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Peñalver M, Paradela A, Palacios-Cuéllar C, Pucciarelli MG, García-Del Portillo F. Experimental evidence of d-glutamate racemase activity in the uncultivated bacterium Candidatus Saccharimonas aalborgensis. Environ Microbiol 2024; 26:e16621. [PMID: 38558504 DOI: 10.1111/1462-2920.16621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 03/16/2024] [Indexed: 04/04/2024]
Abstract
The Candidate Phyla Radiation (CPR) encompasses widespread uncultivated bacteria with reduced genomes and limited metabolic capacities. Most CPR bacteria lack the minimal set of enzymes required for peptidoglycan (PG) synthesis, leaving it unclear how these bacteria produce this essential envelope component. In this study, we analysed the distribution of d-amino acid racemases that produce the universal PG components d-glutamate (d-Glu) or d-alanine (d-Ala). We also examined moonlighting enzymes that synthesize d-Glu or d-Ala. Unlike other phyla in the domain Bacteria, CPR bacteria do not exhibit these moonlighting activities and have, at most, one gene encoding either a Glu or Ala racemase. One of these 'orphan' racemases is a predicted Glu racemase (MurICPR) from the CPR bacterium Candidatus Saccharimonas aalborgenesis. The expression of MurICPR restores the growth of a Salmonella d-Glu auxotroph lacking its endogenous racemase and results in the substitution of l-Ala by serine as the first residue in a fraction of the PG stem peptides. In vitro, MurICPR exclusively racemizes Glu as a substrate. Therefore, Ca. Saccharimonas aalborgensis may couple Glu racemization to serine and d-Glu incorporation into the stem peptide. Our findings provide the first insights into the synthesis of PG by an uncultivated environmental bacterium and illustrate how to experimentally test enzymatic activities from CPR bacteria related to PG metabolism.
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Affiliation(s)
- Marcos Peñalver
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid (UAM), Madrid, Spain
- Centro de Biologia Molecular Severo Ochoa (CBM), CSIC-UAM, Madrid, Spain
| | - Alberto Paradela
- Proteomics Facility, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
| | - César Palacios-Cuéllar
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
| | - M Graciela Pucciarelli
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid (UAM), Madrid, Spain
- Centro de Biologia Molecular Severo Ochoa (CBM), CSIC-UAM, Madrid, Spain
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2
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Bearne SL. Design and evaluation of substrate-product analog inhibitors for racemases and epimerases utilizing a 1,1-proton transfer mechanism. Methods Enzymol 2023; 690:397-444. [PMID: 37858537 DOI: 10.1016/bs.mie.2023.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
Racemases and epimerases catalyze the inversion of stereochemistry at asymmetric carbon atoms to generate stereoisomers that often play important roles in normal and pathological physiology. Consequently, there is interest in developing inhibitors of these enzymes for drug discovery. A strategy for the rational design of substrate-product analog (SPA) inhibitors of racemases and epimerases utilizing a direct 1,1-proton transfer mechanism is elaborated. This strategy assumes that two groups on the asymmetric carbon atom remain fixed at active-site binding determinants, while the hydrogen and third, motile group move during catalysis, with the latter potentially traveling between an R- and S-pocket at the active site. SPAs incorporate structural features of the substrate and product, often with geminal disubstitution on the asymmetric carbon atom to simultaneously present the motile group to both the R- and S-pockets. For racemases operating on substrates bearing three polar groups (glutamate, aspartate, and serine racemases) or with compact, hydrophobic binding pockets (proline racemase), substituent motion is limited and the design strategy furnishes inhibitors with poor or modest binding affinities. The approach is most successful when substrates have a large, motile hydrophobic group that binds at a plastic and/or capacious hydrophobic site. Potent inhibitors were developed for mandelate racemase, isoleucine epimerase, and α-methylacyl-CoA racemase using the SPA inhibitor design strategy, exhibiting binding affinities ranging from substrate-like to exceeding that of the substrate by 100-fold. This rational approach for designing inhibitors of racemases and epimerases having the appropriate active-site architectures is a useful strategy for furnishing compounds for drug development.
