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Eaton SS, Woodcock LB, Eaton GR. Continuous wave electron paramagnetic resonance of nitroxide biradicals in fluid solution. CONCEPTS IN MAGNETIC RESONANCE. PART A, BRIDGING EDUCATION AND RESEARCH 2018; 47A:e21426. [PMID: 31548835 PMCID: PMC6756774 DOI: 10.1002/cmr.a.21426] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Nitroxide biradicals have been prepared with electron-electron spin-spin exchange interaction, J, ranging from weak to very strong. EPR spectra of these biradicals in fluid solution depend on the ratio of J to the nitrogen hyperfine coupling, AN, and the rates of interconversion between conformations with different values of J. For relatively rigid biradicals EPR spectra can be simulated as the superposition of AB splitting patterns arising from different combinations of nitrogen nuclear spin states. For more flexible biradicals spectra can be simulated with a Liouville representation of the dynamics that interconvert conformations with different values of J on the EPR timescale. Analysis of spectra, factors that impact J, and examples of applications to chemical and biophysical problems are discussed.
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Affiliation(s)
- Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver CO 80210 USA
| | - Lukas B Woodcock
- Department of Chemistry and Biochemistry, University of Denver, Denver CO 80210 USA
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver CO 80210 USA
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2
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Eaton SS, Woodcock LB, Eaton GR. Continuous wave electron paramagnetic resonance of nitroxide biradicals in fluid solution. CONCEPTS IN MAGNETIC RESONANCE. PART A, BRIDGING EDUCATION AND RESEARCH 2018; 47A:e21426. [PMID: 31548835 DOI: 10.1002/cmr.a.21246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Nitroxide biradicals have been prepared with electron-electron spin-spin exchange interaction, J, ranging from weak to very strong. EPR spectra of these biradicals in fluid solution depend on the ratio of J to the nitrogen hyperfine coupling, AN, and the rates of interconversion between conformations with different values of J. For relatively rigid biradicals EPR spectra can be simulated as the superposition of AB splitting patterns arising from different combinations of nitrogen nuclear spin states. For more flexible biradicals spectra can be simulated with a Liouville representation of the dynamics that interconvert conformations with different values of J on the EPR timescale. Analysis of spectra, factors that impact J, and examples of applications to chemical and biophysical problems are discussed.
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Affiliation(s)
- Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver CO 80210 USA
| | - Lukas B Woodcock
- Department of Chemistry and Biochemistry, University of Denver, Denver CO 80210 USA
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver CO 80210 USA
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Sampaio TB, da Rocha JT, Quines CB, Stein ALA, Zeni G, Nogueira CW. Sulfhydryl-Based Inhibition of δ-ALA-D and Na+
, K+
-ATPase Activities Depends on the Organoselenium Group Bonded to the Isoquinoline. J Cell Biochem 2017; 118:1144-1150. [DOI: 10.1002/jcb.25740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 09/13/2016] [Indexed: 01/28/2023]
Affiliation(s)
- Tuane Bazanella Sampaio
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica e Toxicológica de Organocalcogênios; Departamento de Bioquímica e Biologia Molecular; Centro de Ciências Naturais e Exatas; Universidade Federal de Santa Maria; Santa Maria CEP 97105-900 RS Brazil
| | | | - Caroline Brandão Quines
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica e Toxicológica de Organocalcogênios; Departamento de Bioquímica e Biologia Molecular; Centro de Ciências Naturais e Exatas; Universidade Federal de Santa Maria; Santa Maria CEP 97105-900 RS Brazil
| | - André Luiz Agnes Stein
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica e Toxicológica de Organocalcogênios; Departamento de Bioquímica e Biologia Molecular; Centro de Ciências Naturais e Exatas; Universidade Federal de Santa Maria; Santa Maria CEP 97105-900 RS Brazil
| | - Gilson Zeni
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica e Toxicológica de Organocalcogênios; Departamento de Bioquímica e Biologia Molecular; Centro de Ciências Naturais e Exatas; Universidade Federal de Santa Maria; Santa Maria CEP 97105-900 RS Brazil
| | - Cristina Wayne Nogueira
- Laboratório de Síntese, Reatividade e Avaliação Farmacológica e Toxicológica de Organocalcogênios; Departamento de Bioquímica e Biologia Molecular; Centro de Ciências Naturais e Exatas; Universidade Federal de Santa Maria; Santa Maria CEP 97105-900 RS Brazil
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4
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Elajaili H, Biller JR, Rosen GM, Kao JPY, Tseytlin M, Buchanan LA, Rinard GA, Quine RW, McPeak J, Shi Y, Eaton SS, Eaton GR. Imaging disulfide dinitroxides at 250 MHz to monitor thiol redox status. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 260:77-82. [PMID: 26415686 PMCID: PMC4731354 DOI: 10.1016/j.jmr.2015.08.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 08/15/2015] [Accepted: 08/25/2015] [Indexed: 05/12/2023]
Abstract
Measurement of thiol-disulfide redox status is crucial for characterization of tumor physiology. The electron paramagnetic resonance (EPR) spectra of disulfide-linked dinitroxides are readily distinguished from those of the corresponding monoradicals that are formed by cleavage of the disulfide linkage by free thiols. EPR spectra can thus be used to monitor the rate of cleavage and the thiol redox status. EPR spectra of (1)H,(14)N- and (2)H,(15)N-disulfide dinitroxides and the corresponding monoradicals resulting from cleavage by glutathione have been characterized at 250 MHz, 1.04 GHz, and 9 GHz and imaged by rapid-scan EPR at 250 MHz.
