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Yasir M, Park J, Lee Y, Han ET, Park WS, Han JH, Kwon YS, Lee HJ, Chun W. Discovery of GABA Aminotransferase Inhibitors via Molecular Docking, Molecular Dynamic Simulation, and Biological Evaluation. Int J Mol Sci 2023; 24:16990. [PMID: 38069313 PMCID: PMC10707509 DOI: 10.3390/ijms242316990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 12/18/2023] Open
Abstract
γ-Aminobutyric acid aminotransferase (GABA-AT) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that degrades γ-aminobutyric (GABA) in the brain. GABA is an important inhibitory neurotransmitter that plays important neurological roles in the brain. Therefore, GABA-AT is an important drug target that regulates GABA levels. Novel and potent drug development to inhibit GABA-AT is still a very challenging task. In this study, we aimed to devise novel and potent inhibitors against GABA-AT using computer-aided drug design (CADD) tools. Since the crystal structure of human GABA-AT was not yet available, we utilized a homologous structure derived from our previously published paper. To identify highly potent compounds relative to vigabatrin, an FDA-approved drug against human GABA-AT, we developed a pharmacophore analysis protocol for 530,000 Korea Chemical Bank (KCB) compounds and selected the top 50 compounds for further screening. Preliminary biological analysis was carried out for these 50 compounds and 16 compounds were further assessed. Subsequently, molecular docking, molecular dynamics (MD) simulations, and binding free energy calculations were carried out. In the results, four predicted compounds, A07, B07, D08, and H08, were found to be highly potent and were further evaluated by a biological activity assay to confirm the results of the GABA-AT activity inhibition assay.
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Affiliation(s)
- Muhammad Yasir
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (M.Y.); (J.P.); (H.-J.L.)
| | - Jinyoung Park
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (M.Y.); (J.P.); (H.-J.L.)
| | - Yuno Lee
- Drug Information Platform Center, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea;
| | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (E.-T.H.); (J.-H.H.)
| | - Won Sun Park
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea;
| | - Jin-Hee Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (E.-T.H.); (J.-H.H.)
| | - Yong-Soo Kwon
- College of Pharmacy, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Hee-Jae Lee
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (M.Y.); (J.P.); (H.-J.L.)
| | - Wanjoo Chun
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (M.Y.); (J.P.); (H.-J.L.)
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Yasir M, Park J, Han ET, Park WS, Han JH, Kwon YS, Lee HJ, Chun W. Computational Exploration of the Effects of Mutations on GABA Aminotransferase in GABA Aminotransferase Deficiency. Int J Mol Sci 2023; 24:10933. [PMID: 37446113 DOI: 10.3390/ijms241310933] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 07/15/2023] Open
Abstract
Gamma-aminobutyric acid (GABA) transaminase-also called GABA aminotransferase (GABA-AT)-deficiency is a rare autosomal recessive disorder characterized by a severe neonatal-infantile epileptic encephalopathy with symptoms such as seizures, hypotonia, hyperreflexia, developmental delay, and growth acceleration. GABA transaminase deficiency is caused by mutations in GABA-AT, the enzyme responsible for the catabolism of GABA. Mutations in multiple locations on GABA-AT have been reported and their locations have been shown to influence the onset of the disease and the severity of symptoms. We examined how GABA-AT mutations influence the structural stability of the enzyme and GABA-binding affinity using computational methodologies such as molecular dynamics simulation and binding free energy calculation to understand the underlying mechanism through which GABA-AT mutations cause GABA-AT deficiency. GABA-AT 3D model depiction was carried out together with seven individual mutated models of GABA-AT. The structural stability of all the predicted models was analyzed using several tools and web servers. All models were evaluated based on their phytochemical values. Additionally, 100 ns MD simulation was carried out and the mutated models were evaluated using RMSD, RMSF, Rg, and SASA. gmxMMPBSA free energy calculation was carried out. Moreover, RMSD and free energy calculations were also compared with those obtained using online web servers. Our study demonstrates that P152S, Q296H, and R92Q play a more critical role in the structural instability of GABA-AT compared with the other mutated models: G465R, L211F, L478P, and R220K.
