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Darbyshire AL, Wolthers KR. Characterization of a Structurally Distinct ATP-Dependent Reactivating Factor of Adenosylcobalamin-Dependent Lysine 5,6-Aminomutase. Biochemistry 2024; 63:913-925. [PMID: 38471967 DOI: 10.1021/acs.biochem.3c00653] [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: 03/14/2024]
Abstract
Several anaerobic bacterial species, including the Gram-negative oral bacterium Fusobacterium nucleatum, ferment lysine to produce butyrate, acetate, and ammonia. The second step of the metabolic pathway─isomerization of β-l-lysine to erythro-3,5-diaminohexanoate─is catalyzed by the adenosylcobalamin (AdoCbl) and pyridoxal 5'-phosphate (PLP)-dependent enzyme, lysine 5,6-aminomutase (5,6-LAM). Similar to other AdoCbl-dependent enzymes, 5,6-LAM undergoes mechanism-based inactivation due to loss of the AdoCbl 5'-deoxyadenosyl moiety and oxidation of the cob(II)alamin intermediate to hydroxocob(III)alamin. Herein, we identified kamB and kamC, two genes responsible for ATP-dependent reactivation of 5,6-LAM. KamB and KamC, which are encoded upstream of the genes corresponding to α and β subunits of 5,6-LAM (kamD and kamE), co-purified following coexpression of the genes in Escherichia coli. KamBC exhibited a basal level of ATP-hydrolyzing activity that was increased 35% in a reaction mixture that facilitated 5,6-LAM turnover with β-l-lysine or d,l-lysine. Ultraviolet-visible (UV-vis) spectroscopic studies performed under anaerobic conditions revealed that KamBC in the presence of ATP/Mg2+ increased the steady-state concentration of the cob(II)alamin intermediate in the presence of excess β-l-lysine. Using a coupled UV-visible spectroscopic assay, we show that KamBC is able to reactivate 5,6-LAM through exchange of the damaged hydroxocob(III)alamin for AdoCbl. KamBC is also specific for 5,6-LAM as it had no effect on the rate of substrate-induced inactivation of the homologue, ornithine 4,5-aminomutase. Based on sequence homology, KamBC is structurally distinct from previously characterized B12 chaperones and reactivases, and correspondingly adds to the list of proteins that have evolved to maintain the cellular activity of B12 enzymes.
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Affiliation(s)
- Amanda L Darbyshire
- Department of Chemistry, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna V1V 1V7, Canada
| | - Kirsten R Wolthers
- Department of Chemistry, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna V1V 1V7, Canada
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2
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Hands-Portman I, Bakker SE. Customising the plunge-freezing workflow for challenging conditions. Faraday Discuss 2022; 240:44-54. [PMID: 35913403 PMCID: PMC9641998 DOI: 10.1039/d2fd00060a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Grid freezing is a critical step for successful cryo-transmission electron microscopy, and optimising freezing conditions is a considerable bottleneck in many projects. To improve reproducibility in grid preparation, temperature- and humidity-controlled chambers were built into the second generation of plunge-freezers, including the ThermoFisherScientific Vitrobot and Leica GP. Since then, for most published structures, the proteins were plunge-frozen from a cold, humid environment. This provides two benefits: many proteins are more stable at 4 °C than room temperature, and both the low temperature and the humidity help control evaporation of the tiny drop of liquid. However, for optimal stability, certain samples may have different requirements. Here, we describe various (reversible) adaptations made to a Leica GP2 system to accommodate several samples with special handling requirements: a protein that is sensitive to both light and oxygen, a sample that needs to be kept at 37 °C throughout the plunge-freezing process, and a method to freeze a polymer that gels at 37 °C in its gelled state. While some of these methods are specific to these specimens, we hope sharing the ideas behind them will help people who are dealing with tricky protein samples.
