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Groves JT, Feng L, Austin RN. Structure and Function of Alkane Monooxygenase (AlkB). Acc Chem Res 2023; 56:3665-3675. [PMID: 38032826 DOI: 10.1021/acs.accounts.3c00590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Every year, perhaps as much as 800 million tons of hydrocarbons enters the environment; alkanes make up a large percentage of it. Most are transformed by organisms that utilize these molecules as sources of energy and carbon. Both aerobic and anaerobic alkane transformation chemistries exist, capitalizing on the presence of alkanes in both oxic and anoxic environments. Over the past 40 years, tremendous progress has been made in understanding the structure and mechanism of enzymes that catalyze the transformation of methane. By contrast, progress involving enzymes that transform liquid alkanes has been slower with the first structures of AlkB, the predominant aerobic alkane hydroxylase in the environment, appearing in 2023. Because of the fundamental importance of C-H bond activation chemistries, interest in understanding how biology activates and transforms alkanes is high.In this Account, we focus on steps we have taken to understand the mechanism and structure of alkane monooxygenase (AlkB), the metalloenzyme that dominates the transformation of liquid alkanes in the environment (not to be confused with another AlkB that is an α-ketogluturate-dependent enzyme involved in DNA repair). First, we briefly describe what is known about the prevalence of AlkB in the environment and its role in the carbon cycle. Then we review the key findings from our recent high-resolution cryoEM structure of AlkB and highlight important similarities and differences in the structures of members of class III diiron enzymes. Functional studies, which we summarize, from a number of single residue variants enable us to say a great deal about how the structure of AlkB facilitates its function. Next, we overview work from our laboratories using mechanistically diagnostic radical clock substrates to characterize the mechanism of AlkB and contextualize the results we have obtained on AlkB with results we have obtained on other alkane-oxidizing enzymes and explain these results in light of the enzyme's structure. Finally, we integrate recent work in our laboratories with information from prior studies of AlkB, and relevant model systems, to create a holistic picture of the enzyme. We end by pointing to critical questions that still need to be answered, questions about the electronic structure of the active site of the enzyme throughout the reaction cycle and about whether and to what extent the enzyme plays functional roles in biology beyond simply initiating the degradation of alkanes.
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Affiliation(s)
- John T Groves
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Liang Feng
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, United States
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Williams SC, Luongo D, Orman M, Vizcarra CL, Austin RN. An alkane monooxygenase (AlkB) family in which all electron transfer partners are covalently bound to the oxygen-activating hydroxylase. J Inorg Biochem 2022; 228:111707. [PMID: 34990970 PMCID: PMC8799515 DOI: 10.1016/j.jinorgbio.2021.111707] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/13/2021] [Accepted: 12/29/2021] [Indexed: 10/19/2022]
Abstract
Alkane monooxygenase (AlkB) is a non-heme diiron enzyme that catalyzes the hydroxylation of alkanes. It is commonly found in alkanotrophic organisms that can live on alkanes as their sole source of carbon and energy. Activation of AlkB occurs via two-electron reduction of its diferric active site, which facilitates the binding, activation, and cleavage of molecular oxygen for insertion into an inert CH bond. Electrons are typically supplied by NADH via a rubredoxin reductase (AlkT) to a rubredoxin (AlkG) to AlkB, although alternative electron transfer partners have been observed. Here we report a family of AlkBs in which both electron transfer partners (a ferredoxin and a ferredoxin reductase) appear as an N-terminal gene fusion to the hydroxylase (ferr_ferrR_AlkB). This enzyme catalyzes the hydroxylation of medium chain alkanes (C6-C14), with a preference for C10-C12. It requires only NADH for activity. It is present in a number of bacteria that are known to be human pathogens. A survey of the genome neighborhoods in which is it found suggest it may be involved in alkane metabolism, perhaps facilitating growth of pathogens in non-host environments.
