes of the tyrosine catabolism pathway give rise to a number of severe metabolic disorders. Interestingly, HPPD inhibitor/herbicide molecules act also as therapeutic agents for a number of debilitating and lethal inborn defects in tyrosine catabolism by preventing the accumulation of toxic metabolites.
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Affiliation(s)
- Graham R Moran
- Department of Chemistry and Biochemistry. University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA.
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46
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Oster LM, van Scheltinga ACT, Valegård K, Hose AM, Dubus A, Hajdu J, Andersson I. Conformational Flexibility of the C Terminus with Implications for Substrate Binding and Catalysis Revealed in a New Crystal Form of Deacetoxycephalosporin C Synthase. J Mol Biol 2004; 343:157-71. [PMID: 15381427 DOI: 10.1016/j.jmb.2004.07.049] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2004] [Revised: 07/12/2004] [Accepted: 07/15/2004] [Indexed: 11/18/2022]
Abstract
Deacetoxycephalosporin C synthase (DAOCS) from Streptomyces clavuligerus catalyses the oxidative ring expansion of the penicillin nucleus into the nucleus of cephalosporins. The reaction requires dioxygen and 2-oxoglutarate as co-substrates to create a reactive iron-oxygen intermediate from a ferrous iron in the active site. The active enzyme is monomeric in solution. The structure of DAOCS was determined earlier from merohedrally twinned crystals where the last four C-terminal residues (308-311) of one molecule penetrate the active site of a neighbouring molecule, creating a cyclic trimeric structure in the crystal. Shortening the polypeptide chain from the C terminus by more than four residues diminishes activity. Here, we describe a new crystal form of DAOCS in which trimer formation is broken and the C-terminal arm is free. These crystals show no signs of twinning, and were obtained from DAOCS labelled with an N-terminal His-tag. The modified DAOCS is catalytically active. The free C-terminal arm protrudes into the solvent, and the C-terminal domain (residues 268-299) is rotated by about 16 degrees towards the active site. The last 12 residues (300-311) are disordered. Structures for various enzyme-substrate and enzyme-product complexes in the new crystal form confirm overlapping binding sites for penicillin and 2-oxoglutarate. The results support the notion that 2-oxoglutarate and dioxygen need to react first to produce an oxidizing iron species, followed by reaction with the penicillin substrate. The position of the penicillin nucleus is topologically similar in the two crystal forms, but the penicillin side-chain in the new non-twinned crystals overlaps with the position of residues 304-306 of the C-terminal arm in the twinned crystals. An analysis of the interactions between the C-terminal region and residues in the active site indicates that DAOCS could also accept polypeptide chains as ligands, and these could bind near the iron.
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Affiliation(s)
- Linda M Oster
- Department of Molecular Biology, Swedish University of Agricultural Sciences, Box 590, S-75124 Uppsala
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47
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Zhang Z, Ren JS, Clifton IJ, Schofield CJ. Crystal Structure and Mechanistic Implications of 1-Aminocyclopropane-1-Carboxylic Acid Oxidase—The Ethylene-Forming Enzyme. ACTA ACUST UNITED AC 2004; 11:1383-94. [PMID: 15489165 DOI: 10.1016/j.chembiol.2004.08.012] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Revised: 07/15/2004] [Accepted: 08/02/2004] [Indexed: 10/26/2022]
Abstract
The final step in the biosynthesis of the plant signaling molecule ethylene is catalyzed by 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO). ACCO requires bicarbonate as an activator and catalyzes the oxidation of ACC to give ethylene, CO2, and HCN. We report crystal structures of ACCO in apo-form (2.1 A resolution) and complexed with Fe(II) (2.55 A) or Co(II) (2.4 A). The active site contains a single Fe(II) ligated by three residues (His177, Asp179, and His234), and it is relatively open compared to those of the 2-oxoglutarate oxygenases. The side chains of Arg175 and Arg244, proposed to be involved in binding bicarbonate, project away from the active site, but conformational changes may allow either or both to enter the active site. The structures will form a basis for future mechanistic and inhibition studies.