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Affiliation(s)
- Ian Hands-Portman
- Advanced Bioimaging Research Technology Platform, University of WarwickGibbet Hill RoadCoventryCV4 7ALUK
| | - Saskia E. Bakker
- Advanced Bioimaging Research Technology Platform, University of WarwickGibbet Hill RoadCoventryCV4 7ALUK
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3
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Maity AN, Chen JR, Ke SC. Exploring the mechanism of action of lysine 5,6-aminomutase using EPR and ENDOR spectroscopies. Methods Enzymol 2022; 669:197-228. [PMID: 35644172 DOI: 10.1016/bs.mie.2021.12.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Radical enzymes orchestrate challenging chemical transformations by devising strategies to tame the highly reactive radical intermediates. Electron paramagnetic resonance (EPR) spectroscopy is the most suitable technique to study various aspects of the radical enzymes. Lysine 5,6-aminomutase (5,6-LAM) is one such radical enzyme and employs coenzyme B12 and pyridoxal 5'-phosphate (PLP) to catalyze the 1,2-amino shift reaction through a radical mechanism. 5,6-LAM accepts either d-lysine or l-β-lysine as the substrate. EPR and electron nuclear double resonance (ENDOR) spectroscopies have played major roles in deciphering the mechanism of action of 5,6-LAM, while density functional theoretical (DFT) computation and synthetic isotopologues have played supporting roles. This comprehensive toolkit has revealed that 5,6-LAM undergoes large-scale conformational movement to bring PLP and coenzyme B12 close together, which allows the reaction to progress. The conformational change also closes the active site, which protects the radical intermediates and enables their transformation to product without unwanted side reactions. The substrate-related radical (S•), which is spin-coupled with Co2+ generated from homolysis of the CoC bond in coenzyme B12, was unequivocally characterized when a substrate analog, 4-thia-l-lysine, and isotopologues of it were reacted with 5,6-LAM. Studies with substrate analogs revealed a unique "odd-even" correlation with opening of the closed state. Moreover, mutagenesis studies identified the contributions that conserved residues in 5,6-LAM make toward binding of the substrate. Further studies with a cofactor analog, PLP-N-oxide, have shed light on various aspects of the mechanism of action of 5,6-LAM.
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Affiliation(s)
| | - Jun-Ru Chen
- Department of Physics, National Dong Hwa University, Hualien, Taiwan
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Hualien, Taiwan.
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4
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Darbyshire AL, Makins C, Wolthers KR. Steady-state and pre-steady state kinetic analysis of ornithine 4,5-aminomutase. Methods Enzymol 2022; 669:173-195. [PMID: 35644171 DOI: 10.1016/bs.mie.2021.11.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ornithine 4,5-aminomutase (4,5-OAM) is a pyridoxal 5'-phosphate and adenosylcobalamin-dependent enzyme that catalyzes a 1,2-rearrangement of the terminal amine of d-ornithine to form (2R, 4S)-diaminopentanoate. The gene encoding ornithine 4,5-aminomutase is clustered with other genes that function in the oxidative l-ornithine metabolic pathway present in a number of anaerobic bacteria. This chapter discusses the methodology for measuring 4,5-OAM activity using NAD+-dependent diaminopentanoate dehydrogenase, which functions downstream of 4,5-OAM in the l-ornithine metabolic pathway. The use of ornithine racemace, which functions upstream of 4,5-OAM, for the synthesis of d,l-ornithine-3,3,4,4,5,5-d6 is also presented. Finally, this chapter describes the anaerobic stopped-flow spectrophotometric analysis of 4,5-OAM. Information is provided on the integration of a stopped-flow system in the anaerobically-maintained glove, the preparation of anaerobic solutions, and the experimental approach.
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Affiliation(s)
- Amanda L Darbyshire
- Department of Chemistry, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Caitlyn Makins
- Department of Chemistry, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Kirsten R Wolthers
- Department of Chemistry, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada.
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5
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Tran JU, Brown BL. Structural Basis for Allostery in PLP-dependent Enzymes. Front Mol Biosci 2022; 9:884281. [PMID: 35547395 PMCID: PMC9081730 DOI: 10.3389/fmolb.2022.884281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
Pyridoxal 5'-phosphate (PLP)-dependent enzymes are found ubiquitously in nature and are involved in a variety of biological pathways, from natural product synthesis to amino acid and glucose metabolism. The first structure of a PLP-dependent enzyme was reported over 40 years ago, and since that time, there is a steady wealth of structural and functional information revealed for a wide array of these enzymes. A functional mechanism that is gaining more appreciation due to its relevance in drug design is that of protein allostery, where binding of a protein or ligand at a distal site influences the structure, organization, and function at the active site. Here, we present a review of current structure-based mechanisms of allostery for select members of each PLP-dependent enzyme family. Knowledge of these mechanisms may have a larger potential for identifying key similarities and differences among enzyme families that can eventually be exploited for therapeutic development.
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Affiliation(s)
- Jenny U. Tran
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Breann L. Brown
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, United States
- Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, United States
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6
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Ye Y, Fu H, Hyster TK. Activation modes in biocatalytic radical cyclization reactions. J Ind Microbiol Biotechnol 2021; 48:6155068. [PMID: 33674826 PMCID: PMC8210684 DOI: 10.1093/jimb/kuab021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/26/2021] [Indexed: 12/17/2022]
Abstract
Radical cyclizations are essential reactions in the biosynthesis of secondary metabolites and the chemical synthesis of societally valuable molecules. In this review, we highlight the general mechanisms utilized in biocatalytic radical cyclizations. We specifically highlight cytochrome P450 monooxygenases (P450s) involved in the biosynthesis of mycocyclosin and vancomycin, nonheme iron- and α-ketoglutarate-dependent dioxygenases (Fe/αKGDs) used in the biosynthesis of kainic acid, scopolamine, and isopenicillin N, and radical S-adenosylmethionine (SAM) enzymes that facilitate the biosynthesis of oxetanocin A, menaquinone, and F420. Beyond natural mechanisms, we also examine repurposed flavin-dependent “ene”-reductases (ERED) for non-natural radical cyclization. Overall, these general mechanisms underscore the opportunity for enzymes to augment and enhance the synthesis of complex molecules using radical mechanisms.
