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Nagaoka S, Sugiyama N, Yatsunami R, Nakamura S. Characterization of 3-isopropylmalate dehydrogenase from extremely halophilic archaeon Haloarcula japonica. Biosci Biotechnol Biochem 2021; 85:1986-1994. [PMID: 34215877 DOI: 10.1093/bbb/zbab122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 06/21/2021] [Indexed: 11/12/2022]
Abstract
3-Isopropylmalate dehydrogenase (IPMDH) catalyzes oxidative decarboxylation of (2R, 3S)-3-isopropylmalate to 2-oxoisocaproate in leucine biosynthesis. In this study, recombinant IPMDH (HjIPMDH) from an extremely halophilic archaeon, Haloarcula japonica TR-1, was characterized. Activity of HjIPMDH increased as KCl concentration increased, and the maximum activity was observed at 3.0 m KCl. Analytical ultracentrifugation revealed that HjIPMDH formed a homotetramer at high KCl concentrations, and it dissociated to a monomer at low KCl concentrations. Additionally, HjIPMDH was thermally stabilized by higher KCl concentrations. This is the first report on haloarchaeal IPMDH.
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Affiliation(s)
- Shintaro Nagaoka
- School of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Noriko Sugiyama
- School of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Rie Yatsunami
- School of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Satoshi Nakamura
- School of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan.,National Institute of Technology (KOSEN), Numazu College, Numazu, Shizuoka, Japan
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2
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Duplication and Functional Divergence of Branched-Chain Amino Acid Biosynthesis Genes in Aspergillus nidulans. mBio 2021; 12:e0076821. [PMID: 34154419 PMCID: PMC8262921 DOI: 10.1128/mbio.00768-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Fungi, bacteria, and plants, but not animals, synthesize the branched-chain amino acids: leucine, isoleucine, and valine. While branched-chain amino acid (BCAA) biosynthesis has been well characterized in the yeast Saccharomyces cerevisiae, it is incompletely understood in filamentous fungi. The three BCAAs share several early biosynthesis steps before divergence into specific pathways. In Aspergillus nidulans, the genes for the first two dedicated steps in leucine biosynthesis have been characterized, but the final two have not. We used sequence searches of the A. nidulans genome to identify two genes encoding β-isopropylmalate dehydrogenase, which catalyzes the penultimate step of leucine biosynthesis, and six genes encoding BCAA aminotransferase, which catalyzes the final step in biosynthesis of all three BCAA. We have used combinations of gene knockouts to determine the relative contribution of each of these genes to BCAA biosynthesis. While both β-isopropylmalate dehydrogenase genes act in leucine biosynthesis, the two most highly expressed BCAA aminotransferases are responsible for BCAA biosynthesis. We have also characterized the expression of leucine biosynthesis genes using reverse transcriptase-quantitative PCR and found regulation in response to leucine availability is mediated through the Zn(II)2Cys6 transcription factor LeuB. IMPORTANCE Branched-chain amino acid (BCAA) biosynthesis is important for pathogenic fungi to successfully cause disease in human and plant hosts. The enzymes for their production are absent from humans and, therefore, provide potential antifungal targets. While BCAA biosynthesis is well characterized in yeasts, it is poorly understood in filamentous fungal pathogens. Developing a thorough understanding of both the genes encoding the metabolic enzymes for BCAA biosynthesis and how their expression is regulated will inform target selection for antifungal drug development.
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Amorim Franco TM, Blanchard JS. Bacterial Branched-Chain Amino Acid Biosynthesis: Structures, Mechanisms, and Drugability. Biochemistry 2017; 56:5849-5865. [PMID: 28977745 DOI: 10.1021/acs.biochem.7b00849] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The eight enzymes responsible for the biosynthesis of the three branched-chain amino acids (l-isoleucine, l-leucine, and l-valine) were identified decades ago using classical genetic approaches based on amino acid auxotrophy. This review will highlight the recent progress in the determination of the three-dimensional structures of these enzymes, their chemical mechanisms, and insights into their suitability as targets for the development of antibacterial agents. Given the enormous rise in bacterial drug resistance to every major class of antibacterial compound, there is a clear and present need for the identification of new antibacterial compounds with nonoverlapping targets to currently used antibacterials that target cell wall, protein, mRNA, and DNA synthesis.