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Affiliation(s)
- Muhammad Yasir
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Jinyoung Park
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Won Sun Park
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Jin-Hee Han
- Department of Medical Environmental Biology and Tropical Medicine, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Yong-Soo Kwon
- College of Pharmacy, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Hee-Jae Lee
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
| | - Wanjoo Chun
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea
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Hamada Abd-Allah W, Abd El-Mohsen Anwar M, Mohammed ER, Elbaset MA, El Moghazy SM. Exploring new cyclohexane carboxamides based GABA agonist: Design, synthesis, biological evaluation, in silico ADME and docking studies. Bioorg Chem 2023; 136:106561. [PMID: 37119786 DOI: 10.1016/j.bioorg.2023.106561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/16/2023] [Accepted: 04/19/2023] [Indexed: 05/01/2023]
Abstract
The new series of 5a-e, 6a-e and 7a-e derivatives were designed, synthesized and tested for their anticonvulsant activity using "gold standard methods" ScPTZ and MES model, neurotoxicity, liver enzymes and neurochemical assay. Screening of the synthesized analogues exhibited variable anticonvulsant potential especially in chemically induced seizures. Quantification study showed that compounds 6d and 6e were the most potent analogues with ED50 44.77 and 11.31 mg/kg, respectively in ScPTZ test. Compound 6e (0.031 mmol/kg) was about 2 fold more potent than phenobarbital (0.056 mmol/kg) and was 30 folds more potent than Ethosuximide (0.92 mmol/kg) as reference standard drug. Moreover, all the synthesized compounds were screened for acute neurotoxicity using the rotarod method to recognize motor impairment, whereas all compounds devoid from neurotoxicity except compound 5a, 5b, 7a and 7e. The most active compounds were examined for acute toxicity and the estimates for LD50 were stated. Further neurochemical study was performed to investigate the effect of the most active compounds in ScPTZ test on GABA level in brain of the mice; a significant elevation in GABA level was obvious for compound 6d compared to control group confirming GABAergic modulating activity. Docking study was accomplished to examine the binding interaction of the newly synthesized analogues with GABA-AT enzyme. Additionally, physicochemical and pharmacokinetic parameters were predicted. The attained results indicate that the newly target compounds are considered a promising scaffolds for further development of newly anticonvulsants.
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Affiliation(s)
- Walaa Hamada Abd-Allah
- Pharmaceutical Chemistry Department, Collage of Pharmaceutical Science and Drug Manufacturing, Misr University for Science and Technology, P.O. 77, 6th of October City, Giza, Egypt.
| | - Mostafa Abd El-Mohsen Anwar
- Pharmaceutical Chemistry Department, Collage of Pharmaceutical Science and Drug Manufacturing, Misr University for Science and Technology, P.O. 77, 6th of October City, Giza, Egypt
| | - Eman R Mohammed
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Cairo University, 11562 Cairo, Egypt
| | - Marawan A Elbaset
- Department of Pharmacology, Medical Research and Clinical Studies Institute, National Research Centre, Giza, Egypt
| | - Samir M El Moghazy
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Cairo University, 11562 Cairo, Egypt
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Feja M, Meller S, Deking LS, Kaczmarek E, During MJ, Silverman RB, Gernert M. OV329, a novel highly potent γ-aminobutyric acid aminotransferase inactivator, induces pronounced anticonvulsant effects in the pentylenetetrazole seizure threshold test and in amygdala-kindled rats. Epilepsia 2021; 62:3091-3104. [PMID: 34617595 DOI: 10.1111/epi.17090] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/23/2021] [Accepted: 09/23/2021] [Indexed: 11/29/2022]
Abstract
OBJECTIVE An attractive target to interfere with epileptic brain hyperexcitability is the enhancement of γ-aminobutyric acidergic (GABAergic) inhibition by inactivation of the GABA-metabolizing enzyme GABA aminotransferase (GABA-AT). GABA-AT inactivators were designed to control seizures by raising brain GABA levels. OV329, a novel drug candidate for the treatment of epilepsy and addiction, has been shown in vitro to be substantially more potent as a GABA-AT inactivator than vigabatrin, an antiseizure drug approved as an add-on therapy for adult patients with refractory complex partial seizures and monotherapy for pediatric patients with infantile spasms. Thus, we hypothesized that OV329 should produce pronounced anticonvulsant effects in two different rat seizure models. METHODS We therefore examined the effects of OV329 (5, 20, and 40 mg/kg ip) on the seizure threshold of female Wistar Unilever rats, using the timed intravenous pentylenetetrazole (ivPTZ) seizure threshold model as a seizure test particularly sensitive to GABA-potentiating manipulations, and amygdala-kindled rats as a model of difficult-to-treat temporal lobe epilepsy. RESULTS GABA-AT inactivation by OV329 clearly increased the threshold of both ivPTZ-induced and amygdala-kindled seizures. OV329 further showed a 30-fold greater anticonvulsant potency on ivPTZ-induced myoclonic jerks and clonic seizures compared to vigabatrin investigated previously. Notably, all rats were responsive to OV329 in both seizure models. SIGNIFICANCE These results reveal an anticonvulsant profile of OV329 that appears to be superior in both potency and efficacy to vigabatrin and highlight OV329 as a highly promising candidate for the treatment of seizures and pharmacoresistant epilepsies.
