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Turki M, Abidi O, Ellouze S, Ben Abdallah F, Youzbechi F, Halouani N, Aloulou J. Schizophrenia And Polycystic Ovary Syndrome: A Case Report. Eur Psychiatry 2022. [PMCID: PMC9567768 DOI: 10.1192/j.eurpsy.2022.2028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Introduction
Patients with Polycystic ovary syndrome (PCOS) have increased vulnerability to psychiatric disorders, particularly a tendency to depression and anxiety, as well as schizophrenia. The association between PCOS and psychiatric disorders is a topic of research given the possibility of common potential mechanisms as well as the clinical similarity between the adverse effects of atypical antipsychotics and the symptoms of PCOS.
Objectives
We proposed to investigate the etiopathogenic relationship between schizophrenia and PCOS as well as the therapeutic particularities.
Methods
We report a case of schizophrenia occurring in a patient with PCOS. Then, we conducted a literature review using “PubMed” database and keywords “psychosis”, “schizophrenia”, “Polycystic ovary syndrome” and “antipsychotic drugs”.
Results
She was an 18-year-old patient, diagnosed with PCOS since 2018. She has been followed in the psychiatry outpatient department since 8 months for psychotic symptoms (hallucinatory syndrome with thoughts of self-aggressiveness, delusional syndrome with mental automatism…). She was prescribed olanzapine (5 then 10 mg/day). However, after a weight gain (4 kg per month), this drug was switched by Risperidone (2 then 4 mg/day). The evolution was marked by the appearance of galactorrhea. Thus, the Risperidone was switched to Aripiprazole. Then, we noted a significant improvement on the psychiatric features and a better clinical tolerance.
Conclusions
For women with PCOS and psychosis, treatment with antipsychotic drugs can worsen PCOS symptomatology and lead to negative consequences for a woman’s reproductive potential and her quality of life. Therefore, the psychosis management must take these particularities into account, in order to improve the prognosis of both diseases.
Disclosure
No significant relationships.
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Turki M, Daoud A, Blanji S, Ellouze S, Ben Jmeaa R, Ben Abdallah F, Halouani N, Aloulou J. Factors Associated With The Covid-19 Infection Severity In Patients With Mental Disorders. Eur Psychiatry 2022. [PMCID: PMC9567294 DOI: 10.1192/j.eurpsy.2022.1304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Introduction
Recent research showed that persons with mental disorders may represent a population at increased risk for coronavirus disease (COVID-19) infection with more adverse outcomes.
Objectives
We aimed to analyze clinical profile of psychiatric inpatients during their infection with COVID-19, and to explore factors associated with the disease progression.
Methods
We analyzed retrospectively the medical records of 32 psychiatric inpatients, hospitalized in psychiatry “B” department at Hedi Chaker hospital (Sfax, Tunisia), and who contracted the COVID-19 infection. We used “Charlson Comorbidity Index Score” (CCIS), predicting 10-year survival in patients with multiple comorbidities.
Results
Somatic history was reported in 50% of patients. The CCIS ranged between 0 and 4. Psychiatric diagnosis was schizophrenia in 81.3% and bipolar disorder in 18.7% of cases. The clinical symptoms reported were fever (50%), dry cough (75%); dyspnea (34.4%). Biological assessment showed a lymphopenia in 40.6% and a high C-Reactive Protein (CRP) in 53.1%. Among our patients, 37,5% needed oxygen, and 25% were transferred to the intensive care unit. The COVID-19 complications were mostly bacterial pulmonary superinfections (21.9%) and pulmonary embolism (9.4%). Only three (9.4%) patients died from the virus. Patients with medical history were more likely to need oxygen (p<0.001). Clinical and paraclinical parameters associated with oxygen need were: fever (p<0.001); dyspnea (p<0.001); lymphopenia (p<0.001); high CRP (p=0.001). Patients presenting pulmonary superinfection or embolism were more likely to require oxygen (p=0.006 and p=0.044 respectively).