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Affiliation(s)
- Stephen L Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada; Department of Chemistry, Dalhousie University, Halifax, NS, Canada.
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3
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Deletti G, Green SD, Weber C, Patterson KN, Joshi SS, Khopade TM, Coban M, Veek-Wilson J, Caulfield TR, Viswanathan R, Lane AL. Unveiling an indole alkaloid diketopiperazine biosynthetic pathway that features a unique stereoisomerase and multifunctional methyltransferase. Nat Commun 2023; 14:2558. [PMID: 37137876 PMCID: PMC10156859 DOI: 10.1038/s41467-023-38168-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 04/19/2023] [Indexed: 05/05/2023] Open
Abstract
The 2,5-diketopiperazines are a prominent class of bioactive molecules. The nocardioazines are actinomycete natural products that feature a pyrroloindoline diketopiperazine scaffold composed of two D-tryptophan residues functionalized by N- and C-methylation, prenylation, and diannulation. Here we identify and characterize the nocardioazine B biosynthetic pathway from marine Nocardiopsis sp. CMB-M0232 by using heterologous biotransformations, in vitro biochemical assays, and macromolecular modeling. Assembly of the cyclo-L-Trp-L-Trp diketopiperazine precursor is catalyzed by a cyclodipeptide synthase. A separate genomic locus encodes tailoring of this precursor and includes an aspartate/glutamate racemase homolog as an unusual D/L isomerase acting upon diketopiperazine substrates, a phytoene synthase-like prenyltransferase as the catalyst of indole alkaloid diketopiperazine prenylation, and a rare dual function methyltransferase as the catalyst of both N- and C-methylation as the final steps of nocardioazine B biosynthesis. The biosynthetic paradigms revealed herein showcase Nature's molecular ingenuity and lay the foundation for diketopiperazine diversification via biocatalytic approaches.
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Affiliation(s)
- Garrett Deletti
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Sajan D Green
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Caleb Weber
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Kristen N Patterson
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA
| | - Swapnil S Joshi
- Departments of Chemistry & Biology, Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India
| | - Tushar M Khopade
- Departments of Chemistry & Biology, Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India
| | - Mathew Coban
- Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - James Veek-Wilson
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA
| | - Thomas R Caulfield
- Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, 32224, USA
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | - Rajesh Viswanathan
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA.
- Departments of Chemistry & Biology, Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India.
| | - Amy L Lane
- Department of Chemistry & Biochemistry, University of North Florida, Jacksonville, FL, 32224, USA.
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4
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Caldwell M, Hughes M, Wei F, Ngo C, Pascua R, Pugazhendhi AS, Coathup MJ. Promising applications of D-amino acids in periprosthetic joint infection. Bone Res 2023; 11:14. [PMID: 36894568 PMCID: PMC9998894 DOI: 10.1038/s41413-023-00254-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/02/2023] [Accepted: 02/10/2023] [Indexed: 03/11/2023] Open
Abstract
Due to the rise in our aging population, a disproportionate demand for total joint arthroplasty (TJA) in the elderly is forecast. Periprosthetic joint infection (PJI) represents one of the most challenging complications that can occur following TJA, and as the number of primary and revision TJAs continues to rise, an increasing PJI burden is projected. Despite advances in operating room sterility, antiseptic protocols, and surgical techniques, approaches to prevent and treat PJI remain difficult, primarily due to the formation of microbial biofilms. This difficulty motivates researchers to continue searching for an effective antimicrobial strategy. The dextrorotatory-isoforms of amino acids (D-AAs) are essential components of peptidoglycan within the bacterial cell wall, providing strength and structural integrity in a diverse range of species. Among many tasks, D-AAs regulate cell morphology, spore germination, and bacterial survival, evasion, subversion, and adhesion in the host immune system. When administered exogenously, accumulating data have demonstrated that D-AAs play a pivotal role against bacterial adhesion to abiotic surfaces and subsequent biofilm formation; furthermore, D-AAs have substantial efficacy in promoting biofilm disassembly. This presents D-AAs as promising and novel targets for future therapeutic approaches. Despite their emerging antibacterial efficacy, their role in disrupting PJI biofilm formation, the disassembly of established TJA biofilm, and the host bone tissue response remains largely unexplored. This review aims to examine the role of D-AAs in the context of TJAs. Data to date suggest that D-AA bioengineering may serve as a promising future strategy in the prevention and treatment of PJI.