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Affiliation(s)
- Yuxuan Ye
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Haigen Fu
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Todd K Hyster
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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7
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Hanževački M, Čondić-Jurkić K, Banhatti RD, Smith AS, Smith DM. The Influence of Chemical Change on Protein Dynamics: A Case Study with Pyruvate Formate-Lyase. Chemistry 2019; 25:8741-8753. [PMID: 30901109 DOI: 10.1002/chem.201900663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Indexed: 12/15/2022]
Abstract
Pyruvate formate-lyase (PFL) catalyzes the reversible conversion of pyruvate and coenzyme A (CoA) into formate and acetyl-CoA in two half-reactions. For the second half-reaction to take place, the S-H group of CoA must enter the active site of the enzyme to retrieve a protein-bound acetyl group. However, CoA is bound at the protein surface, whereas the active site is buried in the protein interior, some 20-30 Å away. The PFL system was therefore subjected to a series of extensive molecular dynamics simulations (in the μs range) and a host of advanced analysis procedures. Models representing PFL before and after the first half-reaction were used to examine the possible effect of enzyme acetylation. All simulated structures were found to be relatively stable compared to the initial crystal structure. Although the adenine portion of CoA remained predominantly bound at the protein surface, the binding of the S-H group was significantly more labile. A potential entry channel for CoA, which would allow the S-H group to reach the active site, was identified and characterized. The channel was found to be associated with accentuated fluctuations and a higher probability of being in an open state in acetylated systems. This result suggests that the acetylation of the enzyme assumes a prominent functional role, whereby the formation of the acyl intermediate serves to initiate a subtle signaling cascade that influences the protein dynamics and facilitates the entry of the second substrate.
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Affiliation(s)
- Marko Hanževački
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia.,PULS Group, Institute for Theoretical Physics, FAU Erlangen-Nürnberg, Staudtstraße 7, Erlangen, Germany
| | - Karmen Čondić-Jurkić
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia
| | - Radha Dilip Banhatti
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia
| | - Ana-Sunčana Smith
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia.,PULS Group, Institute for Theoretical Physics, FAU Erlangen-Nürnberg, Staudtstraße 7, Erlangen, Germany
| | - David M Smith
- Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, Zagreb, Croatia
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8
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Han L, Vuksanovic N, Oehm SA, Fenske TG, Schwabacher AW, Silvaggi NR. Streptomyces wadayamensis MppP is a PLP-Dependent Oxidase, Not an Oxygenase. Biochemistry 2018; 57:3252-3264. [DOI: 10.1021/acs.biochem.8b00130] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lanlan Han
- Department of Chemistry and Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Nemanja Vuksanovic
- Department of Chemistry and Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Sarah A. Oehm
- Department of Chemistry and Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Tyler G. Fenske
- Department of Chemistry and Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Alan W. Schwabacher
- Department of Chemistry and Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Nicholas R. Silvaggi
- Department of Chemistry and Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
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9
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Chen JR, Ke SC. Magnetic field effects on coenzyme B12- and B6-dependent lysine 5,6-aminomutase: switching of the J-resonance through a kinetically competent radical-pair intermediate. Phys Chem Chem Phys 2018; 20:13068-13074. [DOI: 10.1039/c8cp01497c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
External magnetic fields interact with lysine 5,6-aminomutase, through an immobilized radical-pair with constant and large exchange interaction, to switch on J-resonance between singlet and triplet spin states, which have different reactive fates.