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Affiliation(s)
- Hanan Elajaili
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - Joshua R Biller
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - Gerald M Rosen
- Department of Pharmaceutical Sciences and Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, United States
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, and Department of Physiology, University of Maryland, Baltimore, MD 21201, United States
| | - Mark Tseytlin
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - Laura A Buchanan
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - George A Rinard
- School of Engineering and Computer Science, University of Denver, Denver, CO 80208, United States
| | - Richard W Quine
- School of Engineering and Computer Science, University of Denver, Denver, CO 80208, United States
| | - Joseph McPeak
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - Yilin Shi
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - Sandra S Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
| | - Gareth R Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States.
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Liver δ-aminolevulinate dehydratase activity is inhibited by neonicotinoids and restored by antioxidant agents. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2014; 11:11676-90. [PMID: 25402564 PMCID: PMC4245637 DOI: 10.3390/ijerph111111676] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 11/05/2014] [Accepted: 11/06/2014] [Indexed: 11/17/2022]
Abstract
Neonicotinoids represent the most used class of insecticides worldwide, and their precursor, imidacloprid, is the most widely marketed. The aim of this study was to evaluate the effect of imidacloprid on the activity of hepatic δ-aminolevulinate dehydratase (δ-ALA-D), protective effect of potential antioxidants against this potential effect and presence of chemical elements in the constitution of this pesticide. We observed that δ-ALA-D activity was significantly inhibited by imidacloprid at all concentrations tested in a dose-dependent manner. The IC50 value was obtained and used to evaluate the restoration of the enzymatic activity. δ-ALA-D inhibition was completely restored by addition of dithiotreitol (DTT) and partly by ZnCl2, demonstrating that the inhibition occurs by oxidation of thiol groups and by displacement of the Zn (II), which can be explained by the presence of chemical elements found in the constitution of pesticides. Reduced glutathione (GSH) had the best antioxidant effect against to δ-ALA-D inhibition caused by imidacloprid, followed by curcumin and resveratrol. It is well known that inhibition of the enzyme δ-ALA-D may result in accumulation of its neurotoxic substrate (δ-ALA), in this line, our results suggest that further studies are needed to investigate the possible neurotoxicity induced by neonicotinoids and the involvement of antioxidants in cases of poisoning by neonicotinoids.
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Rocha JBT, Saraiva RA, Garcia SC, Gravina FS, Nogueira CW. Aminolevulinate dehydratase (δ-ALA-D) as marker protein of intoxication with metals and other pro-oxidant situations. Toxicol Res (Camb) 2012. [DOI: 10.1039/c2tx20014g] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Inhibition of hepatic δ-aminolevulinate dehydratase activity induced by mercuric chloride is potentiated by N-acetylcysteine in vitro. Food Chem Toxicol 2010; 49:305-8. [PMID: 21056077 DOI: 10.1016/j.fct.2010.10.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 10/27/2010] [Accepted: 10/29/2010] [Indexed: 11/21/2022]
Abstract
Mercuric chloride (HgCl)(2) is a toxic metal that causes oxidative damage in several tissues. N-acetylcysteine (NAC) is a sulfhydryl compound with antioxidant activity. In the present study, we investigated the in vitro effects of the association between HgCl(2) and NAC in tissues of mice. For this purpose, we evaluated the in vitro effect of HgCl(2)+NAC association on δ-aminolevulinate dehydratase (δ-ALA-D) activity and on thiobarbituric acid reactive substances (TBARS) levels in liver and kidney of mice. The results demonstrate that HgCl(2) inhibited δ-ALA-D activity in both tissues. Hepatic δ-ALA-D activity inhibited by HgCl(2) was potentiated by the highest concentration of NAC. The inhibition of hepatic δ-ALA-D activity seems to be related to sulfhydryl groups oxidation of the enzyme. We observed also that HgCl(2) increased TBARS levels in kidney and liver. Hepatic TBARS levels were reduced by NAC, at higher concentration. In contrast, NAC, at higher concentration, increased renal TBARS levels. In conclusion, the inhibition of hepatic δ-aminolevulinate dehydratase activity induced by HgCl(2) is potentiated by NAC in vitro, and this effect is not related to hepatic lipid peroxidation.