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Affiliation(s)
- Malte Feja
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany
| | - Sebastian Meller
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Lillian S Deking
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Edith Kaczmarek
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | | | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA.,Department of Pharmacology, Chemistry of Life Processes Institute, Northwestern University, Chicago, Illinois, USA
| | - Manuela Gernert
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany
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Al-Obaidi A, Elmezayen AD, Yelekçi K. Homology modeling of human GABA-AT and devise some novel and potent inhibitors via computer-aided drug design techniques. J Biomol Struct Dyn 2020; 39:4100-4110. [PMID: 32462974 DOI: 10.1080/07391102.2020.1774417] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
γ-aminobutyric acid aminotransferase (GABA-AT) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme which degrades γ-aminobutyric (GABA) in the brain. GABA is an important inhibitory neurotransmitter that plays important neurological roles in the brain. Therefore, GABA-AT is an important drug target which regulates the GABA level. Novel and potent drug development to inhibit GABA-AT is still very challenging task. In this study, we aimed to devise novel and potent inhibitors against GABA-AT using computer-aided drug design (CADD) tools. However, the human GABA-AT crystal structure is not available yet, and we built the 3D structure of human GABA-AT based on the crystal structure of pig's liver (Sus Scrofa) enzyme as a template. The generated model was validated with numerous tools such as ProSA and PROCHECK. A set of selected well-known inhibitors have been tested against the modeled GABA-AT. Molecular docking studies have been accomplished via application of Genetic Optimization for Ligand Docking (GOLD), Vina and Autodock 4.2 software to search for potent inhibitors. The best two candidate inhibitors have been computationally examined for absorption, distribution, metabolism, elimination and toxicity descriptors (ADMET) and Lipinski's rule of 5. Lastly, molecular dynamics (MD) simulations were carried out to inspect the ligands' binding mode and stability of the active site of human GABA-AT over time. The top ranked ligands exhibited reliable stability throughout the MD simulation. The selected compounds are promising candidates and might be tested experimentally for the inhibition of human GABA-AT enzyme. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Anas Al-Obaidi
- Department of Bioinformatics and Genetics, Faculty of Engineering and Natural Sciences, Kadir Has University, Istanbul, Turkey
| | - Ammar D Elmezayen
- Department of Bioinformatics and Genetics, Faculty of Engineering and Natural Sciences, Kadir Has University, Istanbul, Turkey
| | - Kemal Yelekçi
- Department of Bioinformatics and Genetics, Faculty of Engineering and Natural Sciences, Kadir Has University, Istanbul, Turkey
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Verma KK, Singh UK, Jain J. Design, Synthesis and Biological Activity of Some 4, 5-Disubstituted-2, 4- Dihydro-3H-1, 2, 4- Triazole-3-Thione Derivatives. Cent Nerv Syst Agents Med Chem 2020; 19:197-205. [PMID: 31749420 DOI: 10.2174/1871524919666190722144424] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 07/08/2019] [Accepted: 07/12/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND In the present study, 4, 5-disubstituted triazol-3-thione derivatives were synthesized and evaluated for anticonvulsant activity along with neurotoxicity determination. MATERIALS AND METHODS The synthesized compounds were characterized using FTIR, 1H-NMR and MS. The anticonvulsant activity was assessed by Maximal Electroshock (MES) test and subcutaneous Pentylenetetrazole (scPTZ) tests and neurotoxicity was assessed by rotarod test. Docking was also performed to study the interactions of compounds with LYS329 residue of gamma amino butyric acid aminotransferase (GABA-AT) using Autodock 4.2 software. RESULTS The compounds 7a and 9a with significant pharmacological activity were also found to interact with LYS329 residue of GABA-AT by H-bond with a docking score of -5.92 kcal/mol (Ki = 41.99 μM) and -5.87 kcal/mol (Ki = 49.83 μM) respectively. CONCLUSION Most of the compounds were found to be active in MES test but only seven showed protection in scPTZ test.