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Affiliation(s)
- Tathyana M Amorim Franco
- Department of Biochemistry, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10805, United States
| | - John S Blanchard
- Department of Biochemistry, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10805, United States
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Tomita T. Structure, function, and regulation of enzymes involved in amino acid metabolism of bacteria and archaea. Biosci Biotechnol Biochem 2017; 81:2050-2061. [PMID: 28840778 DOI: 10.1080/09168451.2017.1365593] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Amino acids are essential components in all organisms because they are building blocks of proteins. They are also produced industrially and used for various purposes. For example, L-glutamate is used as the component of "umami" taste and lysine has been used as livestock feed. Recently, many kinds of amino acids have attracted attention as biological regulators and are used for a healthy life. Thus, to clarify the mechanism of how amino acids are biosynthesized and how they work as biological regulators will lead to further effective utilization of them. Here, I review the leucine-induced-allosteric activation of glutamate dehydrogenase (GDH) from Thermus thermophilus and the relationship with the allosteric regulation of GDH from mammals. Next, I describe structural insights into the efficient production of L-glutamate by GDH from an excellent L-glutamate producer, Corynebacterium glutamicum. Finally, I review the structural biology of lysine biosynthesis of thermophilic bacterium and archaea.
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Affiliation(s)
- Takeo Tomita
- a Department of Biotechnology, Biotechnology Research Center , The University of Tokyo , Tokyo , Japan
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5
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Takahashi K, Tomita T, Kuzuyama T, Nishiyama M. Determinants of dual substrate specificity revealed by the crystal structure of homoisocitrate dehydrogenase from Thermus thermophilus in complex with homoisocitrate·Mg(2+)·NADH. Biochem Biophys Res Commun 2016; 478:1688-93. [PMID: 27601325 DOI: 10.1016/j.bbrc.2016.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 09/01/2016] [Indexed: 11/17/2022]
Abstract
HICDH (Homoisocitrate dehydrogenase) is a member of the β-decarboxylating dehydrogenase family that catalyzes the conversion of homoisocitrate to α-ketoadipate using NAD(+) as a coenzyme, which is the fourth reaction involved in lysine biosynthesis through the α-aminoadipate pathway. Although typical HICDHs from fungi and yeast exhibit strict substrate specificities toward homoisocitrate (HIC), HICDH from a thermophilic bacterium Thermus thermophilus (TtHICDH) catalyzes the reactions using both HIC and isocitrate (IC) as substrates at similar efficiencies. We herein determined the crystal structure of the quaternary complex of TtHICDH with HIC, NADH, and Mg(2+) ion at a resolution of 2.5 Å. The structure revealed that the distal carboxyl group of HIC was recognized by the side chains of Ser72 and Arg85 from one subunit, and Asn173 from another subunit of a dimer unit. Model structures were constructed for TtHICDH in complex with IC and also for HICDH from Saccharomyces cerevisiae (ScHICDH) in complex with HIC. TtHICDH recognized the distal carboxyl group of IC by Arg85 in the model. In ScHICDH, the distal carboxyl group of HIC was recognized by the side chains of Ser98 and Ser108 from one subunit and Asn208 from another subunit of a dimer unit. By contrast, in ScHICDH, which lacks an Arg residue at the position corresponding to Arg85 in TtHICDH, these residues may not interact with the distal carboxyl group of shorter IC. These results provide a molecular basis for the differences in substrate specificities between TtHICDH and ScHICDH.