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Affiliation(s)
- Jun-Ru Chen
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan
| | - Shyue-Chu Ke
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan
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10
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Makins C, Whitelaw DA, McGregor M, Petit A, Mothersole RG, Prosser KE, Wolthers KR. Optimal electrostatic interactions between substrate and protein are essential for radical chemistry in ornithine 4,5-aminomutase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1077-1084. [DOI: 10.1016/j.bbapap.2017.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 05/11/2017] [Accepted: 05/15/2017] [Indexed: 11/17/2022]
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11
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Murugan A, Vidyacharan S, Ghosh R, Sharada DS. Metal-Free Regioselective Dual C-H Functionalization in a Cascade Fashion: Access to Isocryptolepine Alkaloid Analogues. ChemistrySelect 2017. [DOI: 10.1002/slct.201700263] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Arumugavel Murugan
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi Sangareddy-502 285, Telangana INDIA
| | - Shinde Vidyacharan
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi Sangareddy-502 285, Telangana INDIA
| | - Ruma Ghosh
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi Sangareddy-502 285, Telangana INDIA
| | - Duddu S. Sharada
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi Sangareddy-502 285, Telangana INDIA
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12
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The Proteome and Lipidome of Thermococcus kodakarensis across the Stationary Phase. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2016; 2016:5938289. [PMID: 27274708 PMCID: PMC4870337 DOI: 10.1155/2016/5938289] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 04/07/2016] [Indexed: 12/25/2022]
Abstract
The majority of cells in nature probably exist in a stationary-phase-like state, due to nutrient limitation in most environments. Studies on bacteria and yeast reveal morphological and physiological changes throughout the stationary phase, which lead to an increased ability to survive prolonged nutrient limitation. However, there is little information on archaeal stationary phase responses. We investigated protein- and lipid-level changes in Thermococcus kodakarensis with extended time in the stationary phase. Adaptations to time in stationary phase included increased proportion of membrane lipids with a tetraether backbone, synthesis of proteins that ensure translational fidelity, specific regulation of ABC transporters (upregulation of some, downregulation of others), and upregulation of proteins involved in coenzyme production. Given that the biological mechanism of tetraether synthesis is unknown, we also considered whether any of the protein-level changes in T. kodakarensis might shed light on the production of tetraether lipids across the same period. A putative carbon-nitrogen hydrolase, a TldE (a protease in Escherichia coli) homologue, and a membrane bound hydrogenase complex subunit were candidates for possible involvement in tetraether-related reactions, while upregulation of adenosylcobalamin synthesis proteins might lend support to a possible radical mechanism as a trigger for tetraether synthesis.
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13
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Lo HH, Lin HH, Maity AN, Ke SC. The molecular mechanism of the open–closed protein conformational cycle transitions and coupled substrate binding, activation and product release events in lysine 5,6-aminomutase. Chem Commun (Camb) 2016; 52:6399-402. [DOI: 10.1039/c6cc01888b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The contributions of Lys370α and Asp298α to the critical Co–C bond cleavage trigger and open–closed cycle transitions of lysine 5,6-aminomutase.
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Affiliation(s)
- Hsin-Hsi Lo
- Physics Department
- National Dong Hwa University
- Hualien
- Taiwan 97401
| | - Hsin-Hua Lin
- Physics Department
- National Dong Hwa University
- Hualien
- Taiwan 97401
| | | | - Shyue-Chu Ke
- Physics Department
- National Dong Hwa University
- Hualien
- Taiwan 97401
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14
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Maity AN, Lin HH, Chiang HS, Lo HH, Ke SC. Reaction of Pyridoxal-5′-phosphate-N-oxide with Lysine 5,6-Aminomutase: Enzyme Flexibility toward Cofactor Analog. ACS Catal 2015. [DOI: 10.1021/acscatal.5b00671] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
| | - Hsin-Hua Lin
- Department
of Physics, National Dong Hwa University, Hualien, Taiwan 97401
| | | | - Hsin-Hsi Lo
- Department
of Physics, National Dong Hwa University, Hualien, Taiwan 97401
| | - Shyue-Chu Ke
- Department
of Physics, National Dong Hwa University, Hualien, Taiwan 97401
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15
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Maity AN, Ke SC. 4'-CyanoPLP presents better prospect for the experimental detection of elusive cyclic intermediate radical in the reaction of lysine 5,6-aminomutase. Biochem Biophys Res Commun 2015; 457:161-4. [PMID: 25542154 DOI: 10.1016/j.bbrc.2014.12.076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 12/15/2014] [Indexed: 11/26/2022]
Abstract
The results of our calculations suggest that the reaction of 4'-cyanoPLP with lysine 5,6-aminomutase offers better prospect for the experimental detection of elusive cyclic azacyclopropylcarbinyl radical (I), which is proposed to be a key intermediate in the reaction of pyridoxal-5'-phosphate dependent radical aminomutases. We have calculated the corresponding hyperfine coupling constants (HFCCs) for (14)N and (13)C of cyano group using several basis sets to help the characterization of 4'-cyanoI.
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Affiliation(s)
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan.