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Rosa R, Roesler R, Braga A, Saffi J, Henriques J. Pharmacology and toxicology of diphenyl diselenide in several biological models. Braz J Med Biol Res 2007; 40:1287-304. [DOI: 10.1590/s0100-879x2006005000171] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- R.M. Rosa
- Universidade Federal do Rio Grande do Sul
| | - R. Roesler
- Universidade Federal do Rio Grande do Sul, Brasil
| | - A.L. Braga
- Universidade Federal de Santa Maria, Brasil
| | - J. Saffi
- Universidade Federal do Rio Grande do Sul; Universidade Luterana do Brasil, Brasil
| | - J.A.P. Henriques
- Universidade Federal do Rio Grande do Sul; Universidade Luterana do Brasil, Brasil
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9
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Nogueira CW, Zeni G, Rocha JBT. Organoselenium and Organotellurium Compounds: Toxicology and Pharmacology. Chem Rev 2004; 104:6255-85. [PMID: 15584701 DOI: 10.1021/cr0406559] [Citation(s) in RCA: 1429] [Impact Index Per Article: 71.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Cristina W Nogueira
- Laboratório de Síntese, Reatividade e Avaliacão Farmacológica e Toxicológica de Organocalcogênios, CCNE, UFSM, Santa Maria, CEP 97105-900 Rio Grande do Sul, Brazil
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Farina M, Brandão R, Lara FS, Soares FAA, Souza DO, Rocha JBT. Mechanisms of the inhibitory effects of selenium and mercury on the activity of delta-aminolevulinate dehydratase from mouse liver, kidney and brain. Toxicol Lett 2003; 139:55-66. [PMID: 12595158 DOI: 10.1016/s0378-4274(02)00454-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mercury is known to interact with selenite and when the two are co-administered, one reduces the toxicity of the other. The main goal of this study was to investigate the simultaneous in vitro effects of sodium selenite (Se(4+)) and mercuric chloride (Hg(2+)) on the activity of hepatic, renal and cerebral delta-aminolevulinate dehydratase (delta-ALA-D) of adult male mice (Swiss albino). Hg(2+) inhibited delta-ALA-D from tissue supernatants and the IC(50) values for hepatic, renal and cerebral enzyme inhibition were 38+/-4.2, 67.5+/-4.3 and 46.2+/-3.7 microM, respectively. Se(4+) displayed a higher inhibitory action toward delta-ALA-D activity than Hg(2+). Simultaneous addition of Se(4+) and Hg(2+) to the delta-ALA-D assay increased the inhibition of the enzyme. Se(4+) and Hg(2+) oxidized total -SH groups from hepatic, renal and cerebral supernatants, although the effect of Se(4+) decreased in the presence of increasing concentrations of Hg(2+). The oxidation of -SH groups from a dithiol (DTT), a monothiol glutathione (GSH) and a protein (albumin) increased in the presence of Hg(2+). Only DTT was oxidized by Se(4+) and the oxidation decreased in the presence of Hg(2+), suggesting the formation of a chemical complex. This complex did not inhibit delta-ALA-D. These results suggest a similar inhibitory mechanism of Se(4+) and Hg(2+) on delta-ALA-D in which oxidation of sulfhydryl groups located at the active site of the enzyme is an essential step. Furthermore, decreasing oxidative effects of selenite on sulfhydryl groups from DTT in the presence of mercury are believed to occur as the result of the formation of an inactive ternary complex of the thiol-Hg-Se type, which does not inhibit delta-ALA-D.