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Mondal S, Dumur F, Gigmes D, Sibi MP, Bertrand MP, Nechab M. Enantioselective Radical Reactions Using Chiral Catalysts. Chem Rev 2022; 122:5842-5976. [DOI: 10.1021/acs.chemrev.1c00582] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Shovan Mondal
- Department of Chemistry, Syamsundar College, Shyamsundar 713424, West Bengal, India
| | - Frédéric Dumur
- Aix Marseille Univ, CNRS, Institut de Chimie Radicalaire UMR 7273, F-13390e Marseille, France
| | - Didier Gigmes
- Aix Marseille Univ, CNRS, Institut de Chimie Radicalaire UMR 7273, F-13390e Marseille, France
| | - Mukund P. Sibi
- Department of Chemistry and Biochemistry North Dakota State University, Fargo, North Dakota 58108, United States
| | - Michèle P. Bertrand
- Aix Marseille Univ, CNRS, Institut de Chimie Radicalaire UMR 7273, F-13390e Marseille, France
| | - Malek Nechab
- Aix Marseille Univ, CNRS, Institut de Chimie Radicalaire UMR 7273, F-13390e Marseille, France
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Yang HC, Ge YC, Yang CH, Chao WC. Substrate Channeling of Prostaglandin H2 on the Stereochemical Control of a Cascade Cyclization Route. ACS Catal 2018. [DOI: 10.1021/acscatal.7b03687] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hsiao-Ching Yang
- Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan
| | - Yung-Chi Ge
- Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan
| | - Cheng-Han Yang
- Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan
| | - Wei-Chih Chao
- Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan
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Hsieh CH, Huang X, Amaya JA, Rutland CD, Keys CL, Groves JT, Austin RN, Makris TM. The Enigmatic P450 Decarboxylase OleT Is Capable of, but Evolved To Frustrate, Oxygen Rebound Chemistry. Biochemistry 2017; 56:3347-3357. [PMID: 28603981 DOI: 10.1021/acs.biochem.7b00338] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OleT is a cytochrome P450 enzyme that catalyzes the removal of carbon dioxide from variable chain length fatty acids to form 1-alkenes. In this work, we examine the binding and metabolic profile of OleT with shorter chain length (n ≤ 12) fatty acids that can form liquid transportation fuels. Transient kinetics and product analyses confirm that OleT capably activates hydrogen peroxide with shorter substrates to form the high-valent intermediate Compound I and largely performs C-C bond scission. However, the enzyme also produces fatty alcohol side products using the high-valent iron oxo chemistry commonly associated with insertion of oxygen into hydrocarbons. When presented with a short chain fatty acid that can initiate the formation of Compound I, OleT oxidizes the diagnostic probe molecules norcarane and methylcyclopropane in a manner that is reminiscent of reactions of many CYP hydroxylases with radical clock substrates. These data are consistent with a decarboxylation mechanism in which Compound I abstracts a substrate hydrogen atom in the initial step. Positioning of the incipient substrate radical is a crucial element in controlling the efficiency of activated OH rebound.