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Affiliation(s)
- Kento Takahashi
- Biotechnology Research Center, The University of Tokyo, Japan
| | - Takeo Tomita
- Biotechnology Research Center, The University of Tokyo, Japan
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6
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Characterization of two β-decarboxylating dehydrogenases from Sulfolobus acidocaldarius. Extremophiles 2016; 20:843-853. [DOI: 10.1007/s00792-016-0872-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
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7
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Metabolic engineering of Corynebacterium glutamicum for 2-ketoisocaproate production. Appl Microbiol Biotechnol 2013; 98:297-311. [DOI: 10.1007/s00253-013-5310-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 10/26/2022]
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8
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Kirschenbaum DM. Molar absorptivity and 1 1cm values for proteins at selected wavelengths of the ultraviolet and visible region. IV. INTERNATIONAL JOURNAL OF PROTEIN RESEARCH 2009; 3:329-37. [PMID: 5137322 DOI: 10.1111/j.1399-3011.1971.tb01727.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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9
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Abstract
3-isopropylmalate dehydrogenase (IPMDH) from the psychrotrophic bacterium Vibrio sp. I5 has been expressed in Escherichia coli and purified. This cold-adapted enzyme is highly homologous with IPMDHs from other organisms, including mesophilic E. coli and thermophilic Thermus thermophilus bacteria. Its molecular properties are similar to these counterparts. Whereas the E. coli and T. thermophilus enzymes are hardly active at room temperature, the Vibrio IPMDH has reasonable activity below room temperature. The thermal stabilities, conformational flexibilities (hydrogen-deuterium exchange), and kinetic parameters of these enzymes were compared. The temperature dependence of the catalytic parameters of the three enzymes show similar but shifted profiles. The Vibrio IPMDH is a much better enzyme at 25 degrees C than its counterparts. With decreasing temperature i.e. with decreasing conformational flexibility, the specific activity reduces, as well; however, in the case of the Vibrio enzyme, the residual activity is still high enough for normal physiological operation of the organism. The cold-adaptation strategy in this case is achieved by creation of an extremely efficient enzyme, which has reduced but still sufficient activity at low temperature.
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Affiliation(s)
- A Svingor
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, H-1113 Karolina út 29, Budapest, Hungary
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10
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Howell DM, Graupner M, Xu H, White RH. Identification of enzymes homologous to isocitrate dehydrogenase that are involved in coenzyme B and leucine biosynthesis in methanoarchaea. J Bacteriol 2000; 182:5013-6. [PMID: 10940051 PMCID: PMC111387 DOI: 10.1128/jb.182.17.5013-5016.2000] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two putative Methanococcus jannaschii isocitrate dehydrogenase genes, MJ1596 and MJ0720, were cloned and overexpressed in Escherichia coli, and their gene products were tested for the ability to catalyze the NAD- and NADP-dependent oxidative decarboxylation of DL-threo-3-isopropylmalic acid, threo-isocitrate, erythro-isocitrate, and homologs of threo-isocitrate. Neither enzyme was found to use any of the isomers of isocitrate as a substrate. The protein product of the MJ1596 gene, designated AksF, catalyzed the NAD-dependent decarboxylation of intermediates in the biosynthesis of 7-mercaptoheptanoic acid, a moiety of methanoarchaeal coenzyme B (7-mercaptoheptanylthreonine phosphate). These intermediates included (-)-threo-isohomocitrate [(-)-threo-1-hydroxy-1,2, 4-butanetricarboxylic acid], (-)-threo-iso(homo)(2)citrate [(-)-threo-1-hydroxy-1,2,5-pentanetricarboxylic acid], and (-)-threo-iso(homo)(3)citrate [(-)-threo-1-hydroxy-1,2, 6-hexanetricarboxylic acid]. The protein product of MJ0720 was found to be alpha-isopropylmalate dehydrogenase (LeuB) and was found to catalyze the NAD-dependent decarboxylation of one isomer of DL-threo-isopropylmalate to 2-ketoisocaproate; thus, it is involved in the biosynthesis of leucine. The AksF enzyme proved to be thermostable, losing only 10% of its enzymatic activity after heating at 100 degrees C for 10 min, whereas the LeuB enzyme lost 50% of its enzymatic activity after heating at 80 degrees C for 10 min.
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Affiliation(s)
- D M Howell
- Department of Biochemistry (0308), Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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11
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Kawaguchi H, Inagaki K, Matsunami H, Nakayama Y, Tano T, Tanaka H. Purification and characterization of 3-isopropylmalate dehydrogenase from Thiobacillus thiooxidans. J Biosci Bioeng 2000; 90:459-61. [PMID: 16232891 DOI: 10.1016/s1389-1723(01)80020-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2000] [Accepted: 07/10/2000] [Indexed: 11/17/2022]
Abstract
3-Isopropylmalate dehydrogenase was purified to homogeneity from the acidophilic autotroph Thiobacillus thiooxidans. The native enzyme was a dimer of molecular weight 40,000. The apparent K(m) values for 3-isopropylmalate and NAD+ were estimated to be 0.13 mM and 8.7 mM, respectively. The optimum pH for activity was 9.0 and the optimum temperature was 65 degrees C. The properties of the enzyme were similar to those of the Thiobacillus ferrooxidans enzyme, expect for substrate specificity. T. thiooxidans 3-isopropylmalate dehydrogenase could not utilize malate as a substrate.