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Affiliation(s)
- Matthew Caldwell
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Megan Hughes
- School of Biosciences, Cardiff University, CF10 3AT, Wales, UK
| | - Fei Wei
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Christopher Ngo
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Raven Pascua
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Abinaya Sindu Pugazhendhi
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA
| | - Melanie J Coathup
- Biionix Cluster & College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA.
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5
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Ji R, Shen J. Chirality Transformation in Metathesis Reactions of Salicylaldehyde/Pyridoxal‐Based Imines. ChemistrySelect 2022. [DOI: 10.1002/slct.202201332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Rui‐Xue Ji
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing College of Materials Science and Engineering Huaqiao University Xiamen 361021 China
| | - Jiang‐Shan Shen
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing College of Materials Science and Engineering Huaqiao University Xiamen 361021 China
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6
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Oda K, Sakaguchi T, Matoba Y. Crystal structure of O-ureidoserine racemase found in the d-cycloserine biosynthetic pathway. Proteins 2021; 90:912-918. [PMID: 34877716 DOI: 10.1002/prot.26290] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/22/2021] [Accepted: 12/02/2021] [Indexed: 01/03/2023]
Abstract
The O-ureidoserine racemase (DcsC) is an enzyme found from the biosynthetic gene cluster of antitubercular agent d-cycloserine. Although DcsC is homologous to diaminopimelate epimerase (DapF) that catalyzes the interconversion between ll- and dl-diaminopimelic acid, it specifically catalyzes the interconversion between O-ureido-l-serine and its enantiomer. Here we determined the crystal structure of DcsC at a resolution of 2.12 Å, implicating that the catalytic mechanism of DcsC shares similarity with that of DapF. Comparing the structure of the active center of DcsC to that of DapF, Thr72, Thr198, and Tyr219 of DcsC are likely to be involved in the substrate specificity.
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Affiliation(s)
- Kosuke Oda
- Department of Virology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Takemasa Sakaguchi
- Department of Virology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Yasuyuki Matoba
- Faculty of Pharmacy, Yasuda Women's University, Hiroshima, Japan
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7
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Abstract
Although dynamic reactions of imines have been extensively studied, the dynamic behaviors manipulated by chirality remain nearly unexplored. In this work, enantioselective amine exchange reactions were demonstrated as a first example via the reaction of enantiomeric chiral amines such as natural amino acids with a series of innovative axially chiral 1,1'-binaphthyl-2,2'-diamine (BNDA)-based imines that were prepared from the condensation reactions between BNDA and salicylaldehyde (SA) or its derivatives. This enantioselective dynamic behavior can be directly indicated by the degree of the fluorescence response of the R-configuration of imines to the d-enantiomer of chiral amine, because the released BNDA can serve as the fluorescence signal output when the amine exchange reaction occurs, which is far higher than the response to its l-enantiomer under identical experimental conditions. For the S-configuration of chiral imines, the fluorescence response is the opposite. The enantioselective exchange reaction can be tuned by altering the electron-withdrawing or electron-donating capability of the substituent at position 4 or 5 of the SA part of chiral imines. Not only o-OH groups in SA-based imines but also protic solvents used as reaction media were found to be important to the dynamic behavior at high rates.