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Affiliation(s)
- Chun H Hsieh
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Xiongyi Huang
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - José A Amaya
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Cooper D Rutland
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - Carson L Keys
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
| | - John T Groves
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Rachel N Austin
- Department of Chemistry, Barnard College, Columbia University , New York, New York 10027, United States
| | - Thomas M Makris
- Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States
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Liu W, Cheng MJ, Nielsen RJ, Goddard WA, Groves JT. Probing the C–O Bond-Formation Step in Metalloporphyrin-Catalyzed C–H Oxygenation Reactions. ACS Catal 2017. [DOI: 10.1021/acscatal.7b00655] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wei Liu
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Mu-Jeng Cheng
- Department
of Chemistry, Materials and Process Simulation Center (MC 139-74), California Institute of Technology, Pasadena, California 91125, United States
- Department
of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Robert J. Nielsen
- Department
of Chemistry, Materials and Process Simulation Center (MC 139-74), California Institute of Technology, Pasadena, California 91125, United States
| | - William A. Goddard
- Department
of Chemistry, Materials and Process Simulation Center (MC 139-74), California Institute of Technology, Pasadena, California 91125, United States
| | - John T. Groves
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Abstract
The remarkable aliphatic C-H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species that transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon-halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C-H bonds to C-Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L-Mn(V)═O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn-F fluorine source, effecting carbon-fluorine bond formation. Indeed, this idea led to the discovery of the first Mn-catalyzed direct aliphatic C-H fluorination reactions utilizing simple, nucleophilic fluoride salts. Mechanistic studies and DFT calculations have revealed a trans-difluoromanganese(IV) species as the key fluorine transfer intermediate. In addition to catalyzing normal (19)F-fluorination reactions, manganese salen complexes were found to enable the incorporation of radioactive (18)F fluorine via C-H activation. This advance represented the first direct Csp(3)-H bond (18)F labeling with no-carrier-added [(18)F]fluoride and facilitated the late-stage labeling of drug molecules for PET imaging. Given the high reactivity and enzymatic-like selectively of metalloporphyrins, we envision that this new Heteroatom-Rebound Catalysis (HRC) strategy will find widespread application in the C-H functionalization arena and serve as an effective tool for forming new carbon-heteroatom bonds at otherwise inaccessible sites in target molecules.
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Affiliation(s)
- Wei Liu
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - John T. Groves
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Bertrand EM, Keddis R, Groves JT, Vetriani C, Austin RN. Identity and mechanisms of alkane-oxidizing metalloenzymes from deep-sea hydrothermal vents. Front Microbiol 2013; 4:109. [PMID: 23825470 PMCID: PMC3695450 DOI: 10.3389/fmicb.2013.00109] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 04/16/2013] [Indexed: 12/21/2022] Open
Abstract
Six aerobic alkanotrophs (organism that can metabolize alkanes as their sole carbon source) isolated from deep-sea hydrothermal vents were characterized using the radical clock substrate norcarane to determine the metalloenzyme and reaction mechanism used to oxidize alkanes. The organisms studied were Alcanivorax sp. strains EPR7 and MAR14, Marinobacter sp. strain EPR21, Nocardioides sp. strains EPR26w, EPR28w, and Parvibaculum hydrocarbonoclasticum strain EPR92. Each organism was able to grow on n-alkanes as the sole carbon source and therefore must express genes encoding an alkane-oxidizing enzyme. Results from the oxidation of the radical-clock diagnostic substrate norcarane demonstrated that five of the six organisms (EPR7, MAR14, EPR21, EPR26w, and EPR28w) used an alkane hydroxylase functionally similar to AlkB to catalyze the oxidation of medium-chain alkanes, while the sixth organism (EPR92) used an alkane-oxidizing cytochrome P450 (CYP)-like protein to catalyze the oxidation. DNA sequencing indicated that EPR7 and EPR21 possess genes encoding AlkB proteins, while sequencing results from EPR92 confirmed the presence of a gene encoding CYP-like alkane hydroxylase, consistent with the results from the norcarane experiments.
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Affiliation(s)
- Erin M Bertrand
- Department of Chemistry, Bates College Lewiston, ME, USA ; Microbial and Environmental Genomics, J. Craig Venter Institute San Diego, CA, USA
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Abstract
Cytochrome P450 enzymes primarily catalyze mixed-function oxidation reactions, plus some reductions and rearrangements of oxygenated species, e.g. prostaglandins. Most of these reactions can be rationalized in a paradigm involving Compound I, a high-valent iron-oxygen complex (FeO(3+)), to explain seemingly unusual reactions, including ring couplings, ring expansion and contraction, and fusion of substrates. Most P450s interact with flavoenzymes or iron-sulfur proteins to receive electrons from NAD(P)H. In some cases, P450s are fused to protein partners. Other P450s catalyze non-redox isomerization reactions. A number of permutations on the P450 theme reveal the diversity of cytochrome P450 form and function.