Conclusions
This study highlighted factors that may worsen the COVID-19 infection evolution, and which require special attention, in order to improve the prognosis of this disease.
Disclosure
No significant relationships.
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Zouari M, Ben Ahmed C, Zorrig W, Elloumi N, Rabhi M, Delmail D, Ben Rouina B, Labrousse P, Ben Abdallah F. Exogenous proline mediates alleviation of cadmium stress by promoting photosynthetic activity, water status and antioxidative enzymes activities of young date palm (Phoenix dactylifera L.). Ecotoxicol Environ Saf 2016; 128:100-8. [PMID: 26901506 DOI: 10.1016/j.ecoenv.2016.02.015] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 01/29/2016] [Accepted: 02/12/2016] [Indexed: 05/22/2023]
Abstract
The ability of exogenous compatible solutes, such as proline, to counteract cadmium (Cd) inhibitory effects in young date palm plants (Phoenix dactylifera L. cv Deglet Nour) was investigated. Two-year-old date palm plants were subjected for five months at different Cd stress levels (0, 10 and 30 mg CdCl2 kg(-1) soil) whether supplied or not with exogenous proline (20mM) added through the irrigation water. Different levels of Cd stress altered plant growth, gas exchanges and chlorophyll content as well as water status, but at different extent among them. In contrast, an increase of antioxidant enzymes activities of Cd-treated plants in association with high amounts of proline content, hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and electrolyte leakage (EL) were observed. Interestingly, exogenous proline mitigated the adverse effects of Cd on young date palm. Indeed, it alleviated the oxidative damage induced by Cd accumulation and established better levels of plant growth, water status and photosynthetic activity. Moreover, proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plants.
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Affiliation(s)
- M Zouari
- Laboratory of Plant Biodiversity and Dynamics of Ecosystems in Arid Area, Faculty of Sciences of Sfax, University of Sfax, Tunisia; Laboratory of Improvement of Olive Productivity and Fruit Trees, Olive Tree Institute of Sfax, Tunisia; University of Limoges, Faculty of Pharmacy, FR 3503 GEIST, GRESE EA 4330 - Laboratory of Botany and Cryptogamy, 87025 Limoges Cedex, France.
| | - Ch Ben Ahmed
- Laboratory of Plant Biodiversity and Dynamics of Ecosystems in Arid Area, Faculty of Sciences of Sfax, University of Sfax, Tunisia; Laboratory of Improvement of Olive Productivity and Fruit Trees, Olive Tree Institute of Sfax, Tunisia
| | - W Zorrig
- Laboratory of Extremophile Plants, Centre of Biotechnology of Borj-Cedria, Hammam-Lif, Tunisia
| | - N Elloumi
- Laboratory of Plant Biodiversity and Dynamics of Ecosystems in Arid Area, Faculty of Sciences of Sfax, University of Sfax, Tunisia
| | - M Rabhi
- Laboratory of Extremophile Plants, Centre of Biotechnology of Borj-Cedria, Hammam-Lif, Tunisia
| | - D Delmail
- Institute of Chemical Sciences of Rennes, CNRS UMR 6226, University of Rennes 1, 2 Avenue of Professor Léon Bernard, F-35043 Rennes, France
| | - B Ben Rouina
- Laboratory of Improvement of Olive Productivity and Fruit Trees, Olive Tree Institute of Sfax, Tunisia
| | - P Labrousse
- University of Limoges, Faculty of Pharmacy, FR 3503 GEIST, GRESE EA 4330 - Laboratory of Botany and Cryptogamy, 87025 Limoges Cedex, France.