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16
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Menon BRK, Menon N, Fisher K, Rigby SEJ, Leys D, Scrutton NS. Glutamate 338 is an electrostatic facilitator of C-Co bond breakage in a dynamic/electrostatic model of catalysis by ornithine aminomutase. FEBS J 2015; 282:1242-55. [PMID: 25627283 PMCID: PMC4413051 DOI: 10.1111/febs.13215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 01/16/2015] [Accepted: 01/23/2015] [Indexed: 01/04/2023]
Abstract
How cobalamin-dependent enzymes promote C–Co homolysis to initiate radical catalysis has been debated extensively. For the pyridoxal 5′-phosphate and cobalamin-dependent enzymes lysine 5,6-aminomutase and ornithine 4,5-aminomutase (OAM), large-scale re-orientation of the cobalamin-binding domain linked to C–Co bond breakage has been proposed. In these models, substrate binding triggers dynamic sampling of the B12-binding Rossmann domain to achieve a catalytically competent ‘closed’ conformational state. In ‘closed’ conformations of OAM, Glu338 is thought to facilitate C–Co bond breakage by close association with the cobalamin adenosyl group. We investigated this using stopped-flow continuous-wave photolysis, viscosity dependence kinetic measurements, and electron paramagnetic resonance spectroscopy of a series of Glu338 variants. We found that substrate-induced C–Co bond homolysis is compromised in Glu388 variant forms of OAM, although photolysis of the C–Co bond is not affected by the identity of residue 338. Electrostatic interactions of Glu338 with the 5′-deoxyadenosyl group of B12 potentiate C–Co bond homolysis in ‘closed’ conformations only; these conformations are unlocked by substrate binding. Our studies extend earlier models that identified a requirement for large-scale motion of the cobalamin domain. Our findings indicate that large-scale motion is required to pre-organize the active site by enabling transient formation of ‘closed’ conformations of OAM. In ‘closed’ conformations, Glu338 interacts with the 5′-deoxyadenosyl group of cobalamin. This interaction is required to potentiate C–Co homolysis, and is a crucial component of the approximately 1012 rate enhancement achieved by cobalamin-dependent enzymes for C–Co bond homolysis.
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Affiliation(s)
- Binuraj R K Menon
- Biotechnology and Biological Sciences Research Council/Engineering and Physical Sciences Research Council Centre for Synthetic Biology of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, UK
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17
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Menon BRK, Fisher K, Rigby SEJ, Scrutton NS, Leys D. A conformational sampling model for radical catalysis in pyridoxal phosphate- and cobalamin-dependent enzymes. J Biol Chem 2014; 289:34161-74. [PMID: 25213862 PMCID: PMC4256349 DOI: 10.1074/jbc.m114.590471] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cobalamin-dependent enzymes enhance the rate of C–Co bond cleavage by up to ∼1012-fold to generate cob(II)alamin and a transient adenosyl radical. In the case of the pyridoxal 5′-phosphate (PLP) and cobalamin-dependent enzymes lysine 5,6-aminomutase and ornithine 4,5 aminomutase (OAM), it has been proposed that a large scale domain reorientation of the cobalamin-binding domain is linked to radical catalysis. Here, OAM variants were designed to perturb the interface between the cobalamin-binding domain and the PLP-binding TIM barrel domain. Steady-state and single turnover kinetic studies of these variants, combined with pulsed electron-electron double resonance measurements of spin-labeled OAM were used to provide direct evidence for a dynamic interface between the cobalamin and PLP-binding domains. Our data suggest that following ligand binding-induced cleavage of the Lys629-PLP covalent bond, dynamic motion of the cobalamin-binding domain leads to conformational sampling of the available space. This supports radical catalysis through transient formation of a catalytically competent active state. Crucially, it appears that the formation of the state containing both a substrate/product radical and Co(II) does not restrict cobalamin domain motion. A similar conformational sampling mechanism has been proposed to support rapid electron transfer in a number of dynamic redox systems.
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Affiliation(s)
- Binuraj R K Menon
- From the Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Karl Fisher
- From the Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Stephen E J Rigby
- From the Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Nigel S Scrutton
- From the Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - David Leys
- From the Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester M1 7DN, United Kingdom
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18
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Makins C, Whitelaw DA, Mu C, Walsby CJ, Wolthers KR. Isotope effects for deuterium transfer and mutagenesis of Tyr187 provide insight into controlled radical chemistry in adenosylcobalamin-dependent ornithine 4,5-aminomutase. Biochemistry 2014; 53:5432-43. [PMID: 25100213 DOI: 10.1021/bi5006706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Adenosylcobalamin-dependent ornithine 4,5-aminomutase (OAM) from Clostridium sticklandii utilizes pyridoxal 5'-phosphate (PLP) to interconvert d-ornithine to 2,4-diaminopentanoate via a multistep mechanism that involves two hydrogen transfer steps. Herein, we uncover features of the OAM catalytic mechanism that differentiate it from its homologue, the more catalytically promiscuous lysine 5,6-aminomutase. Kinetic isotope effects (KIEs) with dl-ornithine-3,3,4,4,5,5-d6 revealed a diminished (D)kcat/Km of 2.5 ± 0.4 relative to a (D)kcat of 7.6 ± 0.5, suggesting slow release of the substrate from the active site. In contrast, a KIE was not observed on the rate constant associated with Co-C bond homolysis as this step is likely "gated" by the formation of the external aldimine. The role of tyrosine 187, which lies planar to the PLP pyridine ring, was also investigated via site-directed mutagenesis. The 25- and 1260-fold reduced kcat values for Y187F and Y187A, respectively, are attributed to a slower rate of external aldimine formation and a diminution of adenosylcobalamin Co-C bond homolysis. Notably, electron paramagnetic resonance studies of Y187F suggest that the integrity of the active site is maintained as cob(II)alamin and the PLP organic radical (even at lower concentrations) remain tightly exchange-coupled. Modeling of d-lysine and l-β-lysine into the 5,6-LAM active site reveals interactions between the substrate and protein are weaker than those in OAM and fewer in number. The combined data suggest that the level of protein-substrate interactions in aminomutases not only influences substrate specificity, but also controls radical chemistry.