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Affiliation(s)
- M Farina
- Curso de Farmácia, Centro de Ciências da Saúde, Universidade Regional Integrada-Campus de Erechim, 99700-000, Erechim RS, Brazil.
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Farina M, Brandão R, de Lara FS, Pagliosa LB, Soares FA, Souza DO, Rocha JBT. Profile of nonprotein thiols, lipid peroxidation and delta-aminolevulinate dehydratase activity in mouse kidney and liver in response to acute exposure to mercuric chloride and sodium selenite. Toxicology 2003; 184:179-87. [PMID: 12499120 DOI: 10.1016/s0300-483x(02)00576-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The effects of mercury (Hg(2+)) and selenite (Se(4+)) on delta-aminolevulinic acid dehydratase (delta-ALA-D) activity, 2-thiobarbituric acid reactive substances (TBARS) and nonprotein sulfhydryl content (NPSH) in mouse kidney and liver were investigated. Male mice were given a single i.p. injection of Hg(2+) and/or Se(4+) (25 micromol/kg) and were killed at 6, 12, 24 and 48 h after treatment. Hg(2+) inhibited renal delta-ALA-D at 6 and 12 h after treatment. Se(4+) abolished the inhibitory effect of mercury on renal delta-ALA-D at 12 h after treatment. Renal and hepatic NPSH content decreased after Hg(2+) exposure and selenite inhibited, at least in part, the Hg-induced oxidation of renal and hepatic NPSH. Se(4+) and Hg(2+), when injected alone, did not alter hepatic or renal TBARS levels; however, simultaneous exposure to these compounds increased hepatic and renal TBARS levels at 12 and 48 h after treatment, respectively. Present results suggest that selenium abolishes the interaction of Hg(2+) with sulfhydryl groups of protein and nonprotein sources.
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Affiliation(s)
- Marcelo Farina
- Curso de Farmácia, Centro de Ciências da Saúde, Universidade Regional Integrada do Alto Uruguai e Missões, Campus de Erechim, RS, Brazil.
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Nogueira CW, Soares FA, Nascimento PC, Muller D, Rocha JBT. 2,3-Dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase mercury- and cadmium-induced inhibition of delta-aminolevulinate dehydratase. Toxicology 2003; 184:85-95. [PMID: 12499112 DOI: 10.1016/s0300-483x(02)00575-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Compounds derived from Dimercaprol, such as meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercaptopropane-1-sulfonic acid (DMPS), are becoming common agents for treating humans exposed to heavy metals. Heavy metals such as Pb(2+), Hg(2+) and Cd(2+) can inhibit delta-aminolevulinate dehydratase (delta-ALA-D) activity. Delta-ALA-D catalyzes the condensation of two delta-aminolevulinic acid (delta-ALA) molecules with the formation of porphobilinogen, a heme precursor. The effects of DMSA and DMPS alone or in combination with Cd(2+), Hg(2+), or Pb(2+) on hepatic delta-ALA-D were examined. DMPS and DMSA caused a dose-dependent inhibition of hepatic delta-ALA-D. In the presence of Hg(2+) or Cd(2+) the inhibitory potency of DMPS increased. Similarly, the inhibitory effects of Hg(2+) and Cd(2+) were markedly increased in the presence of DMSA. In contrast, the inhibitory effect of DMPS was not changed by inclusion of Pb(2+). As observed with DMSA, Zn(2+) did not modified the inhibitory effect of DMPS. Data of the present report support the idea that the complexes formed (metals-DMSA or DMPS) were more inhibitory than the metal (Hg(2+) and Cd(2+)) or the chelating agent alone to the hepatic delta-ALA-D activity, in vitro. The mechanism of hepatic delta-ALA-D inhibition by Hg(2+)-DMPS/DMSA and Cd(2+)-DMPS/DMSA complexes involve the essential thiol groups of the enzyme.