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Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
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Naing SH, Parvez S, Pender-Cudlip M, Groves JT, Austin RN. Substrate specificity and reaction mechanism of purified alkane hydroxylase from the hydrocarbonoclastic bacterium Alcanivorax borkumensis (AbAlkB). J Inorg Biochem 2013; 121:46-52. [PMID: 23337786 PMCID: PMC3595352 DOI: 10.1016/j.jinorgbio.2012.12.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 12/13/2012] [Accepted: 12/14/2012] [Indexed: 10/27/2022]
Abstract
An alkane hydroxylase from the marine organism Alcanivorax borkumensis (AbAlkB) was purified. The purified protein retained high activity in an assay with purified rubredoxin (AlkG), purified maize ferredoxin reductase, NADPH, and selected substrates. The reaction mechanism of the purified protein was probed using the radical clock substrates bicyclo[4.1.0]heptane (norcarane), bicyclo[3.1.0]hexane (bicyclohexane), methylphenylcyclopropane and deuterated and non-deuterated cyclohexane. The distribution of products from the radical clock substrates supports the hypothesis that purified AbAlkB hydroxylates substrates by forming a substrate radical. Experiments with deuterated cyclohexane indicate that the rate-determining step has a significant CH bond breaking character. The products formed from a number of differently shaped and sized substrates were characterized to determine the active site constraints of this AlkB. AbAlkB can catalyze the hydroxylation of a large number of aromatic compounds and linear and cyclic alkanes. It does not catalyze the hydroxylation of alkanes with a chain length longer than 15 carbons, nor does it hydroxylate sterically hindered C-H bonds.
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Affiliation(s)
- Swe-Htet Naing
- Department of Chemistry, Bates College, 5 Andrews Rd. Lewiston ME 04240, 207-786-6295, fax: 207-786-8336
| | - Saba Parvez
- Department of Chemistry, Bates College, 5 Andrews Rd. Lewiston ME 04240, 207-786-6295, fax: 207-786-8336
| | - Marilla Pender-Cudlip
- Department of Chemistry, Bates College, 5 Andrews Rd. Lewiston ME 04240, 207-786-6295, fax: 207-786-8336
| | - John T. Groves
- Department of Chemistry, Princeton University, Princeton NJ 08544
| | - Rachel N. Austin
- Department of Chemistry, Bates College, 5 Andrews Rd. Lewiston ME 04240, 207-786-6295, fax: 207-786-8336
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11
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Cooper HLR, Mishra G, Huang X, Pender-Cudlip M, Austin RN, Shanklin J, Groves JT. Parallel and competitive pathways for substrate desaturation, hydroxylation, and radical rearrangement by the non-heme diiron hydroxylase AlkB. J Am Chem Soc 2012; 134:20365-75. [PMID: 23157204 PMCID: PMC3531984 DOI: 10.1021/ja3059149] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A purified and highly active form of the non-heme diiron hydroxylase AlkB was investigated using the diagnostic probe substrate norcarane. The reaction afforded C2 (26%) and C3 (43%) hydroxylation and desaturation products (31%). Initial C-H cleavage at C2 led to 7% C2 hydroxylation and 19% 3-hydroxymethylcyclohexene, a rearrangement product characteristic of a radical rearrangement pathway. A deuterated substrate analogue, 3,3,4,4-norcarane-d(4), afforded drastically reduced amounts of C3 alcohol (8%) and desaturation products (5%), while the radical rearranged alcohol was now the major product (65%). This change in product ratios indicates a large kinetic hydrogen isotope effect of ∼20 for both the C-H hydroxylation at C3 and the desaturation pathway, with all of the desaturation originating via hydrogen abstraction at C3 and not C2. The data indicate that AlkB reacts with norcarane via initial C-H hydrogen abstraction from C2 or C3 and that the three pathways, C3 hydroxylation, C3 desaturation, and C2 hydroxylation/radical rearrangement, are parallel and competitive. Thus, the incipient radical at C3 either reacts with the iron-oxo center to form an alcohol or proceeds along the desaturation pathway via a second H-abstraction to afford both 2-norcarene and 3-norcarene. Subsequent reactions of these norcarenes lead to detectable amounts of hydroxylation products and toluene. By contrast, the 2-norcaranyl radical intermediate leads to C2 hydroxylation and the diagnostic radical rearrangement, but this radical apparently does not afford desaturation products. The results indicate that C-H hydroxylation and desaturation follow analogous stepwise reaction channels via carbon radicals that diverge at the product-forming step.