| | - F Ben Abdallah
- Laboratory of Plant Biodiversity and Dynamics of Ecosystems in Arid Area, Faculty of Sciences of Sfax, University of Sfax, Tunisia
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Zouari M, Ben Ahmed C, Fourati R, Delmail D, Ben Rouina B, Labrousse P, Ben Abdallah F. Soil fluoride spiking effects on olive trees (Olea europaea L. cv. Chemlali). Ecotoxicol Environ Saf 2014; 108:78-83. [PMID: 25042248 DOI: 10.1016/j.ecoenv.2014.06.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 05/23/2014] [Accepted: 06/19/2014] [Indexed: 06/03/2023]
Abstract
A pot experiment under open air conditions was carried out to investigate the uptake, accumulation and toxicity effects of fluoride in olive trees (Olea europaea L.) grown in a soil spiked with inorganic sodium fluoride (NaF). Six different levels (0, 20, 40, 60, 80 and 100mM NaF) of soil spiking were applied through NaF to irrigation water. At the end of the experiment, total fluoride content in soil was 20 and 1770mgFkg(-1) soil in control and 100mM NaF treatments, respectively. The comparative distribution of fluoride partitioning among the different olive tree parts showed that the roots accumulated the most fluoride and olive fruits were minimally affected by soil NaF spiking as they had the lowest fluoride content. In fact, total fluoride concentration varied between 12 and 1070µgFg(-1) in roots, between 9 and 570µgFg(-1) in shoots, between 12 and 290µgFg(-1) in leaves, and between 10 and 29µgFg(-1) in fruits, respectively for control and 100mM NaF treatments. Indeed, the fluoride accumulation pattern showed the following distribution: roots>shoots>leaves>fruits. On the other hand, fluoride toxicity symptoms such as leaf necrosis and leaf drop appeared only in highly spiked soils (60, 80 and 100mM NaF).
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Affiliation(s)
- M Zouari
- Laboratory of Plant Biodiversity and Dynamic of Ecosystems in Arid Area, Faculty of Sciences of Sfax, B.P. 1171, Sfax 3000, Tunisia; Laboratory of Improvement of Olive Productivity and Fruit Trees, Olive Tree Institute of Sfax, B.P. 1087, Sfax 3018, Tunisia; University of Limoges, Faculty of Pharmacy, Laboratory of Botany and Cryptogamy, GRESE EA 4330, 2 rue du Docteur Marcland, F-87025 Limoges, France.
| | - C Ben Ahmed
- Laboratory of Plant Biodiversity and Dynamic of Ecosystems in Arid Area, Faculty of Sciences of Sfax, B.P. 1171, Sfax 3000, Tunisia; Laboratory of Improvement of Olive Productivity and Fruit Trees, Olive Tree Institute of Sfax, B.P. 1087, Sfax 3018, Tunisia
| | - R Fourati
- Laboratory of Plant Biodiversity and Dynamic of Ecosystems in Arid Area, Faculty of Sciences of Sfax, B.P. 1171, Sfax 3000, Tunisia
| | - D Delmail
- Institute of Chemical Sciences of Rennes, CNRS UMR 6226, University of Rennes, 2, Avenue of Professor Léon Bernard F-35043 RENNES Cedex, France
| | - B Ben Rouina
- Laboratory of Improvement of Olive Productivity and Fruit Trees, Olive Tree Institute of Sfax, B.P. 1087, Sfax 3018, Tunisia
| | - P Labrousse
- University of Limoges, Faculty of Pharmacy, Laboratory of Botany and Cryptogamy, GRESE EA 4330, 2 rue du Docteur Marcland, F-87025 Limoges, France.
| | - F Ben Abdallah
- Laboratory of Plant Biodiversity and Dynamic of Ecosystems in Arid Area, Faculty of Sciences of Sfax, B.P. 1171, Sfax 3000, Tunisia
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Ben Abdallah F, Msakni I, Yahia M, Laâbidi B, Moatamri Z, Bougrine F, Bouziani A. [Mixed papilloma: a case report]. Rev Pneumol Clin 2013; 69:303-305. [PMID: 24041973 DOI: 10.1016/j.pneumo.2013.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 03/18/2013] [Accepted: 03/26/2013] [Indexed: 06/02/2023]
Affiliation(s)
- F Ben Abdallah
- Service d'anatomie pathologique, hôpital militaire principal d'instructions de Tunis, Tunis, Tunisie.