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Affiliation(s)
- C W Nogueira
- Departamento de Quimica, Centro de Ciencias Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
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Farina M, Barbosa NBV, Nogueira CW, Folmer V, Zeni G, Andrade LH, Braga AL, Rocha JBT. Reaction of diphenyl diselenide with hydrogen peroxide and inhibition of delta-aminolevulinate dehydratase from rat liver and cucumber leaves. Braz J Med Biol Res 2002; 35:623-31. [PMID: 12045826 DOI: 10.1590/s0100-879x2002000600001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The interaction of the product of H2O2 and (PhSe)2 with delta-aminolevulinate dehydratase (delta-ALA-D) from mammals and plants was investigated. (PhSe)2 inhibited rat hepatic delta-ALA-D with an IC50 of 10 microM but not the enzyme from cucumber leaves. The reaction of (PhSe)2 with H2O2 for 1 h increased the inhibitory potency of the original compound and the IC50 for animal delta-ALA-D inhibition was decreased from 10 to 2 microM. Delta-ALA-D from cucumber leaves was also inhibited by the products of reaction of (PhSe)2 with H2O2 with an IC50 of 4 microM. The major product of reaction of (PhSe)2 with H2O2 was identified as seleninic acid and produced an intermediate with a (lambda)max at 265 nm after reaction with t-BuSH. These results suggest that the interaction of (PhSe)2 with mammal delta-ALA-D requires the presence of cysteinyl residues in close proximity. Two cysteine residues in spatial proximity have been recently described for the mammalian enzyme. Analysis of the primary structure of plant delta-ALA-D did not reveal an analogous site. In contrast to (PhSe)2, seleninic acid, as a result of the higher electrophilic nature of its selenium atom, may react with additional cysteinyl residue(s) in mammalian delta-ALA-D and also with cysteinyl residues from cucumber leaves located at a site distinct from that found at the B and A sites in mammals. Although the interaction of organochalcogens with H2O2 may have some antioxidant properties, the formation of seleninic acid as a product of this reaction may increase the toxicity of organic chalcogens such as (PhSe)2.
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Affiliation(s)
- M Farina
- Departamento de Química, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, Brasil
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Farina M, Folmer V, Bolzan RC, Andrade LH, Zeni G, Braga AL, Rocha JB. Selenoxides inhibit delta-aminolevulinic acid dehydratase. Toxicol Lett 2001; 119:27-37. [PMID: 11275419 DOI: 10.1016/s0378-4274(00)00296-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effect of two selenides and their selenoxides on delta-aminolevulinic acid dehydratase (delta-ALA-D) from liver of adult rats was investigated. In vivo, selenides can be oxidized to selenoxides by flavin-containing monooxygenases (FMO) and selenoxides can regenerate selenides by thiol oxidation. Phenyl methyl selenide (PhSeCH3) and 1-hexynyl methyl selenide (C4H9Ctriple bondCSeCH3) were converted to selenoxides by reaction with H2O2. PhSeCH3 and C4H9Ctriple bondCSeCH3 had no effect on delta-ALA-D up to 400 microM. Conversely, their selenoxides inhibited delta-ALA-D, and the IC(50) for enzyme inhibition was about 100 and 70 microM, respectively. Partially purified delta-ALA-D (P(55)) from swine liver was also inhibited by these selenoxides. The inhibitory action of selenoxides was antagonized by dithiotreitol (DTT). Moreover, delta-ALA-D from a plant source was inhibited by the selenoxides, suggesting a possible involvement of SH groups in a distinct site of the homologous region implicated in Zn2+ binding in mammalian delta-ALA-D. After exposure to PhSeCH3 (500 micromol/kg/day) for 45 or 30 days, the activity of delta-ALA-D from liver of mice decreased to about 50% of the control group. The in vivo inhibitory action of this compound was not antagonized by DTT. PhSeCH3 and C4H9Ctriple bondCSeCH3 had no effect on the rate of DTT oxidation, but their selenoxides oxidized DTT. The results of the present study suggest that hepatic delta-ALA-D of rodents is a potential molecular target for selenides as a consequence of their metabolism to selenoxides by FMO.
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Affiliation(s)
- M Farina
- Departamento de Química, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900, RS, Santa Maria, Brazil
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Petrovich RM, Litwin S, Jaffe EK. Bradyrhizobium japonicum porphobilinogen synthase uses two Mg(II) and monovalent cations. J Biol Chem 1996; 271:8692-9. [PMID: 8621501 DOI: 10.1074/jbc.271.15.8692] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Bradyrhizobium japonicum porphobilinogen synthase (B. japonicum PBGS) has been purified and characterized from an overexpression system in an Escherichia coli host (Chauhan, S., and O'Brian, M. R. (1995) J. Biol. Chem. 270, 19823-19827). B. japonicum PBGS defines a new class of PBGS protein, type IV (classified by metal ion content), which utilizes a catalytic MgA present at a stoichiometry of 4/octamer, an allosteric MgC present at a stoichiometry of 8/octamer, and a monovalent metal ion, K+. However, the divalent MgB or ZnB present in some other PBGS is not present in B. japonicum PBGS. Under optimal conditions, the Kd for MgA is <0.2 microM, and the Kd for MgC is about 40 microM. The response of B. japonicum PBGS activity to monovalent and divalent cations is mutually dependent and varies dramatically with pH. B. japonicum PBGS is also found to undergo a dynamic equilibrium between active multimeric species and inactive monomers under assay conditions, a kinetic characteristic not reported for other PBGSs. B. japonicum PBGS is the first PBGS that has been rigorously demonstrated to lack a catalytic ZnA. However, consistent with prior predictions, B. japonicum PBGS can bind Zn(II) (presumably as ZnA) at a stoichiometry of 4/octamer with a Kd of 200 microM; but this high concentration is outside a physiologically significant range.
