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Gupta P, Jain M, Sarangthem J, Gadre R. Inhibition of 5-aminolevulinic acid dehydratase by mercury in excised greening maize leaf segments. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013. [PMID: 23191957 DOI: 10.1016/j.plaphy.2012.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Mercury (Hg), a potent metallic toxicant, is known for having inhibitory effect on chlorophyll biosynthesis. In vivo supply of HgCl(2) inhibited 5-aminolevulinic acid dehydratase (ALAD, EC 4.2.1.24) activity in excised greening maize (Zea mays) leaf segments. The inhibition caused by Hg was alleviated by addition of KNO(3). Amongst the nutrients and metabolites tested, NH(4)Cl and sucrose increased the inhibitory effect of Hg on enzyme activity, while glutamine and glutathione decreased it. The inhibitors, levulinic acid and 5,5' dithio bis 2-nitrobenzoic acid, also reduced the % inhibition of enzyme activity caused by Hg supply. In vitro inclusion of Hg during assay of the enzyme preparations obtained from the tissue treated without Hg (-Hg enzyme) and with Hg (+Hg enzyme) caused the inhibition of -Hg enzyme but activation of +Hg enzyme. Almost similar trend was observed for the in vitro inclusion of Hg in the presence of levulinic acid. It is suggested that two forms of enzyme exist in Hg-treated tissue, i.e. the usual Mg dependent form and an unusual Hg modified form. Kinetic studies for the two enzymes, -Hg enzyme and +Hg enzyme, involving the effect of varying concentrations of δ-aminolevulinic acid yielded distinct apparent K(m) and apparent V(max) values being 532 μM and 118 units g(-1) fr. wt., respectively, for -Hg enzyme and 347 μM and 52 units g(-1) fr. wt., respectively, for +Hg enzyme indicating that +Hg enzyme has higher affinity for δ-aminolevulinic acid but lower activity as compared to the -Hg enzyme.
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Affiliation(s)
- Priyanka Gupta
- School of Biochemistry, Devi Ahilya University, Takshashila Campus, Khandwa Road, Indore 452 017, Madhya Pradesh, India
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Abstract
The ease of formation of cyclic structures shows some regularity which can be described by a set of 'rules' for ring closure. The restrictions on the endocyclic transfer of groups due to SN2 displacements having linear transition states are exemplified by studied on a biogenetic type synthesis of penicillin and, more generally, on the endocyclic attack of a nucleophile attached by a linking chain to an enone or polarized double bond. The formation of five-memebered rings is considered. In base, enones such as 4-hydroxy- and 4-amino-2-methylenebutanoates close exocyclically to give the corresponding five-membered lactones and lactams, respectively. Hydroxymethyl vinyl ketones, however, do not cyclize in base. In strong acid, hydroxy-enones close endocyclically to five-membered ring, as in the formation of cyclic ethylene ketals from acetone and ethanediol. The endocyclic closure of nucleophilic centres to polarized double bonds to give five-membered rings is impeded by restrictions of geometry; these restrictions can be overcome in acid through the generation of oxonium or protonated forms.
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Kutlu M, Sümer S. Some biochemical properties of delta-aminolevulinic acid dehydratase in Gammarus pulex. Food Chem Toxicol 2007; 46:115-8. [PMID: 17904721 DOI: 10.1016/j.fct.2007.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 07/01/2007] [Accepted: 07/09/2007] [Indexed: 10/23/2022]
Abstract
The determination of delta-aminolevulinic acid dehydratase (ALAD; porphobilinogen synthetase, EC 4.2.1.24) activity in aquatic organisms might be a useful marker for the identification of lead exposure. ALADs from the variety of different sources have been grouped into two classes based on some biochemical properties such as molecular weight, pH optimum, metal requirement and susceptibility to EDTA. The first group includes the enzymes from mammals and birds, while the second group ALADs are derived primarily from bacteria and yeasts. In this study, we have characterized Gammarus ALAD in some biochemical aspects. Gammarus pulex were collected from the Porsuk River at Eskişehir (Turkey). The effect of pH, incubation temperature of reaction mixture, incubation period, metal ions and EDTA on enzyme activity were investigated. Comparisons between groups were performed by analysis of a paired t-test. Gammarus ALAD was found biochemically distinct from the mammalian enzyme. It seems to be considered in Class II rather than Class I.
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Affiliation(s)
- M Kutlu
- Department of Biology, Faculty of Science, Anadolu University, 26470 Eskişehir, Turkey.
