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Benabent M, Vilanova E, Mangas I, Sogorb MÁ, Estévez J. Interaction between substrates suggests a relationship between organophosphorus-sensitive phenylvalerate- and acetylcholine-hydrolyzing activities in chicken brain. Toxicol Lett 2014; 230:132-8. [PMID: 24576786 DOI: 10.1016/j.toxlet.2014.02.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 02/13/2014] [Accepted: 02/17/2014] [Indexed: 10/25/2022]
Abstract
Organophosphorus compounds (OPs) induce neurotoxic disorders through interactions with well-known target esterases, such as acetylcholinesterase and neuropathy target esterase (NTE). However, OPs interact with other esterases of unknown biological function. In soluble chicken brain fractions, three components of enzymatic phenylvalerate esterase activity (PVase) called Eα, Eβ and Eγ, have been kinetically discriminated. These components are studied in this work for the relationship with acetylcholine-hydrolyzing activity. When Eα PVase activity (resistant PVase activity to 1500 μM PMSF for 30 min) was tested with different acetylthiocholine concentrations, inhibition was observed. The best-fitting model to the data was the non-competitive inhibition model (Km=0.12, 0.22 mM, Ki=6.6, 7.6 mM). Resistant acetylthiocholine-hydrolyzing activity to 1500 μM PMSF was inhibited by phenylvalerate showing competitive inhibition (Km=0.09, 0.11 mM; Ki=1.7, 2.2 mM). Eβ PVase activity (resistant PVase activity to 25 μM mipafox for 30 min) was not affected by the presence of acetylthiocholine, while resistant acetylthiocholine-hydrolyzing activity to 25 μM mipafox showed competitive inhibition in the presence of phenylvalerate (Km=0.05, 0.06 mM; Ki=0.44, 0.58 mM). The interactions observed between the substrates of AChE and PVase suggest that part of PVase activity might be a protein with acetylthiocholine-hydrolyzing activity.
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Affiliation(s)
- Mónica Benabent
- University "Miguel Hernandez", Institute of Bioengineering, Unit of Toxicology, Elche, Spain
| | - Eugenio Vilanova
- University "Miguel Hernandez", Institute of Bioengineering, Unit of Toxicology, Elche, Spain
| | - Iris Mangas
- University "Miguel Hernandez", Institute of Bioengineering, Unit of Toxicology, Elche, Spain
| | - Miguel Ángel Sogorb
- University "Miguel Hernandez", Institute of Bioengineering, Unit of Toxicology, Elche, Spain
| | - Jorge Estévez
- University "Miguel Hernandez", Institute of Bioengineering, Unit of Toxicology, Elche, Spain.
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Jósê AS, Franciscato C, Sônego F, Figueiró M, Thiesen FV, Garcia SC, Pereira ME. Sensitivity of young rats to nicotine exposure: Physiological and biochemical parameters. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2009; 72:242-247. [PMID: 18462794 DOI: 10.1016/j.ecoenv.2008.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Revised: 03/10/2008] [Accepted: 03/23/2008] [Indexed: 05/26/2023]
Abstract
This work has investigated the effects of prolonged exposure of young rats to nicotine on some physiological and biochemical parameters. Wistar male rats (30 days old) were treated (s.c.) with saline or nicotine 5mg/kg/day for 28 or 56 days. They received five injections (1mg/kg) per day (8, 10, 12:00 a.m., 2 and 4:00 p.m.) on the dark period of the cycle. Nicotine exposure for 56 days reduced body and liver weights. Moreover, nicotine exposure for 28 or 56 days decreased the hepatic glycogen but not blood glucose levels. The activities of blood and hepatic PBG-synthase, and blood and cerebral acetylcholinesterase were not affected by in vivo exposure. However, these activities were inhibited by nicotine in vitro. Results show that although high levels of plasma cotinine were found in both intervals of exposures, the parameters here analyzed were not affected by prolonged nicotine exposure except the storage of glucose, and body and liver weights.
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Affiliation(s)
- A S Jósê
- Programa de Pós-Graduação em Bioquímica Toxicológica, Brazil
| | - C Franciscato
- Programa de Pós-Graduação em Bioquímica Toxicológica, Brazil
| | - F Sônego
- Departamento de Química, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
| | - M Figueiró
- Programa de Pós-Graduação em Bioquímica Toxicológica, Brazil
| | - F V Thiesen
- Faculdade de Farmácia, Pontifícia Universidade Católica do Rio Grande do Sul, 90619-900 Porto Alegre, RS, Brazil
| | - S C Garcia
- Departamento de Análises Clínicas e Toxicológicas, CSS, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
| | - M E Pereira
- Programa de Pós-Graduação em Bioquímica Toxicológica, Brazil; Departamento de Química, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil.