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Affiliation(s)
- Krishan Kumar Verma
- Department of Pharmacy, Ram-Eesh Institute of Vocational & Technical Education, Knowledge Park-I, Greater Noida, UP, India
| | - Umesh Kumar Singh
- Kherwal Department of Pharmacy, Swami Vivekanand Subharti University, Meerut Bypass, Meerut, UP, India
| | - Jainendra Jain
- Department of Pharmacy, Ram-Eesh Institute of Vocational & Technical Education, Knowledge Park-I, Greater Noida, UP, India
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Verma KK, Singh UK, Jain J. Screening of Some Novel 4, 5 Disubstituted 1, 2, 4-Triazole-3-thiones for Anticonvulsant Activity. Cent Nerv Syst Agents Med Chem 2019; 20:41-48. [PMID: 31814557 DOI: 10.2174/1871524919666191209103003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 11/22/2022]
Abstract
OBJECTIVE In the present study, we synthesized fifteen 4, 5-disubstituted 1, 2, 4-triazol- 3-thione derivatives and evaluated for anticonvulsant activity with neurotoxicity determination. METHODS The synthesized compounds were characterized using FTIR, 1H-NMR and MS. The molecular docking study was also performed to study the interactions of compounds with LYS329 residue of gamma amino butyric acid aminotransferase (GABA-AT) using Autodock 4.2 software. The anticonvulsant activity was assessed by maximal electroshock (MES) test and subcutaneous pentylenetetrazol (scPTZ) tests. The neurotoxicity was assessed by rotarod ataxia test. RESULTS In MES test, compounds 5a, 8a and 9a were found active at 100 mg/kg and five compounds were found active at 300 mg/kg dose after 1 hr of administration. After 4 hr of drug administration, only two compounds 8a and 9a exhibited protection at 100 mg/kg. In scPTZ test, three compounds 2a, 6a and 8a were found active at 100 mg/kg and 7a was active at 300 mg/kg after 1 hr of test drug administration. Most of the compounds were found active in MES test with 8a and 9a being the most active among all. In docking study, 2a was found to be best compound based on the binding energy of -6.5 kcal/mol and estimated inhibition constant of 17.2 µM. CONCLUSION Majority of synthesized compounds were found active in MES test, whereas only few were found to possess anti scPTZ activity. Among all compounds, only 14a caused motor coordination impairment in rotarod ataxia test at 300 mg/kg 1 hr duration.
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Affiliation(s)
- Krishan K Verma
- Department of Pharmacy, Ram-Eesh Institute of Vocational & Technical Education, Plot No. 3, Knowledge Park-I, Greater Noida, UP, India
| | - Umesh K Singh
- Kherwal Department of Pharmacy, Swami Vivekanand Subharti University, Meerut Bypass, Meerut, UP, India
| | - Jainendra Jain
- Department of Pharmacy, Ram-Eesh Institute of Vocational & Technical Education, Plot No. 3, Knowledge Park-I, Greater Noida, UP, India
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Sahu M, Siddiqui N, Sharma V, Wakode S. 5,6-Dihydropyrimidine-1(2H)-carbothioamides: Synthesis, in vitro GABA-AT screening, anticonvulsant activity and molecular modelling study. Bioorg Chem 2018; 77:56-67. [PMID: 29331765 DOI: 10.1016/j.bioorg.2017.12.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 12/26/2017] [Accepted: 12/30/2017] [Indexed: 12/12/2022]
Abstract
Even after considerable advances in the field of epilepsy treatment, convulsions are inefficiently controlled by standard drug therapy. Herein, a series of pyrimidine-carbothioamide derivatives 4(a-t) was designed as anticonvulsant agents by doing some important structural modifications in well-known anticonvulsant drugs. Two classical animal models were used for the in vivo anticonvulsant screening, maximum electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) models; followed by motor impairment study by rotarod method. The most active compound 4g effectively suppressed seizure effect in both the animal models with median doses of 15.6 mg/kg (MES ED50), 278.4 mg/kg (scPTZ ED50) and 534.4 mg/kg (TD50) with no sign of neurotoxicity. Furthermore, in vitro GABA-AT enzyme activity assay of 4g showed inhibitory potency (IC50) of 12.23 μM. The docking study also favored the animal studies.