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Affiliation(s)
| | - Girish Mishra
- Department of Biology, Brookhaven National Laboratory, 50 Bell Avenue, Upton, NY 11973
| | - Xiongyi Huang
- Department of Chemistry, Princeton University, Princeton NJ 08544
| | | | | | - John Shanklin
- Department of Biology, Brookhaven National Laboratory, 50 Bell Avenue, Upton, NY 11973
| | - John T. Groves
- Department of Chemistry, Princeton University, Princeton NJ 08544
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12
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Bordeaux M, Galarneau A, Drone J. Catalytic, Mild, and Selective Oxyfunctionalization of Linear Alkanes: Current Challenges. Angew Chem Int Ed Engl 2012; 51:10712-23. [DOI: 10.1002/anie.201203280] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Indexed: 02/02/2023]
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Bordeaux M, Galarneau A, Drone J. Katalytische, milde und selektive Oxyfunktionalisierung von linearen Alkanen: aktuelle Herausforderungen. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203280] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Peter S, Kinne M, Wang X, Ullrich R, Kayser G, Groves JT, Hofrichter M. Selective hydroxylation of alkanes by an extracellular fungal peroxygenase. FEBS J 2011; 278:3667-75. [PMID: 21812933 DOI: 10.1111/j.1742-4658.2011.08285.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H(2)O(2) as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H(2)O(2)-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H(2)(18)(2) resulted in complete incorporation of (18)O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D(7) showed a large intramolecular deuterium isotope effect [(k(H)/k(D))(obs)] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 10(11) s(-1). These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C(16)) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood.
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Affiliation(s)
- Sebastian Peter
- Department of Bio- and Environmental Sciences, International Graduate School of Zittau, Zittau, Germany
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15
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Cooper HLR, Groves JT. Molecular probes of the mechanism of cytochrome P450. Oxygen traps a substrate radical intermediate. Arch Biochem Biophys 2011; 507:111-8. [PMID: 21075070 PMCID: PMC3041850 DOI: 10.1016/j.abb.2010.11.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 11/05/2010] [Accepted: 11/05/2010] [Indexed: 01/05/2023]
Abstract
The diagnostic substrate tetramethylcyclopropane (TMCP) has been reexamined as a substrate with three drug- and xenobiotic-metabolizing cytochrome P450 enzymes, human CYP2E1, CYP3A4 and rat CYP2B1. The major hydroxylation product in all cases was the unrearranged primary alcohol along with smaller amounts of a rearranged tertiary alcohol. Significantly, another ring-opened product, diacetone alcohol, was also observed. With CYP2E1 this product accounted for 20% of the total turnover. Diacetone alcohol also was detected as a product from TMCP with a biomimetic model catalyst, FeTMPyP, but not with a ruthenium porphyrin catalyst. Lifetimes of the intermediate radicals were determined from the ratios of rearranged and unrearranged products to be 120, 13 and 1ps for CYP2E1, CYP3A4 and CYP2B1, respectively, corresponding to rebound rates of 0.9×10(10)s(-1), 7.2×10(10)s(-1) and 1.0×10(12)s(-1). For the model iron porphyrin, FeTMPyP, a radical lifetime of 81ps and a rebound rate of 1.2×10(10)s(-1) were determined. These apparent radical lifetimes are consistent with earlier reports with a variety of CYP enzymes and radical clock substrates, however, the large amounts of diacetone alcohol with CYP2E1 and the iron porphyrin suggest that for these systems a considerable amount of the intermediate carbon radical is trapped by molecular oxygen. These results add to the view that cage escape of the intermediate carbon radical in [Fe(IV)-OH ()R] can compete with cage collapse to form a C-O bond. The results could be significant with regard to our understanding of iron-catalyzed C-H hydroxylation, the observation of P450-dependent peroxidation and the development of oxidative stress, especially for CYP2E1.