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Kamal MA, Al-jafari AA. Kinetic constants for the inhibition of camel retinal acetylcholinesterase by the carbamate insecticide lannate. J Biochem Mol Toxicol 2000; 13:41-6. [PMID: 9890446 DOI: 10.1002/(sici)1099-0461(1999)13:1<41::aid-jbt5>3.0.co;2-f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We have designed this study to determine various kinetic parameters of camel retinal membrane-bound acetylcholinesterase (AChE; EC 3.1.1.7) inhibition by carbamate insecticide lannate [methyl N-[[(methylamino)carbonyl]oxy] ethanimidothioate]. All these kinetic constants were derived by simple graphical methods. The value of kinetic parameters was estimated as follows: 0.061 microM)(-1), 1.14 (microM)(-1), 0.216 microM, 0.016 min(-1), 0.0741 (gammaM min)(-1) 0.746 microM, and 4.42 microM for velocity constant (Kv), new inhibition constant (Knic), dissociation constant (Kd), carbamylation rate constant (k2c), overall carbamylation rate constant (k'2), 50% inhibition constant (K150), and 99% inhibition constant (K199), respectively. These unique methods may be used to estimate such kinetic parameters for time-dependent inhibition of enzymes by variety of chemicals, insecticides, herbicides, and drugs.
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Affiliation(s)
- M A Kamal
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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Kamal MA, Nasim FH, Al-Jafari AA. Human erythrocyte acetylcholinesterase inhibition by cis-diamminediaquaplatinum (II): a novel kinetic approach. Cancer Lett 1999; 138:115-9. [PMID: 10378782 DOI: 10.1016/s0304-3835(98)00385-1] [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: 11/24/2022]
Abstract
The present work addresses the analyses of some novel kinetic parameters (k(t), K(v), t50, K(ir), t(c), m(c), IC50, IC99 and Ki) of human erythrocyte membrane-bound acetylcholinesterase (AChE, EC 3.1.1.7) inhibition by cis-diamminediaquaplatinum II (PDC). PDC is under a clinical trial for use as an antineoplastic drug. The authors recently reported that PDC and cisplatin have the ability to inhibit AChE activity in vitro. Therefore this study was designed to determine the estimation of time constant (k(t)), velocity constant (K(v)), 50% inhibition time (t50), inhibition rate constant (K(ir)), transition concentration (t(c)), meeting concentration (m(c)), 50% inhibition (IC50), 99% inhibition (IC99) and inhibition constant (Ki) by novel methods. The details are described in the text.
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Affiliation(s)
- M A Kamal
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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Alhomida AS, Kamal MA, al-Jafari AA. Evaluation of the nature of camel retinal acetylcholinesterase: inhibition by hexamethonium. JOURNAL OF ENZYME INHIBITION 1997; 12:303-11. [PMID: 9502051 DOI: 10.3109/14756369709035822] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Acetylcholinesterase (AChE, EC 3.1.1.7) has been demonstrated in retinas of several species, however, the nature of the interaction of AChE with specific inhibitors are very limited in the literature and the mode of inhibition of camel retinal AChE by hexamethonium has been studied. Hexamethonium reversibly inhibited AChE in a concentration dependent manner, the IC50 value being c. 2.52 mM. The Km for the hydrolysis of acetylthiocholine iodide was found to be 0.087 mM and the Vmax was 0.63 mumol/min/mg protein. Dixon, as well as Lineweaver-Burk, plots and their secondary replots indicated that the nature of the inhibition is of the hyperbolic (partial) mixed type, which is considered to be a partial competitive and non-competitive mixture. The values of Ki(slope) and KI(intercept) from a Lineweaver-Burk plot were estimated as 0.30 mM and 0.17 mM, respectively, while Ki from a Dixon plot was estimated as 0.725 mM. The Ki was greater than KI indicating that hexamethonium has a greater affinity of binding for the active site than the peripheral site of the camel retina AChE.
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Affiliation(s)
- A S Alhomida
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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al-Jafari AA, Kamal MA, Alhomida AS. Thermodynamic investigation of camel retina acetylcholinesterase inhibition by cyclophosphamide. JOURNAL OF ENZYME INHIBITION 1997; 11:275-83. [PMID: 9208370 DOI: 10.3109/14756369709027656] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The present work addresses the estimation of energy parameters such as Gibb's free energy change (delta G), enthalpy change (delta H); entropy change (delta S) and activation energy (E a) of acetylcholinesterase (AChE, EC 3.1.1.7) from camel retina in the absence and presence of the antineoplastic drug cyclophosphamide (CP). A spectrophotometric method was used for the determination of AChE activity, which was the basis for determination of these parameters. The PZ factor (number of sterically and energetically favorable collisions occurring between CP and AChE) have also been studied in this investigation. The energy parameters obtained in the present investigation were compared with the values reported elsewhere.
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Affiliation(s)
- A A al-Jafari
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia.