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Affiliation(s)
- Meeta Sahu
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Education & Research (Formerly, Faculty of Pharmacy), Jamia Hamdard, New Delhi 110062, India
| | - Nadeem Siddiqui
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Education & Research (Formerly, Faculty of Pharmacy), Jamia Hamdard, New Delhi 110062, India.
| | - Vidushi Sharma
- Department of Pharmaceutical Chemistry, Delhi Institute of Pharmaceutical Sciences and Research (DIPSAR), Mehrauli-Badarpur Road, Pushp Vihar, Sector-3, New Delhi 110017, India
| | - Sharad Wakode
- Department of Pharmaceutical Chemistry, Delhi Institute of Pharmaceutical Sciences and Research (DIPSAR), Mehrauli-Badarpur Road, Pushp Vihar, Sector-3, New Delhi 110017, India
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Gökcan H, Monard G, Sungur Konuklar FA. Molecular dynamics simulations of apo, holo, and inactivator bound GABA-at reveal the role of active site residues in PLP dependent enzymes. Proteins 2016; 84:875-91. [PMID: 26800298 DOI: 10.1002/prot.24991] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 12/24/2015] [Accepted: 12/29/2015] [Indexed: 11/08/2022]
Abstract
The pyridoxal 5-phosphate (PLP) cofactor is a significant organic molecule in medicinal chemistry. It is often found covalently bound to lysine residues in proteins to form PLP dependent enzymes. An example of this family of PLP dependent enzymes is γ-aminobutyric acid aminotransferase (GABA-AT) which is responsible for the degradation of the neurotransmitter GABA. Its inhibition or inactivation can be used to prevent the reduction of GABA concentration in brain which is the source of several neurological disorders. As a test case for PLP dependent enzymes, we have performed molecular dynamics simulations of GABA-AT to reveal the roles of the protein residues and its cofactor. Three different states have been considered: the apoenzyme, the holoenzyme, and the inactive state obtained after the suicide inhibition by vigabatrin. Different protonation states have also been considered for PLP and two key active site residues: Asp298 and His190. Together, 24 independent molecular dynamics trajectories have been simulated for a cumulative total of 2.88 µs. Our results indicate that, unlike in aqueous solution, the PLP pyridine moiety is protonated in GABA-AT. This is a consequence of a pKa shift triggered by a strong charge-charge interaction with an ionic "diad" formed by Asp298 and His190 that would help the activation of the first half-reaction of the catalytic mechanism in GABA-AT: the conversion of PLP to free pyridoxamine phosphate (PMP). In addition, our MD simulations exhibit additional strong hydrogen bond networks between the protein and PLP: the phosphate group is held in place by the donation of at least three hydrogen bonds while the carbonyl oxygen of the pyridine ring interacts with Gln301; Phe181 forms a π-π stacking interaction with the pyridine ring and works as a gate keeper with the assistance of Val300. All these interactions are hypothesized to help maintain free PMP in place inside the protein active site to facilitate the second half-reaction in GABA-AT: the regeneration of PLP-bound GABA-AT (i.e., the holoenzyme). Proteins 2016; 84:875-891. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Hatice Gökcan
- Universite De Lorraine, UMR 7565 SRSMC, Boulevard Des Aiguillettes B.P. 70239, Vandoeuvre-les-Nancy, 54506, France.,CNRS, UMR 7565 SRSMC, Boulevard Des Aiguillettes B.P. 70239, Vandoeuvre-les-Nancy, 54506, France.,Computational Science and Engineering Division, Informatics Institute, Ayazağa Campus, Maslak, Istanbul, 34496, Turkey
| | - Gerald Monard
- Universite De Lorraine, UMR 7565 SRSMC, Boulevard Des Aiguillettes B.P. 70239, Vandoeuvre-les-Nancy, 54506, France.,CNRS, UMR 7565 SRSMC, Boulevard Des Aiguillettes B.P. 70239, Vandoeuvre-les-Nancy, 54506, France
| | - F Aylin Sungur Konuklar
- Computational Science and Engineering Division, Informatics Institute, Ayazağa Campus, Maslak, Istanbul, 34496, Turkey
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