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Affiliation(s)
- H Kawaguchi
- Department of Bioresources Chemistry, Faculty of Agriculture, Okayama University, Okayama 700-8530, Japan
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12
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KAWAGUCHI HIROSHI, INAGAKI KENJI, MATSUNAMI HIDEYUKI, NAKAYAMA YUMI, TANO TATSUO, TANAKA HIDEHIKO. Purification and Characterization of 3-Isopropylmalate Dehydrogenase from Thiobacillus thiooxidans. J Biosci Bioeng 2000. [DOI: 10.1263/jbb.90.459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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13
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Matsunami H, Kawaguchi H, Inagaki K, Eguchi T, Kakinuma K, Tanaka H. Overproduction and substrate specificity of 3-isopropylmalate dehydrogenase from Thiobacillus ferrooxidans. Biosci Biotechnol Biochem 1998; 62:372-3. [PMID: 9532798 DOI: 10.1271/bbb.62.372] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We constructed an overexpression system in Escherichia coli of the leuB gene coding for 3-isopropylmalate dehydrogenase in Thiobacillus ferrooxidans. E. coli harboring the plasmid we constructed, pKK leuB1, produced 17-fold the enzyme protein of the expression system previously used for purification. The substrate specificity of the enzyme was analyzed with synthetic (2R, 3S)-3-alkylmalates. The 3-isopropylmalate dehydrogenase of Thiobacillus ferrooxidans had broad specificity toward the alkylmalates.
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Affiliation(s)
- H Matsunami
- Department of Bioresources Chemistry, Faculty of Agriculture, Okayama University, Japan
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14
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Sarker MR, Akimoto S, Ugai H, Kuwahara T, Ohnishi Y. Nucleotide sequence of the gene encoding beta-isopropylmalate dehydrogenase (leuB) from Bacteroides fragilis. Microbiol Immunol 1995; 39:525-9. [PMID: 8569539 DOI: 10.1111/j.1348-0421.1995.tb02238.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The complete nucleotide sequence of the gene (leuB) coding for beta-isopropylmalate dehydrogenase of Bacteroides fragilis was determined. An open reading frame of 1,061 nucleotides was detected that could encode a polypeptide of 353 amino acid residues with a calculated molecular mass of 39,179 Da. The deduced amino acid sequence of the beta-isopropylmalate dehydrogenase from B. fragilis showed substantial sequence similarity with the beta-isopropylmalate dehydrogenases from other bacteria.
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Affiliation(s)
- M R Sarker
- Department of Bacteriology, School of Medicine, University of Tokushima, Japan
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15
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Sarker MR, Akimoto S, Ono T, Kinouchi T, Ohnishi Y. Molecular cloning of the leuB gene from Bacteroides fragilis by functional complementation in Escherichia coli. Microbiol Immunol 1995; 39:19-25. [PMID: 7783674 DOI: 10.1111/j.1348-0421.1995.tb02163.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Clones containing the Bacteroides fragilis leuB-complementing gene were isolated by screening of a B. fragilis genomic library constructed in Escherichia coli. One recombinant clone, designated pOT865, with the smallest DNA insert (4.5 kb) could complement three independent leuB mutations in E. coli and the leuB-complementing determinant in pOT865 was localized to a region of 1.5-kb DNA. The results of Southern blot analysis suggested that a single copy of the cloned gene was present in the B. fragilis genome. The cloned fragment appeared to contain a sequence that could function as promoter in E. coli and direct the synthesis of a 42-kDa protein. These results suggest that the cloned segment contains the structural gene for beta-isopropylmalate dehydrogenase (leuB).