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Affiliation(s)
- Rui-Xue Ji
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China
| | - Ning Liu
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China
| | - Jiang-Shan Shen
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China
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8
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Yamanaka K, Ozaki R, Hamano Y, Oikawa T. Molecular and Mechanistic Characterization of PddB, the First PLP-Independent 2,4-Diaminobutyric Acid Racemase Discovered in an Actinobacterial D-Amino Acid Homopolymer Biosynthesis. Front Microbiol 2021; 12:686023. [PMID: 34177872 PMCID: PMC8225329 DOI: 10.3389/fmicb.2021.686023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 05/13/2021] [Indexed: 11/13/2022] Open
Abstract
We recently disclosed that the biosynthesis of antiviral γ-poly-D-2,4-diaminobutyric acid (poly-D-Dab) in Streptoalloteichus hindustanus involves an unprecedented cofactor independent stereoinversion of Dab catalyzed by PddB, which shows weak homology to diaminopimelate epimerase (DapF). Enzymological properties and mechanistic details of this enzyme, however, had remained to be elucidated. Here, through a series of biochemical characterizations, structural modeling, and site-directed mutageneses, we fully illustrate the first Dab-specific PLP-independent racemase PddB and further provide an insight into its evolution. The activity of the recombinant PddB was shown to be optimal around pH 8.5, and its other fundamental properties resembled those of typical PLP-independent racemases/epimerases. The enzyme catalyzed Dab specific stereoinversion with a calculated equilibrium constant of nearly unity, demonstrating that the reaction catalyzed by PddB is indeed racemization. Its activity was inhibited upon incubation with sulfhydryl reagents, and the site-directed substitution of two putative catalytic Cys residues led to the abolishment of the activity. These observations provided critical evidence that PddB employs the thiolate-thiol pair to catalyze interconversion of Dab isomers. Despite the low levels of sequence similarity, a phylogenetic analysis of PddB indicated its particular relevance to DapF among PLP-independent racemases/epimerases. Secondary structure prediction and 3D structural modeling of PddB revealed its remarkable conformational analogy to DapF, which in turn allowed us to predict amino acid residues potentially responsible for the discrimination of structural difference between diaminopimelate and its specific substrate, Dab. Further, PddB homologs which seemed to be narrowly distributed only in actinobacterial kingdom were constantly encoded adjacent to the putative poly-D-Dab synthetase gene. These observations strongly suggested that PddB could have evolved from the primary metabolic DapF in order to organize the biosynthesis pathway for the particular secondary metabolite, poly-D-Dab. The present study is on the first molecular characterization of PLP-independent Dab racemase and provides insights that could contribute to further discovery of unprecedented PLP-independent racemases.
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Affiliation(s)
- Kazuya Yamanaka
- Department of Life Science and Technology, Faculty of Chemistry, Materials, and Bioengineering, Kansai University, Suita, Japan.,Graduate School of Science and Engineering, Kansai University, Suita, Japan
| | - Ryo Ozaki
- Graduate School of Science and Engineering, Kansai University, Suita, Japan
| | - Yoshimitsu Hamano
- Department of Bioscience, Faculty of Biotechnology, Fukui Prefectural University, Yoshida-gun, Japan
| | - Tadao Oikawa
- Department of Life Science and Technology, Faculty of Chemistry, Materials, and Bioengineering, Kansai University, Suita, Japan.,Graduate School of Science and Engineering, Kansai University, Suita, Japan
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9
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Lloyd MD, Yevglevskis M, Nathubhai A, James TD, Threadgill MD, Woodman TJ. Racemases and epimerases operating through a 1,1-proton transfer mechanism: reactivity, mechanism and inhibition. Chem Soc Rev 2021; 50:5952-5984. [PMID: 34027955 PMCID: PMC8142540 DOI: 10.1039/d0cs00540a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Indexed: 12/12/2022]
Abstract
Racemases and epimerases catalyse changes in the stereochemical configurations of chiral centres and are of interest as model enzymes and as biotechnological tools. They also occupy pivotal positions within metabolic pathways and, hence, many of them are important drug targets. This review summarises the catalytic mechanisms of PLP-dependent, enolase family and cofactor-independent racemases and epimerases operating by a deprotonation/reprotonation (1,1-proton transfer) mechanism and methods for measuring their catalytic activity. Strategies for inhibiting these enzymes are reviewed, as are specific examples of inhibitors. Rational design of inhibitors based on substrates has been extensively explored but there is considerable scope for development of transition-state mimics and covalent inhibitors and for the identification of inhibitors by high-throughput, fragment and virtual screening approaches. The increasing availability of enzyme structures obtained using X-ray crystallography will facilitate development of inhibitors by rational design and fragment screening, whilst protein models will facilitate development of transition-state mimics.