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Ben Abdallah F, El Amine O, Goucha A, Ben Abdeljelil N, Debbabi B, Dhiab T, Ben Hassouna J, Rahal K, Gamoudi A. Le cancer du sein chez l’homme : à propos d’une série de 155 cas. Ann Pathol 2012. [DOI: 10.1016/j.annpat.2012.09.084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Ben Slima A, Ben Abdallah F, Keskes-Ammar L, Mallek Z, El Feki A, Gdoura R. Embryonic exposure to dimethoate and/or deltamethrin impairs sexual development and programs reproductive success in adult male offspring mice. Andrologia 2011; 44 Suppl 1:661-6. [DOI: 10.1111/j.1439-0272.2011.01246.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Ben Abdallah F, Fetoui H, Zribi N, Fakfakh F, Ammar-Keskes L. Antioxidant supplementations in vitro improve rat sperm parameters and enhance antioxidant enzyme activities against dimethoate-induced sperm damages. Andrologia 2011; 44 Suppl 1:272-9. [DOI: 10.1111/j.1439-0272.2011.01177.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Ben Abdallah F, Zribi N, Ammar-Keskes L. Antioxidative potential of Quercetin against hydrogen peroxide induced oxidative stress in spermatozoa in vitro. Andrologia 2011; 43:261-5. [DOI: 10.1111/j.1439-0272.2010.01063.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Abdallah FB, Hamden K, Galeraud-Denis I, El Feki A, Keskes-Ammar L. An in vitro study on reproductive toxicology of Deltamethrin on rat spermatozoa. Andrologia 2010; 42:254-9. [DOI: 10.1111/j.1439-0272.2009.00986.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Abdallah FB, Gargouri B, Lassoued S, Ammar-Keskes L. Dimethoate-induced oxidative stress in human erythrocytes and the protective effect of Vitamins C and E in vitro. Toxicol Lett 2010. [DOI: 10.1016/j.toxlet.2010.03.301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ben Abdallah F, Dammak I, Mallek Z, Attia H, Hentati B, Ammar-Keskes L. Effects of date seed oil on testicular antioxidant enzymes and epididymal sperm characteristics in male mice. Andrologia 2009; 41:229-34. [PMID: 19601934 DOI: 10.1111/j.1439-0272.2009.00923.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The aim of this study was to evaluate the effect of date seed oil (DSO) on epididymal sperm characteristics and testicular antioxidant enzymes in male mice. DSO was diluted into isotonic saline solution (0.9%) and different doses (5, 10, 15 and 20%) were prepared. Fifty male mice were divided into five groups; in four groups DSO was given by intraperitoneal injection of oil solution for 28 days. The control group was injected by isotonic saline solution without DSO. Body and reproductive organ weights, sperm characteristics (count, motility, viability and morphology) were assessed. In addition, levels of malondialdehyde (MDA), activities of superoxide dismutase (SOD) and catalase (CAT) were investigated in testes. A significant increase in sperm count, motility and viability of all treated animal groups was observed when compared with the control group (P < 0.05). Unlike, the percentage of abnormal sperm was significantly lower in all treated groups than in the control group (P < 0.05). A significant decrease in MDA levels and marked increase in SOD and CAT activities in mice treated with high doses of DSO (15 and 20%) were also noted. We suggest that DSO can improve the epididymal sperm quality and could ameliorate the testicular strategy defences.
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Affiliation(s)
- F Ben Abdallah
- Human Pathologies and oxidative stress unit, Superior Institute of Biotechnology of Sfax, Sfax, Tunisia.