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Affiliation(s)
- Caitlyn Makins
- Department of Chemistry, University of British Columbia , 3333 University Way, Kelowna, BC V1V 1V7, Canada
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Pang J, Scrutton NS, Sutcliffe MJ. Quantum Mechanics/Molecular Mechanics Studies on the Mechanism of Action of Cofactor Pyridoxal 5′-Phosphate in Ornithine 4,5-Aminomutase. Chemistry 2014; 20:11390-401. [DOI: 10.1002/chem.201402759] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Indexed: 02/02/2023]
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Callebaut G, Meiresonne T, De Kimpe N, Mangelinckx S. Synthesis and Reactivity of 2-(Carboxymethyl)aziridine Derivatives. Chem Rev 2014; 114:7954-8015. [DOI: 10.1021/cr400582d] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Gert Callebaut
- Department of Sustainable
Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
| | - Tamara Meiresonne
- Department of Sustainable
Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
| | - Norbert De Kimpe
- Department of Sustainable
Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
| | - Sven Mangelinckx
- Department of Sustainable
Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
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Maity AN, Chen YH, Ke SC. Large-scale domain motions and pyridoxal-5'-phosphate assisted radical catalysis in coenzyme B12-dependent aminomutases. Int J Mol Sci 2014; 15:3064-87. [PMID: 24562332 PMCID: PMC3958899 DOI: 10.3390/ijms15023064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 12/25/2013] [Accepted: 01/22/2014] [Indexed: 12/31/2022] Open
Abstract
Lysine 5,6-aminomutase (5,6-LAM) and ornithine 4,5-aminomutase (4,5-OAM) are two of the rare enzymes that use assistance of two vitamins as cofactors. These enzymes employ radical generating capability of coenzyme B12 (5'-deoxyadenosylcobalamin, dAdoCbl) and ability of pyridoxal-5'-phosphate (PLP, vitamin B6) to stabilize high-energy intermediates for performing challenging 1,2-amino rearrangements between adjacent carbons. A large-scale domain movement is required for interconversion between the catalytically inactive open form and the catalytically active closed form. In spite of all the similarities, these enzymes differ in substrate specificities. 4,5-OAM is highly specific for D-ornithine as a substrate while 5,6-LAM can accept D-lysine and L-β-lysine. This review focuses on recent computational, spectroscopic and structural studies of these enzymes and their implications on the related enzymes. Additionally, we also discuss the potential biosynthetic application of 5,6-LAM.
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Affiliation(s)
| | - Yung-Han Chen
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan.
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan.
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22
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Juzeniene A, Nizauskaite Z. Photodegradation of cobalamins in aqueous solutions and in human blood. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2013; 122:7-14. [PMID: 23558034 DOI: 10.1016/j.jphotobiol.2013.03.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/26/2013] [Accepted: 03/01/2013] [Indexed: 01/14/2023]
Abstract
Vitamin B12 (cobalamin) is required for proper red blood cell formation, neurologic function, and DNA synthesis. Cobalamins in solutions are light sensitive, but no comprehensive study has been performed to compare the photostability of different cobalamins under UVA exposure. Their indirect photodegradation due to their antioxidant properties and their photostability in vivo have also not been studied so far. The photodegradation of four cobalamins (methylcobalamin (MeCbl), adenosylcobalamin (AdCbl), hydroxocobalamin (OHCbl) and cyanocobalamin (CNCbl)) under UVA exposure in aqueous solutions (pH=7.4) have been investigated by absorption spectroscopy. The photodegradation of OHCbl in the absence and presence of the endogenous photosensitizer riboflavin was studied. Serum vitamin B12 concentrations before and after summer were measured in four patients with psoriasis. All studied cobalamins are photolabile. The biologically active forms of cobalamin, AdCbl and MeCbl, are converted to OHCbl within seconds during UVA exposure. OHCbl is the most stable cobalamin. However, reactive oxygen species increases the degradation rate of OHCbl. Our pilot study on humans demonstrates that serum vitamin B12 concentrations are not significantly affected during summertime in Norway. Further work is needed to determine vitamin B12 photostability in humans living at lower latitudes or using sunbeds.
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Affiliation(s)
- Asta Juzeniene
- Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Montebello, N-0310 Oslo, Norway.