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Affiliation(s)
- Matthew D Lloyd
- Drug & Target Discovery, Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK.
| | - Maksims Yevglevskis
- Drug & Target Discovery, Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK. and CatSci Ltd., CBTC2, Capital Business Park, Wentloog, Cardiff CF3 2PX, UK
| | - Amit Nathubhai
- Drug & Target Discovery, Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK. and University of Sunderland, School of Pharmacy & Pharmaceutical Sciences, Sciences Complex, Sunderland SR1 3SD, UK
| | - Tony D James
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK and School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, People's Republic of China
| | - Michael D Threadgill
- Drug & Target Discovery, Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK. and Institute of Biological, Environmental & Rural Sciences, Aberystwyth University, Aberystwyth SY23 3BY, UK
| | - Timothy J Woodman
- Drug & Target Discovery, Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK.
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10
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TK1211 Encodes an Amino Acid Racemase towards Leucine and Methionine in the Hyperthermophilic Archaeon Thermococcus kodakarensis. J Bacteriol 2021; 203:JB.00617-20. [PMID: 33468590 DOI: 10.1128/jb.00617-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 01/07/2021] [Indexed: 12/22/2022] Open
Abstract
Members of Thermococcales harbor a number of genes encoding putative aminotransferase class III enzymes. Here, we characterized the TK1211 protein from the hyperthermophilic archaeon Thermococcus kodakarensis The TK1211 gene was expressed in T. kodakarensis under the control of the strong, constitutive promoter of the cell surface glycoprotein gene TK0895 (P csg ). The purified protein did not display aminotransferase activity but exhibited racemase activity. An examination of most amino acids indicated that the enzyme was a racemase with relatively high activity toward Leu and Met. Kinetic analysis indicated that Leu was the most preferred substrate. A TK1211 gene disruption strain (ΔTK1211) was constructed and grown on minimal medium supplemented with l- or d-Leu or l- or d-Met. The wild-type T. kodakarensis is not able to synthesize Leu and displays Leu auxotrophy, providing a direct means to examine the Leu racemase activity of the TK1211 protein in vivo When we replaced l-Leu with d-Leu in the medium, the host strain with an intact TK1211 gene displayed an extended lag phase but displayed cell yield similar to that observed in medium with l-Leu. In contrast, the ΔTK1211 strain displayed growth in medium with l-Leu but could not grow with d-Leu. The results indicate that TK1211 encodes a Leu racemase that is active in T. kodakarensis cells and that no other protein exhibits this activity, at least to an extent that can support growth. Growth experiments with l- or d-Met also confirmed the Met racemase activity of the TK1211 protein in T. kodakarensis IMPORTANCE Phylogenetic analysis of aminotransferase class III proteins from all domains of life reveals numerous groups of protein sequences. One of these groups includes a large number of sequences from Thermococcales species and can be divided into four subgroups. Representatives of three of these subgroups have been characterized in detail. This study reveals that a representative from the remaining uncharacterized subgroup is an amino acid racemase with preference toward Leu and Met. Taken together with results of previous studies on enzymes from Pyrococcus horikoshii and Thermococcus kodakarensis, members of the four subgroups now can be presumed to function as a broad-substrate-specificity amino acid racemase (subgroup 1), alanine/serine racemase (subgroup 2), ornithine ω-aminotransferase (subgroup 3), or Leu/Met racemase (subgroup 4).