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Spencer P, Jordan PM. 5-Aminolaevulinic acid dehydratase: characterization of the alpha and beta metal-binding sites of the Escherichia coli enzyme. CIBA FOUNDATION SYMPOSIUM 2007; 180:50-64; discussion 64-9. [PMID: 7842862 DOI: 10.1002/9780470514535.ch4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The alpha and beta metal-binding sites of 5-aminolaevulinic acid dehydratase (ALAD) (porphobilinogen synthase, EC 4.2.1.24) from Escherichia coli were investigated to determine the function of each metal ion and the role of the reactive cysteines in metal binding. Occupancy of the alpha site by Zn2+ restored virtually all catalytic activity to the inactive metal-depleted ALAD (apoALAD). Occupancy of the alpha site by Co2+ also yielded an active enzyme and resulted in a charge-transfer band indicative of a single cysteine amongst the metal ligands. Subsequent labelling of this cysteine residue with 14C-labelled N-ethylmaleimide, followed by peptide analysis, indicated the involvement of Cys-130. The metal ion at the alpha site is thought to be essential for binding of the second molecule of substrate at the A substrate-binding site that forms the acetic acid side of the product, porphobilinogen. Binding of Zn2+ to the beta site restored little activity if the alpha site was unfilled. Metal ion binding to the beta site could be monitored by following the change in protein fluorescence with Zn2+ titration of apoALAD at pH 6. A conformational change upon beta site occupancy may explain why binding of Mg2+ at the alpha site can occur only if Zn2+ is bound at the beta site. The binding of Co2+ at the beta site produced an inactive enzyme that exhibited a charge-transfer band indicative of at least three cysteine ligands.
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Affiliation(s)
- P Spencer
- School of Biological Sciences, Queen Mary and Westfield College, University of London, UK
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Vallee BL, Galdes A. The metallobiochemistry of zinc enzymes. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 56:283-430. [PMID: 6364704 DOI: 10.1002/9780470123027.ch5] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Mehta A, Flora SJ. Possible role of metal redistribution, hepatotoxicity and oxidative stress in chelating agents induced hepatic and renal metallothionein in rats. Food Chem Toxicol 2001; 39:1029-38. [PMID: 11524141 DOI: 10.1016/s0278-6915(01)00046-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A study was planned to investigate possible role of oxidative stress, hepato- and nephrotoxicity and essential metal redistribution following administration of amino and thiol chelating agents on hepatic and renal metallothionein (MT) and the levels of some metalloenzymes in male rats. Animals were administered 50 mg/kg, intraperitoneally, twice daily for 15 consecutive days; a dose of three amino and four thiol chelators and were sacrificed 24 h after the last dose. The results indicate no evidence of oxidative stress in hepatic and renal tissues of rats administered thiol and amino chelators, except for some marginal changes in the animals treated with calcium disodium ethylenediaminetetraacetic acid (EDTA) and D-penicillamine (DPA). Redistribution of essential metal (particularly zinc), hepato- and nephrotoxicity seems to play a significant role in influencing the MT induction by amino chelators. Redistribution of essential metals may also be playing a significant role in a number of metalloenzymes, especially by amino chelators compared to thiol chelators. It can thus be concluded that toxic effects of chelating agents, including metal redistribution and hepatotoxicity, might be playing a crucial role in the metallothionein induction.
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Affiliation(s)
- A Mehta
- Division of Pharmacology and Toxicology, Defence Research and Development Establishment, Jhansi Road, Gwalior-474 002, India
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Jarret C, Stauffer F, Henz ME, Marty M, Lüönd RM, Bobálová J, Schürmann P, Neier R. Inhibition of Escherichia coli porphobilinogen synthase using analogs of postulated intermediates. CHEMISTRY & BIOLOGY 2000; 7:185-96. [PMID: 10712932 DOI: 10.1016/s1074-5521(00)00089-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Porphobilinogen synthase is the second enzyme involved in the biosynthesis of natural tetrapyrrolic compounds, and condenses two molecules of 5-aminolevulinic acid (ALA) through a nonsymmetrical pathway to form porphobilinogen. Each substrate is recognized individually at two different active site positions to be regioselectively introduced into the product. According to pulse-labeling experiments, the substrate forming the propionic acid sidechain of porphobilinogen is recognized first. Two different mechanisms for the first bond-forming step between the two substrates have been proposed. The first involves carbon-carbon bond formation (an aldol-type reaction) and the second carbon-nitrogen bond formation, leading to an iminium ion. RESULTS With the help of kinetic studies, we determined the Michaelis constants for each substrate recognition site. These results explain the Michaelis-Menten behavior of substrate analog inhibitors - they act as competitive inhibitors. Under standard conditions, however, another set of inhibitors demonstrates uncompetitive, mixed, pure irreversible, slow-binding or even quasi-irreversible inhibition behavior. CONCLUSIONS Analysis of the different classes of inhibition behavior allowed us to make a correlation between the type of inhibition and a specific site of interaction. Analyzing the inhibition behavior of analogs of postulated intermediates strongly suggests that carbon-nitrogen bond formation occurs first.