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Affiliation(s)
- M R Sarker
- Department of Bacteriology, School of Medicine, University of Tokushima, Japan
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16
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Bode R. Valine inhibition of beta-isopropylmalate dehydrogenase takes part in the regulation of leucine biosynthesis in Candida maltosa. Antonie Van Leeuwenhoek 1991; 60:125-30. [PMID: 1804028 DOI: 10.1007/bf00572702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The beta-isopropylmalate (IPM) dehydrogenase (EC 1.1.1.85) of Candida maltosa, the third pathway-specific enzyme of leucine biosynthesis, was purified, some properties of the enzyme were studied and a novel regulatory pattern was found. The Km values of the enzyme were estimated to be 0.42 mM for beta-IPM and 0.34 mM for NAD+. It is demonstrated that the enzyme can be regulated by L-valine. The inhibition was competitive with respect to beta-IPM (Ki = 1.84 mM) and non-competitive with respect to NAD+ (Ki = 5.67 mM). Exogenous addition of L-valine to C. maltosa cells increased the intracellular pool of some intermediates of leucine biosynthesis (alpha-ketoisovalerate, alpha-IPM, beta-IPM), but has hardly influence on the leucine pool.
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Affiliation(s)
- R Bode
- Institut für Biochemie, Ernst-Moritz-Arndt-Universität Greifswald, Germany
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17
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Bode R, Birnbaum D. Some properties of the leucine-biosynthesizing enzymes fromCandida maltosa. J Basic Microbiol 1991. [DOI: 10.1002/jobm.3620310104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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18
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Searles LL, Calvo JM. Permeabilized cell and radiochemical assays for beta-isopropylmalate dehydrogenase. Methods Enzymol 1988; 166:225-9. [PMID: 3071705 DOI: 10.1016/s0076-6879(88)66029-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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19
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Characterization of the 3' end of the leucine operon of Salmonella typhimurium. MOLECULAR & GENERAL GENETICS : MGG 1985; 199:486-94. [PMID: 2993799 DOI: 10.1007/bf00330763] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The nucleotide sequence of the leuD gene of Salmonella typhimurium and of the downstream flanking region are presented. S1 mapping experiments identified 3' endpoints of leu mRNA 140 and 285 nucleotides downstream of the UAA stop codon of leuD mRNA. Experiments employing pulse-labeled RNA suggest that these endpoints result from transcription termination rather than RNA processing. Our results indicate that the organization of the 3' non-translated region of the leu operon from S. typhimurium resembles that of the trp operon of Escherichia coli. Further, our results suggest that the leu operon of S. typhimurium does not contain structural genes other than those identified by genetic experiments, i.e. leu, A,B,C and D.
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20
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Carter PW, Weiss DL, Weith HL, Calvo JM. Mutations that convert the four leucine codons of the Salmonella typhimurium leu leader to four threonine codons. J Bacteriol 1985; 162:943-9. [PMID: 3922957 PMCID: PMC215867 DOI: 10.1128/jb.162.3.943-949.1985] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In Salmonella typhimurium, expression of the leucine operon is regulated by a transcription attenuation mechanism. According to a current model of attenuation, elevated expression of this operon requires that a ribosome stall at one of four adjacent codons for leucine on a leader RNA. We used oligonucleotide-directed mutagenesis to convert the four leucine codons of the S. typhimurium leu leader to four threonine codons. Analysis of the resulting mutant operon showed that almost all regulation by leucine had been abolished. The mutant operon was, instead, partially derepressed by a limitation for charged threonine tRNA. These results provide direct evidence for the function for the four leucine codons postulated by the attenuator model. An unexpected observation made during these studies was that the wild-type leu operon was partially derepressed by starvation for threonine.