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11
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Bearne SL. Through the Looking Glass: Chiral Recognition of Substrates and Products at the Active Sites of Racemases and Epimerases. Chemistry 2020; 26:10367-10390. [DOI: 10.1002/chem.201905826] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/09/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Stephen L. Bearne
- Department of Biochemistry & Molecular BiologyDepartment of ChemistryDalhousie University Halifax, Nova Scotia B3H 4R2 Canada
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12
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Maguire OR, Taylor B, Higgins EM, Rees M, Cobb SL, Simpkins NS, Hayes CJ, O'Donoghue AC. Unusually high α-proton acidity of prolyl residues in cyclic peptides. Chem Sci 2020; 11:7722-7729. [PMID: 34094148 PMCID: PMC8159430 DOI: 10.1039/d0sc02508a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The acidity of the α-proton in peptides has an essential role in numerous biochemical reactions and underpins their stereochemical integrity, which is critical to their biological function. We report a detailed kinetic and computational study of the acidity of the α-proton in two cyclic peptide systems: diketopiperazine (DKP) and triketopiperazine (TKP). The kinetic acidity (protofugality) of the α-protons were determined though hydrogen deuterium exchange studies in aqueous solutions. The acidities of the α-proton in prolyl residues were increased by 3–89 fold relative to other amino acid residues (prolyl > glycyl ≫ alanyl > tyrosyl). Experimental and computational evidence for the stereoelectronic origins of this enhanced prolyl reactivity is presented. TKPs were 106-fold more reactive than their DKP analogues towards deprotonation, which we attribute to the advanced development of aromaticity in the earlier transition state for proton transfer in these cases. A Brønsted linear free energy analysis of the reaction data was conducted to provide estimates of α-proton pKas. Kinetic and computational studies reveal that prolyl residues in cyclic peptides are substantially more acidic than other residues due to a stereoelectronic effect.![]()
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Affiliation(s)
| | - Bethany Taylor
- Department of Chemistry
- Durham University
- Durham DH1 3LE
- UK
| | | | - Matthew Rees
- School of Chemistry
- University of Birmingham
- Birmingham
- UK
| | - Steven L. Cobb
- Department of Chemistry
- Durham University
- Durham DH1 3LE
- UK
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13
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Hai Y, Jenner M, Tang Y. Complete Stereoinversion of l-Tryptophan by a Fungal Single-Module Nonribosomal Peptide Synthetase. J Am Chem Soc 2019; 141:16222-16226. [PMID: 31573806 DOI: 10.1021/jacs.9b08898] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Single-module nonribosomal peptide synthetases (NRPSs) and NRPS-like enzymes activate and transform carboxylic acids in both primary and secondary metabolism and are of great interest due to their biocatalytic potentials. The single-module NRPS IvoA is essential for fungal pigment biosynthesis. Here, we show that IvoA catalyzes ATP-dependent unidirectional stereoinversion of l-tryptophan to d-tryptophan with complete conversion. While the stereoinversion is catalyzed by the epimerization (E) domain, the terminal condensation (C) domain stereoselectively hydrolyzes d-tryptophanyl-S-phosphopantetheine thioester and thus represents a noncanonical C domain function. Using IvoA, we demonstrate a biocatalytic stereoinversion/deracemization route to access a variety of substituted d-tryptophan analogs in high enantiomeric excess.
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Affiliation(s)
| | - Matthew Jenner
- Department of Chemistry , University of Warwick , Coventry CV4 7AL , United Kingdom.,Warwick Integrative Synthetic Biology (WISB) Centre , University of Warwick , Coventry CV4 7AL , United Kingdom
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