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Ben Abdallah F, Chaieb K, Snoussi M, Bakhrouf A, Gaddour K. Phenotypic Variations and Molecular Identification of Salmonella enterica Serovar Typhimurium Cells Under Starvation in Seawater. Curr Microbiol 2007; 55:485-91. [PMID: 17828573 DOI: 10.1007/s00284-007-9017-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 06/07/2007] [Indexed: 11/28/2022]
Abstract
In seawater, enteric bacteria evolve toward a stressed state that is difficult to identify because of major alterations of their phenotype. In this study, we incubated four reference strains of S. enterica serovar Typhimurium in seawater microcosms for 10 months and studied the modifications of their main phenotypic characters. All of the strains lost some key characters used for traditional identification of the Salmonella genus. They became able to produce acetoin, and tryptophane deaminase activity became positive, but they lost the capacity to use rhamnose. We were able to show some modifications of the level of enzymatic profile as well as in their antibiotic susceptibility. The atypical cells of S. enterica serovar Typhimurium were identified by polymerase chain reaction (PCR) methods using the internal transcribed spacer region, and they were confirmed by multiplex PCR after the simultaneous amplification of the phoP, Hin, and H-li genes.
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Abstract
Iron loss in vitro by the iron scavenger bovine lactoferrin was investigated in acidic media in the presence of three different monoanions (NO(3)(-), Cl(-) and Br(-)) and one dianion (SO(4)(2-)). Holo and monoferric C-site lactoferrins lose iron in acidic media (pH< or =3.5) by a four-step mechanism. The first two steps describe modifications in the conformation affecting the whole protein, which occur also with apolactoferrin. These two processes are independent of iron load and are followed by a third step consisting of the gain of two protons. This third step is kinetically controlled by the interaction with two Cl(-), Br(-) and NO(3)(-) or one SO(4)(2-). In the fourth step, iron loss is under the kinetic control of a slow gain of two protons; third-order rate-constants k(2), 4.3(+/-0.2)x10(3), 3.4(+/-0.5)x10(3), 3.3(+/-0.5)x10(3) and 1.5(+/-0.5)x10(3) M(-2) s(-1) when the protein is in interaction with SO(4)(2-), NO(3)(-), Cl(-) or Br(-), respectively. This step is accompanied by the loss of the interaction with the anions; equilibrium constant K(2), 20+/-5 mM, 1.0(+/-0.2)x10(-1), 1.5(+/-0.5)x10(-1) and 1.0(+/-0.3)x10(-1) M(2), for SO(4)(-), NO(3)(-), Cl(-) and Br(-), respectively. This mechanism is very different from that determined in mildly acidic media at low ionic strength (micro<0.5) for the iron transport proteins, serum transferrin and ovotransferrin, with which no prior change in conformation or interaction with anions is required. These differences may result from the fact that in the transport proteins, the interdomain hydrogen bonds that consolidate the closed conformation of the iron-binding cleft occur between amino acid side-chain residues that can protonate in mildly acidic media. With bovine lactoferrin, most of the interdomain hydrogen bonds involved in the C-site and one of those involved in the N-site occur between amino acid side-chain residues that cannot protonate. The breaking of the interdomain H-bond upon protonation can trigger the opening of the iron cleft, facilitating iron loss in serum transferrin and ovotransferrin. This situation is, however, different in lactoferrin, where iron loss requires a prior change in conformation. This can explain why lactoferrin does not lose its iron load in acidic media and why it is not involved in iron transport in acidic endosomes.