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Searles LL, Wessler SR, Calvo JM. Transcription attenuation is the major mechanism by which the leu operon of Salmonella typhimurium is controlled. J Mol Biol 1983; 163:377-94. [PMID: 6187929 DOI: 10.1016/0022-2836(83)90064-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Three mutations, each causing constitutive expression of the Salmonella typhimurium leu operon, were cloned into phage vector lambda gt4 on EcoRI DNA fragments carrying all of that operon except for part of the promoter-distal last gene. Sequence analysis of DNA from these phage demonstrated that each contains a single base change in the leu attenuator. Transcription of mutant DNA in vitro resulted in transcription beyond the usual site of termination. The level of beta-IPM dehydrogenase, the leuB enzyme, was elevated 40-fold in a strain carrying one of these mutations, and starvation of this strain for leucine had little effect on the amount of activity expressed. Using a strain with a wild-type promoter-leader region of the leu operon, the rates of synthesis and degradation of leu leader RNA and readthrough RNA (leu mRNA) were measured by DNA-RNA hybridizations with specific DNA probes. The rate of synthesis of the leu leader was about the same in cells grown with excess or with limiting leucine. On the other hand, the rate of synthesis of leu mRNA was 12-fold higher for cells grown in limiting leucine as opposed to excess leucine. The rate of degradation of these RNA species was the same under both conditions of growth. Thus, the variation in expression of the leu operon observed for cells grown in minimal medium is, for the most part, not caused by control over the frequency of initiation or by the differential stability of these RNA species. Rather, the variation is a direct result of the frequency of transcription termination at an attenuator site. These results taken together suggest that transcription attenuation is the major mechanism by which leucine regulates expression of the leu operon of S. typhimurium for cells growing in a minimal medium.
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22
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Kung H, Weissbach H. DNA-directed in vitro synthesis of Escherichia coli beta-isopropylmalate dehydrogenase. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)38041-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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23
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Kirschenbaum DM. A compilation of amino acid analyses of proteins, polypeptides, and peptides. XII. Residues per molecule--9. Anal Biochem 1977; 83:484-520. [PMID: 341744 DOI: 10.1016/0003-2697(77)90056-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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24
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Jackson J, Williams LS, Umbarger HE. Regulation of synthesis of the branched-chain amino acids and cognate aminoacyl-transfer ribonucleic acid synthetases of Escherichia coli: a common regulatory element. J Bacteriol 1974; 120:1380-6. [PMID: 4612020 PMCID: PMC245925 DOI: 10.1128/jb.120.3.1380-1386.1974] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Regulation of isoleucine, valine, and leucine biosynthesis and isoleucyl-, valyl-, and leucyl-transfer ribonucleic acid (tRNA) synthetase formation was examined in two mutant strains of Escherichia coli. One mutant was selected for growth resistance to the isoleucine analogue, ketomycin, and the other was selected for growth resistance to both trifluoroleucine and valine. Control of the synthesis of the branched-chain amino acids by repression was altered in both of these mutants. They also exhibited altered control of formation of isoleucyl-tRNA synthetase (EC 6.1.15, isoleucine:sRNA ligase, AMP), valyl-tRNA synthetase (EC 6.1.1.9, valine:sRNA ligase, AMP), and leucyl-tRNA synthetase (EC 6.1.1.4, leucine:sRNA ligase, AMP). These results suggest the existence of a common element for the control of these two classes of enzymes in Escherichia coli.
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25
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Graf LH, Burns RO. The supX-leu-500 mutations and expression of the leucine operon. MOLECULAR & GENERAL GENETICS : MGG 1973; 126:291-301. [PMID: 4593993 DOI: 10.1007/bf00269439] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Abstract
The mutations in a series of leucine auxotrophs isolated after treatment with nitrosoguanidine, ultraviolet light, and ICR-191 have been mapped between ilvC and pheA on the Bacillus subtilis chromosome. A fine structure map of the region was constructed by transformation. Analysis of several strains by assaying levels of their leucine bioysnthetic enzymes has shown that the region encodes three enzymes. The order of the genes with respect to the biosynthetic steps catalyzed by the gene products is 1-3-2.
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Bartholomew JC, Calvo JM. Alpha-isopropylmalate synthase from Salmonella typhimurium--amino acid composition, NH 2 -terminal analysis, and fingerprint analysis. BIOCHIMICA ET BIOPHYSICA ACTA 1971; 250:577-87. [PMID: 4943723 DOI: 10.1016/0005-2744(71)90258-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Rabin R, Urbano C, Ajl SJ. Isoenzymes of beta-isopropylmalate dehydrogenase from Pseudomonas aeruginosa. Arch Biochem Biophys 1969; 134:259-61. [PMID: 4310224 DOI: 10.1016/0003-9861(69)90277-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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