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Affiliation(s)
- R M Petrovich
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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16
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Rhie G, Avissar YJ, Beale SI. Structure and expression of the Chlorobium vibrioforme hemB gene and characterization of its encoded enzyme, porphobilinogen synthase. J Biol Chem 1996; 271:8176-82. [PMID: 8626508 DOI: 10.1074/jbc.271.14.8176] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Plasmids containing DNA from the green photosynthetic bacterium Chlorobium vibrioforme complement a heme-requiring Escherichia coli hemB mutant that is deficient in porphobilinogen (PBG) synthase activity. PBG synthase activity was detected in extract of complemented cells but not in that of cells transformed with control plasmid. The sequence of the C. vibrioforme hemB gene predicts a HemB protein that contains 328 amino acids, has a molecular weight of 36,407, and is 53% identical to the homologous proteins of Synechocystis sp. PCC 6301 and Rhodobacter capsulatus. The response of C. vibrioforme PBG synthase to divalent metals is unlike that of any previously described PBG synthase; Mg2+ stimulates but is not required for activity, and Zn2+ neither stimulates nor is required. This response correlates with predicted sequences of two putative variable metal binding regions of C. vibrioforme HemB. The C. vibrioforme hemB open reading frame begins 1585 bases downstream from the end of the hemD open reading frame and is transcribed in the same direction as hemA, hemC, and hemD. However, hemB is not part of the same transcription unit as these genes, and the hemB transcript is approximately the same size as the hemB gene alone. Between hemD and hemB there is an intervening open reading frame that is oriented in the opposite direction and encodes a protein with a predicted amino acid sequence significantly similar to that of inositol monophosphatase, an enzyme that is not involved in tetrapyrrole biosynthesis. The gene order within hem gene clusters is highly conserved in phylogenetically diverse prokaryotic organisms. This conservation suggests that there are functional constraints on the relative order of the hem genes.
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Affiliation(s)
- G Rhie
- Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912, USA
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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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Abstract
Porphobilinogen is the monopyrrole precursor of all biological tetrapyrroles. The biosynthesis of porphobilinogen involves the asymmetric condensation of two molecules of 5-aminolevulinate and is carried out by the enzyme porphobilinogen synthase (PBGS), also known as 5-aminolevulinate dehydratase. This review documents what is known about the mechanism of the PBGS-catalyzed reaction. The metal ion constituents of PBGS are of particular interest because PBGS is a primary target for the environmental toxin lead. Mammalian PBGS contains two zinc ions at each active site. Bacterial and plant PBGS use a third metal ion, magnesium, as an allosteric activator. In addition, some bacterial and plant PBGS may use magnesium in place of one or both of the zinc ions of mammalian PBGS. These phylogenetic variations in metal ion usage are described along with a proposed rationale for the evolutionary divergence in metal ion usage. Finally, I describe what is known about the structure of PBGS, an enzyme which has as yet eluded crystal structure determination.
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Affiliation(s)
- E K Jaffe
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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Abstract
The haem biosynthesis pathway continues to provide surprises, from the first enzyme, 5-aminolaevulinic acid synthase, the mRNA of which contains an iron-responsive element, to the last, ferrochelatase, that contains an iron sulphur cluster. 5-Aminolaevulinate dehydratase from animals are zinc-dependent enzymes while those from plants require magnesium. The first X-ray structure of a haem synthesis enzyme, porphobilinogen deaminase, has not only yielded clues about the mechanism of tetrapyrrole assembly but has also provided insight into the molecular basis of the human disease acute intermittent porphyria. Evidence is growing to suggest that a previously unsuspected alternative haem pathway may exist.
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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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