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Affiliation(s)
- Zhihong Zhang
- The Oxford Centre for Molecular Sciences, The Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, United Kingdom
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48
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Csokova N, Skrabana R, Liebig HD, Mederlyova A, Kontsek P, Novak M. Rapid purification of truncated tau proteins: model approach to purification of functionally active fragments of disordered proteins, implication for neurodegenerative diseases. Protein Expr Purif 2004; 35:366-72. [PMID: 15135415 DOI: 10.1016/j.pep.2004.01.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Revised: 01/15/2004] [Indexed: 11/27/2022]
Abstract
Truncated tau is of great interest because of its important role in neurofibrillary pathogenesis in Alzheimer's disease (AD). A major obstacle for characterization of detailed biochemical and biological properties of truncated tau species and their fragments has been the lack of reliable and quick purification methods. Uneven distribution of acidic and basic residues in tau determines that the N- and C-terminal tau fragments require entirely different purification conditions. Conventional methods take several days; they do not allow purification of the acidic N-terminal tau fragments and do not prevent aggregation during purification that makes purified truncated tau unusable in functional studies. To prevent these inherent problems, we have designed a two-step, highly efficient purification procedure yielding a fully functional, non-aggregated homogeneous population of truncated tau molecules. Various forms of tau produced in bacteria without the need for a heat pre-treatment step were subjected to anion- and cation-exchange chromatography. Conditions were developed that allowed effective separation and purification of acidic and/or basic tau species. Following the gel filtration step, up to 10mg of tau proteins with 96% purity was obtained within one working day. Purified truncated tau exhibited an unmodified immunoreactivity and allowed its functional activity analysis. Since many neurodegenerative diseases have implicated similar disordered proteins in their pathogenesis, our procedure will allow their detailed analysis and characterization.
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Affiliation(s)
- Natalia Csokova
- Institute of Neuroimmunology Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia
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49
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Chin HS, Goo KS, Sim TS. A complete library of amino acid alterations at N304 in Streptomyces clavuligerus deacetoxycephalosporin C synthase elucidates the basis for enhanced penicillin analogue conversion. Appl Environ Microbiol 2004; 70:607-9. [PMID: 14711695 PMCID: PMC321265 DOI: 10.1128/aem.70.1.607-609.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
N304 of Streptomyces clavuligerus deacetoxycephalosporin C synthase was mutagenized to alter its catalytic ability. Given that N304A, N304K, N304L, and N304R mutant enzymes exhibited significant improvements in penicillin analogue conversions, we advocate that replacement of N304 with residues with aliphatic or basic side chains is preferable for engineering of a hypercatalytic enzyme.
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Affiliation(s)
- Hong Soon Chin
- Department of Microbiology, Faculty of Medicine, Tropical Marine Science Institute, National University of Singapore, Singapore
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50
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Lloyd MD, Lipscomb SJ, Hewitson KS, Hensgens CMH, Baldwin JE, Schofield CJ. Controlling the Substrate Selectivity of Deacetoxycephalosporin/deacetylcephalosporin C Synthase. J Biol Chem 2004; 279:15420-6. [PMID: 14734549 DOI: 10.1074/jbc.m313928200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Deacetoxycephalosporin/deacetylcephalosporin C synthase (DAOC/DACS) is an iron(II) and 2-oxoglutarate-dependent oxygenase involved in the biosynthesis of cephalosporin C in Cephalosporium acremonium. It catalyzes two oxidative reactions, oxidative ring-expansion of penicillin N to deacetoxycephalosporin C, and hydroxylation of the latter to give deacetylcephalosporin C. The enzyme is closely related to deacetoxycephalosporin C synthase (DAOCS) and DACS from Streptomyces clavuligerus, which selectively catalyze ring-expansion or hydroxylation reactions, respectively. In this study, structural models based on DAOCS coupled with site-directed mutagenesis were used to identify residues within DAOC/DACS that are responsible for controlling substrate and reaction selectivity. The M306I mutation abolished hydroxylation of deacetylcephalosporin C, whereas the W82A mutant reduced ring-expansion of penicillin G (an "unnatural" substrate). Truncation of the C terminus of DAOC/DACS to residue 310 (Delta310 mutant) enhanced ring-expansion of penicillin G by approximately 2-fold. A double mutant, Delta310/M306I, selectively catalyzed the ring-expansion reaction and had similar kinetic parameters to the wild-type DAOC/DACS. The Delta310/N305L/M306I triple mutant selectively catalyzed ring-expansion of penicillin G and had improved kinetic parameters (K(m) = 2.00 +/- 0.47 compared with 6.02 +/- 0.97 mm for the wild-type enzyme). This work demonstrates that a single amino acid residue side chain within the DAOC/DACS active site can control whether the enzyme catalyzes ring-expansion, hydroxylation, or both reactions. The catalytic efficiency of mutant enzymes can be improved by combining active site mutations with other modifications including C-terminal truncation and modification of Asn-305.
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Affiliation(s)
- Matthew D Lloyd
- Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.
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