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al-Khwyter F, Kamal MA, al-Jafari AA. The inhibitory effect of cyclophosphamide on camel retina acetylcholinesterase activity. Toxicol Lett 1996; 87:69-76. [PMID: 8914613 DOI: 10.1016/0378-4274(96)03706-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Kinetic parameters for the effect of cyclophosphamide (CP) on the camel retina acetylcholinesterase (AChE) activity were investigated for the first time in the present study. It was found that 18 micrograms of retina protein and an incubation time of 4.0 min were suitable conditions for linear of AChE activity. The CP effect was independent of time of incubation with AChE before the addition of substrate, which shows it reversible action. Moreover, dilution data prove that CP is a reversible inhibitor of camel retina AChE. Cyclophosphamide (0.2-2.4 mM) inhibited activity of camel retina in a concentration-dependent fashion, the IC50 being about 1.17 mM. The Michaelis constant (K(m)) for the hydrolysis of acetylthiocholine iodide was found to be 0.106 mM and the Vmax was 0.765 mumol/min/mg protein. Dixon as well as Lineweaver-Burk plots and their secondary replots indicated that the nature of the inhibition was of the pure noncompetitive type. The value of Ki was estimated as 0.763 mM by the primary Dixon and secondary replots of the Lineweaver-Burk plot.
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Affiliation(s)
- F al-Khwyter
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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Kamal MA, al-Jafari AA. The preparation and kinetic analysis of multiple forms of human erythrocyte acetylcholinesterase. Prep Biochem Biotechnol 1996; 26:105-19. [PMID: 8784921 DOI: 10.1080/10826069608000057] [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: 02/02/2023]
Abstract
A method for preparing various forms of acetylcholinesterase (AChE) from human erythrocyte has been established and they have been characterized in terms of kinetic parameters such as K(m), rate constant (k), turnover number (kcat), specificity constant (ksp), Vmax, half-life (t1/2), IC50 and Ki for tetrabutylammonium hydroxide, procaine and physostigmine in the present study. The solubility experiments show that, there is one major form of AChE i.e. membrane bound AChE (MBAChE) and one minor form i.e. water soluble form (WSAChE). The MBAChE shows several subforms, and on the basis of percentage activity only three MBAChE forms have been selected for complete characterization by various kinetic parameters and found that these three forms of MBAChE demonstrate significant differences in their kinetic properties except IC50. This study supports the recommendation of the use of these kinetic parameters as a tool for the analysis of the multiple forms of the various enzymes in the biological systems.
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Affiliation(s)
- M A Kamal
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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al-Jafari AA. The nature of the inhibition of camel retina acetylcholinesterase (EC 3.1.1.7) activity by tetrahydroaminoacridine. J Ocul Pharmacol Ther 1996; 12:503-14. [PMID: 8951687 DOI: 10.1089/jop.1996.12.503] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The nature of the inhibition of camel retina acetylcholinesterase (AChE) activity by tetrahydro-aminoacridine (THA, tacrine) has been investigated in the present study. The non-significant change of the percent inhibition of AChE by THA with respect to various lengths of the preincubation period showed the type of the reversible inhibition. THA reversibly inhibited AChE activity in a concentration dependent manner; IC50 was 0.23 microM while the IC100 was 14.22 microM. The K(m) for the hydrolysis of acetylthiocholine iodide was found to be 62.6 microM in the control system; a value increased in the THA treated systems. The Vmax was 0.472 mumole/min/mg protein for the control system, while it decreased in the THA treated systems. Dixon, as well as Lineweaver-Burk, plots and their secondary replots indicated that the nature of the inhibition is of the linear mixed type, which is considered to be a partial competitive and pure non-competitive mixture. The values of Ki(slope) and K'i(intercept) were estimated as 0.068 microM and 0.181 microM, respectively. The K'i was greater than Ki indicating that THA has a greater affinity of binding for the peripheral site than the active site of the camel retina AChE. The use of camel retina as a good experimental animal model may open new avenues for studying acetylcholine and AChE metabolism.
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Affiliation(s)
- A A al-Jafari
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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AlJafari AA, Kamal MA, Duhaiman AS, Alhomida AS. Acetylcholinesterase from desert cobra (Walterinnesia aegyptia) venom: optimization and kinetics study. Mol Cell Biochem 1995; 151:21-6. [PMID: 8584009 DOI: 10.1007/bf01076891] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Acetylcholinesterase (AChE) was investigated in Walterinnesia aegyptia venom and characterized with respect to its kinetic properties. It was found that 4.0 micrograms of crude venom protein and an incubation time of 4.0 min were suitable conditions for linearity of AChE activity at 25 degrees C. The optimum strength of the sodium phosphate buffer was 0.05 M, and the optimum pH was 7.75. The optimum temperature was 30 degrees C. The activation energy and the heat of activation were observed to be 6510 and 5922 cal/mole. The AChE was specific for acetylthiocholine but it did not hydrolyse butyrylthiocholine. The optimum substrate concentration was 3.0 mM but at higher substrate concentrations, the AChE activity declined. The ASCh concentration ranges for different orders of the reactions were determined and kinetic parameters (Km, Vmax, Kcat, and Ksp) were established at each order of the reaction.
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Affiliation(s)
- A A AlJafari
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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Al-Jafari AA, Duhaiman AS. Kinetics of the inhibition of acetylcholinesterase from pigeon brain by procaine hydrochloride. Cell Biochem Funct 1994. [DOI: 10.1002/cbf.290120309] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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