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Affiliation(s)
| | - John T. Groves
- Department of Chemistry, Princeton University, Princeton NJ 08544 USA
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Abstract
Oxygenated heme proteins are known to react rapidly with nitric oxide (NO) to produce peroxynitrite (PN) at the heme site. This process could lead either to attenuation of the effects of NO or to nitrosative protein damage. PN is a powerful nitrating and oxidizing agent that has been implicated in a variety of cell injuries. Accordingly, it is important to delineate the nature and variety of reaction mechanisms of PN interactions with heme proteins. In this Forum, we survey the range of reactions of PN with heme proteins, with particular attention to myoglobin and cytochrome c. While these two proteins are textbook paradigms for oxygen binding and electron transfer, respectively, both have recently been shown to have other important functions that involve NO and PN. We have recently described direct evidence that ferrylmyolgobin (ferrylMb) and nitrogen dioxide (NO(2)) are both produced during the reaction of PN and metmyolgobin (metMb) (Su, J.; Groves, J. T. J. Am. Chem. Soc. 2009, 131, 12979-12988). Kinetic evidence indicates that these products evolve from the initial formation of a caged radical intermediate [Fe(IV) horizontal lineO.NO(2)]. This caged pair reacts mainly via internal return with a rate constant k(r) to form metMb and nitrate in an oxygen-rebound scenario. Detectable amounts of ferrylMb are observed by stopped-flow spectrophotometry, appearing at a rate consistent with the rate, k(obs), of heme-mediated PN decomposition. Freely diffusing NO(2), which is liberated concomitantly from the radical pair (k(e)), preferentially nitrates myoglobin Tyr103 and added fluorescein. For cytochrome c, Raman spectroscopy has revealed that a substantial fraction of cytochrome c converts to a beta-sheet structure, at the expense of turns and helices at low pH (Balakrishnan, G.; Hu, Y.; Oyerinde, O. F.; Su, J.; Groves, J. T.; Spiro, T. G. J. Am. Chem. Soc., 2007, 129, 504-505). It is proposed that a short beta-sheet segment, comprising residues 37-39 and 58-61, extends itself into the large 37-61 loop when the latter is destabilized by protonation of H26, which forms an anchoring hydrogen bond to loop residue P44. This conformation change ruptures the Met80-Fe bond, as revealed by changes in ligation-sensitive Raman bands. It also induces peroxidase activity with the same temperature profile. This process is suggested to model the apoptotic peroxidation of cardiolipin by cytochrome c.
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Affiliation(s)
- Jia Su
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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Rabe V, Frey W, Baro A, Laschat S, Bauer M, Bertagnolli H, Rajagopalan S, Asthalter T, Roduner E, Dilger H, Glaser T, Schnieders D. Syntheses, Crystal Structures, Spectroscopic Properties, and Catalytic Aerobic Oxidations of Novel Trinuclear Non-Heme Iron Complexes. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200900516] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Francis K, Gadda G. Inflated Kinetic Isotope Effects in the Branched Mechanism of Neurospora crassa 2-Nitropropane Dioxygenase. Biochemistry 2009; 48:2403-10. [DOI: 10.1021/bi802238j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kevin Francis
- Departments of Chemistry and Biology and The Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-4098
| | - Giovanni Gadda
- Departments of Chemistry and Biology and The Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-4098
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Kobayashi H, Yamanaka I. Oxidation of adamantane with O2 catalysed by VO(acac)2 and reactivity of active species in acetic acid. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/j.molcata.2008.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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Austin RN, Luddy K, Erickson K, Pender-Cudlip M, Bertrand E, Deng D, Buzdygon RS, van Beilen JB, Groves JT. Cage escape competes with geminate recombination during alkane hydroxylation by the diiron oxygenase AlkB. Angew Chem Int Ed Engl 2008; 47:5232-4. [PMID: 18512839 DOI: 10.1002/anie.200801184] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Rachel N Austin
- Department of Chemistry, Bates College, Lewiston ME 04240, USA.