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Affiliation(s)
- F B Abdallah
- Institut de Topologie et de Dynamique des Systèmes de l'Université Denis Diderot Paris 7, associé au CNRS, 1 rue Guy de la Brosse, 75005 Paris, France
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Pakdaman R, Abdallah FB, El Hage Chahine JM. Transferrin, is a mixed chelate-protein ternary complex involved in the mechanism of iron uptake by serum-transferrin in vitro? J Mol Biol 1999; 293:1273-84. [PMID: 10547300 DOI: 10.1006/jmbi.1999.3238] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Iron uptake by transferrin from triacetohydroxamatoFe(III) (Fe(AHA)3) in the presence of bicarbonate has been investigated between pH 7 and 8.2. The protein transits from the opened apo- to the closed holoform by several steps with the accumulation of at least three kinetic intermediates. All these steps are accompanied by proton losses, probably occurring from the protein ligands and the side-chains involved in the interdomain H-bonding nets. The minor bihydroxamatoFe(III) species Fe(AHA)2 exchanges its iron with the C-site of apotransferrin in interaction with bicarbonate without detectable formation of any intermediate protein-iron-ligand mixed complex; direct second-order rate constant k1=4.15(+/-0.05)x10(7) M(-1) s(-1). The kinetic product loses a single proton and undergoes a modification in its conformation followed by the loss of two or three protons; first-order rate constant k2=3.25(+/-0.15) s(-1). This induces a new modification in the conformation; first-order rate constant k3=5.90(+/-0.30)x10(-2) s(-1). This new modification in conformation rate controls iron uptake by the N-site of the protein and is followed by a single proton loss; K3a=6.80 nM. Finally, the holoprotein or the monoferric transferrin in its thermodynamic equilibrated state is produced by a last modification in the conformation occurring in about 4000 seconds. But for the Fe(AHA)3 dissociation and the involvement of Fe(AHA)2 in the first step of iron uptake, this mechanism is identical to that reported for iron uptake from FeNAc3. This implies that the exchange of iron between a chelate and serum-transferrin occurs by a single general mechanism. The nature of the iron-providing chelate is only important for the first kinetic step of the exchange, which can be slowed to such an extent that it rate limits the exchange of iron.
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Affiliation(s)
- R Pakdaman
- Institut de Topologie et de Dynamique des Systèmes de l'Université Denis Diderot Paris 7, associé au CNRS, 1 rue Guy de la Brosse, Paris, 75005, France
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Abstract
Iron release from ovotransferrin in acidic media (3 < pH < 6) occurs in at least six kinetic steps. The first is a very fast (</= 5 ms) decarbonation of the iron-loaded protein. Iron release from both sites of the protein is controlled by what appear to be slow proton transfers. The N-site loses its iron first in two steps, the first occurring in the tenth of a second range with second order rate constant k1 = (2.30 +/- 0.10) x 104 M-1.s-1, first order rate constant k-1 = (1.40 +/- 0.10) s-1 and equilibrium constant K1a = (60 +/- 6) microM. The second step occurs in the second range with a second order rate constant k2 = (5.2 +/- 0.15) x 103 M-1.s-1, first order rate constant k-2 = (0.2 +/- 0.02) s-1 and equilibrium constant K2a = (39 +/- 5) microM. Iron is afterward lost from the C-site of the protein by two different pathways, one in the presence of a strong Fe(III) ligand such as citrate and the other in the presence of weak ligands such as formate or acetate. The first step, common to both paths, is a slow proton uptake which occurs in the tens of second range with a second order rate constant k3 = (1.22 +/- 0.03) x 103 M-1.s-1 and equilibrium constant K3a = (1.0 +/- 0.1) mM. In the presence of citrate, this step is followed by formation of an intermediate complex with monoferric ovotransferrin; stability constant KLC = (0.435 +/- 0.015) mM. This last step is rate-controlled by slow proton gain which occurs in the hundred second range with a second order rate constant k4 = (1.05 +/- 0.05) x 104 M-1.s-1, first order rate constant k-4 = (1.0 +/- 0.1) x 10-2 s-1 and equilibrium constant K4a = (0.95 +/- 0.15) microM. In the presence of a weak iron(III) ligand such as acetate or formate, formation of an intermediate complex is not detected and iron release is controlled by two final slow proton uptakes. The first occurs in the hundred to thousand second range, second order rate constant k5 = (6.90 +/- 0.30) x 106 M-1.s-1. The last step occurs in the thousand second range. Iron release by ovotransferrin is similar but not identical to that of serum-transferrin. It is slower and occurs at lower pH values. However, as seen for serum-transferrin, it seems to involve the protonation of the amino acid side-chains involved in iron co-ordination and perhaps those implicated in interdomain H-bonds. The observed proton transfers are, then, probably controlled by the change in conformation of the binding lobes from closed when iron-loaded to open in the apo-form.
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Affiliation(s)
- F B Abdallah
- Institut de Topologie et de Dynamique des Systèmes, l'Université Denis Diderot Paris 7 associé au CNRS, Paris, France
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