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Makins C, Pickering AV, Mariani C, Wolthers KR. Mutagenesis of a conserved glutamate reveals the contribution of electrostatic energy to adenosylcobalamin co-C bond homolysis in ornithine 4,5-aminomutase and methylmalonyl-CoA mutase. Biochemistry 2013; 52:878-88. [PMID: 23311430 DOI: 10.1021/bi3012719] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Binding of substrate to ornithine 4,5-aminomutase (OAM) and methylmalonyl-CoA mutase (MCM) leads to the formation of an electrostatic interaction between a conserved glutamate side chain and the adenosyl ribose of the adenosylcobalamin (AdoCbl) cofactor. The contribution of this residue (Glu338 in OAM from Clostridium sticklandii and Glu392 in human MCM) to AdoCbl Co-C bond labilization and catalysis was evaluated by substituting the residue with a glutamine, aspartate, or alanine. The OAM variants, E338Q, E338D, and E338A, showed 90-, 380-, and 670-fold reductions in catalytic turnover and 20-, 60-, and 220-fold reductions in k(cat)/K(m), respectively. Likewise, the MCM variants, E392Q, E392D, and E392A, showed 16-, 330-, and 12-fold reductions in k(cat), respectively. Binding of substrate to OAM is unaffected by the single-amino acid mutation as stopped-flow absorbance spectroscopy showed that the rates of external aldimine formation in the OAM variants were similar to that of the native enzyme. The decrease in the level of catalysis is instead linked to impaired Co-C bond rupture, as UV-visible spectroscopy did not show detectable AdoCbl homolysis upon binding of the physiological substrate, d-ornithine. AdoCbl homolysis was also not detected in the MCM mutants, as it was for the native enzyme. We conclude from these results that a gradual weakening of the electrostatic energy between the protein and the ribose leads to a progressive increase in the activation energy barrier for Co-C bond homolysis, thereby pointing to a key role for the conserved polar glutamate residue in controlling the initial generation of radical species.
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Affiliation(s)
- Caitlyn Makins
- Department of Chemistry, University of British Columbia, 3333 University Way, Kelowna, BC, Canada
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Adenosylcobalamin enzymes: theory and experiment begin to converge. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1154-64. [PMID: 22516318 DOI: 10.1016/j.bbapap.2012.03.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 02/04/2012] [Accepted: 03/27/2012] [Indexed: 11/21/2022]
Abstract
Adenosylcobalamin (coenzyme B(12)) serves as the cofactor for a group of enzymes that catalyze unusual rearrangement or elimination reactions. The role of the cofactor as the initiator of reactive free radicals needed for these reactions is well established. Less clear is how these enzymes activate the coenzyme towards homolysis and control the radicals once generated. The availability of high resolution X-ray structures combined with detailed kinetic and spectroscopic analyses have allowed several adenosylcobalamin enzymes to be computationally modeled in some detail. Computer simulations have generally obtained good agreement with experimental data and provided valuable insight into the mechanisms of these unusual reactions. Importantly, atomistic modeling of the enzymes has allowed the role of specific interactions between protein, substrate and coenzyme to be explored, leading to mechanistic predictions that can now be tested experimentally. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology.
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Makins C, Miros FN, Scrutton NS, Wolthers KR. Role of histidine 225 in adenosylcobalamin-dependent ornithine 4,5-aminomutase. Bioorg Chem 2012; 40:39-47. [DOI: 10.1016/j.bioorg.2011.08.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 08/05/2011] [Accepted: 08/08/2011] [Indexed: 12/01/2022]
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Pang J, Li X, Morokuma K, Scrutton NS, Sutcliffe MJ. Large-Scale Domain Conformational Change Is Coupled to the Activation of the Co–C Bond in the B12-Dependent Enzyme Ornithine 4,5-Aminomutase: A Computational Study. J Am Chem Soc 2012; 134:2367-77. [DOI: 10.1021/ja210417k] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
| | - Xin Li
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
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Wu B, Szymański W, Heberling MM, Feringa BL, Janssen DB. Aminomutases: mechanistic diversity, biotechnological applications and future perspectives. Trends Biotechnol 2011; 29:352-62. [PMID: 21477876 DOI: 10.1016/j.tibtech.2011.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/22/2011] [Accepted: 02/23/2011] [Indexed: 11/26/2022]
Abstract
Aminomutases carry out the chemically challenging exchange of a hydrogen atom and an amine substituent present on neighboring carbon atoms. In recent years, aminomutases have been intensively investigated for their biophysical, structural and mechanistic characteristics. The reactions catalyzed by these enzymes have considerable potential for biotechnological applications. Here, we present an overview of this diverse group of enzymes, with a focus on enzymatic mechanisms and recent developments in their use in applied biocatalysis.