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Austin R, Luddy K, Erickson K, Pender‐Cudlip M, Bertrand E, Deng D, Buzdygon R, van Beilen J, Groves J. Cage Escape Competes with Geminate Recombination during Alkane Hydroxylation by the Diiron Oxygenase AlkB. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200801184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Rozhkova-Novosad EA, Chae JC, Zylstra GJ, Bertrand EM, Alexander-Ozinskas M, Deng D, Moe LA, van Beilen JB, Danahy M, Groves JT, Austin RN. Profiling mechanisms of alkane hydroxylase activity in vivo using the diagnostic substrate norcarane. ACTA ACUST UNITED AC 2007; 14:165-72. [PMID: 17317570 DOI: 10.1016/j.chembiol.2006.12.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Revised: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 10/23/2022]
Abstract
Mechanistically informative chemical probes are used to characterize the activity of functional alkane hydroxylases in whole cells. Norcarane is a substrate used to reveal the lifetime of radical intermediates formed during alkane oxidation. Results from oxidations of this probe with organisms that contain the two most prevalent medium-chain-length alkane-oxidizing metalloenzymes, alkane omega-monooxygenase (AlkB) and cytochrome P450 (CYP), are reported. The results--radical lifetimes of 1-7 ns for AlkB and less than 100 ps for CYP--indicate that these two classes of enzymes are mechanistically distinguishable and that whole-cell mechanistic assays can identify the active hydroxylase. The oxidation of norcarane by several recently isolated strains (Hydrocarboniphaga effusa AP103, rJ4, and rJ5, whose alkane-oxidizing enzymes have not yet been identified) is also reported. Radical lifetimes of 1-3 ns are observed, consistent with these organisms containing an AlkB-like enzyme and inconsistent with their employing a CYP-like enzyme for growth on hydrocarbons.
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Chakrabarty S, Austin RN, Deng D, Groves JT, Lipscomb JD. Radical intermediates in monooxygenase reactions of rieske dioxygenases. J Am Chem Soc 2007; 129:3514-5. [PMID: 17341076 PMCID: PMC2720596 DOI: 10.1021/ja068188v] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sarmistha Chakrabarty
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | | | - Dayi Deng
- Department of Chemistry, Princeton University, Princeton, NJ 08544
| | - John T. Groves
- Department of Chemistry, Princeton University, Princeton, NJ 08544
| | - John D. Lipscomb
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
- E-mail:
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25
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van Beilen JB, Funhoff EG. Alkane hydroxylases involved in microbial alkane degradation. Appl Microbiol Biotechnol 2007; 74:13-21. [PMID: 17216462 DOI: 10.1007/s00253-006-0748-0] [Citation(s) in RCA: 300] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 11/03/2006] [Accepted: 11/05/2006] [Indexed: 11/30/2022]
Abstract
This review focuses on the role and distribution in the environment of alkane hydroxylases and their (potential) applications in bioremediation and biocatalysis. Alkane hydroxylases play an important role in the microbial degradation of oil, chlorinated hydrocarbons, fuel additives, and many other compounds. Environmental studies demonstrate the abundance of alkane degraders and have lead to the identification of many new species, including some that are (near)-obligate alkanotrophs. The availability of a growing collection of alkane hydroxylase gene sequences now allows estimations of the relative abundance of the different enzyme systems and the distribution of the host organisms.
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Affiliation(s)
- Jan B van Beilen
- Département de Biologie Moléculaire Végétale, Le Biophore, Quartier Sorge, Université de Lausanne, 1015, Lausanne, Switzerland.
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