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Affiliation(s)
- C Jarret
- Institute of Chemistry, University of Neuchâtel, Neuchâtel, CH-2000, Switzerland
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Chemical synthesis of porphobilinogen and studies of its biosynthesis. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1521-4478(06)80004-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Jaffe EK. Predicting the Zn(II) Ligands in Metalloproteins: Case Study, Porphobilinogen Synthase. COMMENT INORG CHEM 1993. [DOI: 10.1080/02603599308035837] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Enhanced intramolecular interligand interaction in tetrahedral Zn(II) and Cd(II) mixed-ligand complexes. J Inorg Biochem 1992. [DOI: 10.1016/0162-0134(92)80032-q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Boese Q, Spano A, Li J, Timko M. Aminolevulinic acid dehydratase in pea (Pisum sativum L.). Identification of an unusual metal-binding domain in the plant enzyme. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)47339-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Jordan PM. Chapter 1 The biosynthesis of 5-aminolaevulinic acid and its transformation into uroporphyrinogen III. BIOSYNTHESIS OF TETRAPYRROLES 1991. [DOI: 10.1016/s0167-7306(08)60108-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Rodrigues AL, Bellinaso ML, Dick T. Effect of some metal ions on blood and liver delta-aminolevulinate dehydratase of Pimelodus maculatus (Pisces, Pimelodidae). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. B, COMPARATIVE BIOCHEMISTRY 1989; 94:65-9. [PMID: 2598636 DOI: 10.1016/0305-0491(89)90012-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. delta-ALA-D from Pimelodus maculatus was inhibited in vitro by Cd2+ greater than Pb2+ greater than Hg2+ greater than Cu2+ greater than Zn2+ in blood and by Pb2+ greater than Cd2+ greater than Hg2+ greater than Cu2+ = Zn2+ in the liver. 2. Kinetic analysis of the inhibition by the metal ions showed that Cd2+ and Hg2+ act as non-competitive inhibitors on both sources. 3. Pb2+ showed a mixed type of inhibition in blood and a non-competitive type in the liver. 4. Zn2+ acted as a competitive or mixed inhibitor, on both sources, depending on concentration.
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Affiliation(s)
- A L Rodrigues
- Departamento de Bioquímica e Centro de Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil
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Beyersmann D, Cox M. Affinity labelling of 5-aminolevulinic acid dehydratase with 2-bromo-3-(5-imidazolyl)propionic acid. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 788:162-6. [PMID: 6430344 DOI: 10.1016/0167-4838(84)90258-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
2-Bromo-3-(5-imidazolyl)propionic acid, a zinc-directed thiol reagent, inactivates the enzyme 5-aminolevulinic acid dehydratase from bovine liver (5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing, EC 4.2.1.24). The substrate, 5-aminolevulinic acid, completely protects against inactivation. The reagent inhibits the zinc-containing enzyme to a greater extent than the zinc-deprived enzyme; and it competes with the zinc chelator 1,10-phenanthroline. The reagent alkylates essential sulfhydryl groups of the enzyme, since the extent of the inactivation depends on the reduction of the enzyme protein by thiol compounds. It is concluded that the zinc site, the substrate site and the essential sulfhydryl groups are in close proximity in the active site.
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Seehra JS, Gore MG, Chaudhry AG, Jordan PM. 5-Aminolevulinic acid dehydratase. The role of sulphydryl groups in 5-aminolevulinic acid dehydratase from bovine liver. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 114:263-9. [PMID: 7215355 DOI: 10.1111/j.1432-1033.1981.tb05145.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The thiophilic reagent 5,5'-dithiobis(2-nitrobenzoic acid) Nbs2) reacts with four sulphydryl groups in native 5-aminolevulinic acid dehydratase from bovine liver (groups I, II, III and IV). All four of these groups exhibit various degrees of half-site reactivity. Groups I and II are highly reactive and their rates of reaction with Nbs2 have been investigated using stopped-flow analysis. The reaction of these groups with Nbs2 results in the formation of an intramolecular disulphide bond which may be reduced with dithioerythritol to regenerate the free sulphydryl groups. Groups I and II appear to be at, or near, the catalytic site whereas group III is involved in the maintenance of conformation in the native enzyme.
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Seehra JS, Jordan PM. 5-Aminolevulinic acid dehydratase: alkylation of an essential thiol in the bovine-liver enzyme by active-site-directed reagents. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 113:435-46. [PMID: 7215335 DOI: 10.1111/j.1432-1033.1981.tb05083.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
1. 5-Aminolevulinic acid dehydratase from bovine liver has been shown to be inactivated by 5-halolevulinic acids and 3-halolevulinic acids. 2. The substrate, 5-aminolevulinic acid, protects the enzyme from modification by 5-halolevulinic acids. 3. Using tritiated chlorolevulinic acids, it was shown that four of the subunits in the octameric enzyme are preferentially modified. 4. The susceptible enzyme group modified is an --SH group of a reactive cysteine at or near the active site. 5. Oxidized enzyme is not affected by either 5-chlorolevulinic acid or 3-chlorolevulinic acid. 6. Evidence is presented which suggests that 5-chlorolevulinic acid is acting as an active-site-directed reagent.
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Abstract
Synthetic metal complexes can closely approach the properties of metal ions in proteins and yield useful information concerning biological structure and function.
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Barnard G, Itoh R, Hohberger L, Shemin D. Mechanism of porphobilinogen synthase. Possible role of essential thiol groups. J Biol Chem 1977. [DOI: 10.1016/s0021-9258(17)38333-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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