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Affiliation(s)
- Bian Wu
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Wolthers KR, Levy C, Scrutton NS, Leys D. Large-scale domain dynamics and adenosylcobalamin reorientation orchestrate radical catalysis in ornithine 4,5-aminomutase. J Biol Chem 2010; 285:13942-50. [PMID: 20106986 PMCID: PMC2859556 DOI: 10.1074/jbc.m109.068908] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 11/16/2009] [Indexed: 11/06/2022] Open
Abstract
D-ornithine 4,5-aminomutase (OAM) from Clostridium sticklandii converts D-ornithine to 2,4-diaminopentanoic acid by way of radical propagation from an adenosylcobalamin (AdoCbl) to a pyridoxal 5'-phosphate (PLP) cofactor. We have solved OAM crystal structures in different catalytic states that together demonstrate unusual stability of the AdoCbl Co-C bond and that radical catalysis is coupled to large-scale domain motion. The 2.0-A substrate-free enzyme crystal structure reveals the Rossmann domain, harboring the intact AdoCbl cofactor, is tilted toward the edge of the PLP binding triose-phosphate isomerase barrel domain. The PLP forms an internal aldimine link to the Rossmann domain through Lys(629), effectively locking the enzyme in this "open" pre-catalytic conformation. The distance between PLP and 5'-deoxyadenosyl group is 23 A, and large-scale domain movement is thus required prior to radical catalysis. The OAM crystals contain two Rossmann domains within the asymmetric unit that are unconstrained by the crystal lattice. Surprisingly, the binding of various ligands to OAM crystals (in an oxygen-free environment) leads to transimination in the absence of significant reorientation of the Rossmann domains. In contrast, when performed under aerobic conditions, this leads to extreme disorder in the latter domains correlated with the loss of the 5'-deoxyadenosyl group. Our data indicate turnover and hence formation of the "closed" conformation is occurring within OAM crystals, but that the equilibrium is poised toward the open conformation. We propose that substrate binding induces large-scale domain motion concomitant with a reconfiguration of the 5'-deoxyadenosyl group, triggering radical catalysis in OAM.
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Affiliation(s)
- Kirsten R. Wolthers
- From the Faculty of Life Sciences, University of Manchester, Manchester Interdisciplinary Biocentre, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Colin Levy
- From the Faculty of Life Sciences, University of Manchester, Manchester Interdisciplinary Biocentre, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Nigel S. Scrutton
- From the Faculty of Life Sciences, University of Manchester, Manchester Interdisciplinary Biocentre, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - David Leys
- From the Faculty of Life Sciences, University of Manchester, Manchester Interdisciplinary Biocentre, 131 Princess Street, Manchester M1 7DN, United Kingdom
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Tang KH, Mansoorabadi SO, Reed GH, Frey PA. Radical triplets and suicide inhibition in reactions of 4-thia-D- and 4-thia-L-lysine with lysine 5,6-aminomutase. Biochemistry 2009; 48:8151-60. [PMID: 19634897 DOI: 10.1021/bi900828f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lysine 5,6-aminomutase (5,6-LAM) catalyzes the interconversions of D- or L-lysine and the corresponding enantiomers of 2,5-diaminohexanoate, as well as the interconversion of L-beta-lysine and l-3,5-diaminohexanoate. The reactions of 5,6-LAM are 5'-deoxyadenosylcobalamin- and pyridoxal-5'-phosphate (PLP)-dependent. Similar to other 5'-deoxyadenosylcobalamin-dependent enzymes, 5,6-LAM is thought to function by a radical mechanism. No free radicals can be detected by electron paramagnetic resonance (EPR) spectroscopy in reactions of 5,6-LAM with D- or L-lysine or with L-beta-lysine. However, the substrate analogues 4-thia-L-lysine and 4-thia-D-lysine undergo early steps in the mechanism to form two radical species that are readily detected by EPR spectroscopy. Cob(II)alamin and 5'-deoxyadenosine derived from 5'-deoxyadenosylcobalamin are also detected. The radicals are proximal to and spin-coupled with low-spin Co(2+) in cob(II)alamin and appear as radical triplets. The radicals are reversibly formed but do not proceed to stable products, so that 4-thia-D- and L-lysine are suicide inhibitors. Inhibition attains equilibrium between the active Michaelis complex and the inhibited radical triplets. The structure of the transient 4-thia-L-lysine radical is analogous to that of the first substrate-related radical in the putative isomerization mechanism. The second, persistent radical is more stable than the transient species and is assigned as a tautomer, in which a C6(H) of the transient radical is transferred to the carboxaldehyde carbon (C4') of PLP. The persistent radical blocks the active site and inhibits the enzyme, but it decomposes very slowly at </=1% of the rate of formation to regenerate the active enzyme. Fundamental differences between reversible suicide inactivation by 4-thia-D- or L-4-lysine and irreversible suicide inactivation by D- or L-lysine are discussed. The observation of the transient radical supports the hypothetical isomerization mechanism.
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Affiliation(s)
- Kuo-Hsiang Tang
- Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, Madison, Wisconsin 53726, USA
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