1
|
Altamirano‐Espino JA, Córdova‐Moreno R, Andrade‐Jorge E, Martínez‐Archundia M, García‐Machorro J, Trujillo‐Ferrara JG. Design, Docking Simulations, Synthesis, and in vitro and in vivo Behavioral Assessment of
m
‐Aminobenzoic Acid Analogues as GABA‐AT Inhibitors. ChemistrySelect 2021. [DOI: 10.1002/slct.202102643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- José A. Altamirano‐Espino
- Laboratorio de Investigación en Bioquímica Sección de Estudios de Posgrado e Investigación Escuela Superior de Medicina del Instituto Politécnico Nacional Plan de San Luis y Díaz Mirón s/n Casco de Santo Tomás 11340 Mexico City México
| | - Rebeca Córdova‐Moreno
- Departamento de Sistemas Biológicos Universidad Autónoma Metropolitana-Unidad Xochimilco Mexico City 04960 México
| | - Erik Andrade‐Jorge
- Laboratorio de Investigación en Bioquímica Sección de Estudios de Posgrado e Investigación Escuela Superior de Medicina del Instituto Politécnico Nacional Plan de San Luis y Díaz Mirón s/n Casco de Santo Tomás 11340 Mexico City México
- Unidad de Investigación en Biomedicina y Carrera de enfermería Facultad de Estudios Superiores-Iztacala Universidad Nacional Autónoma de México Av. de los Barrios 1, Los Reyes Iztacala Tlalnepantla 54090, Estado de México México
| | - Marlet Martínez‐Archundia
- Laboratorio de Modelado Molecular Bioinformática y Diseño de Fármacos, y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina del Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón s/n 11340 Mexico City México
| | - Jazmín García‐Machorro
- Laboratorio de Medicina de Conservación, Escuela Superior de Medicina Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón Mexico City 11340 México
| | - José G. Trujillo‐Ferrara
- Laboratorio de Investigación en Bioquímica Sección de Estudios de Posgrado e Investigación Escuela Superior de Medicina del Instituto Politécnico Nacional Plan de San Luis y Díaz Mirón s/n Casco de Santo Tomás 11340 Mexico City México
| |
Collapse
|
2
|
Chen L, Wang Y, Chen Z. Adult Neurogenesis in Epileptogenesis: An Update for Preclinical Finding and Potential Clinical Translation. Curr Neuropharmacol 2021; 18:464-484. [PMID: 31744451 PMCID: PMC7457402 DOI: 10.2174/1570159x17666191118142314] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 10/31/2019] [Accepted: 11/18/2019] [Indexed: 12/22/2022] Open
Abstract
Epileptogenesis refers to the process in which a normal brain becomes epileptic, and is characterized by hypersynchronous spontaneous recurrent seizures involving a complex epileptogenic network. Current available pharmacological treatment of epilepsy is generally symptomatic in controlling seizures but is not disease-modifying in epileptogenesis. Cumulative evidence suggests that adult neurogenesis, specifically in the subgranular zone of the hippocampal dentate gyrus, is crucial in epileptogenesis. In this review, we describe the pathological changes that occur in adult neurogenesis in the epileptic brain and how adult neurogenesis is involved in epileptogenesis through different interventions. This is followed by a discussion of some of the molecular signaling pathways involved in regulating adult neurogenesis, which could be potential druggable targets for epileptogenesis. Finally, we provide perspectives on some possible research directions for future studies.
Collapse
Affiliation(s)
- Liying Chen
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yi Wang
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Epilepsy Center, Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology & Toxicology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Epilepsy Center, Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.,College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, China
| |
Collapse
|
3
|
Wang Y, Chen Z. An update for epilepsy research and antiepileptic drug development: Toward precise circuit therapy. Pharmacol Ther 2019; 201:77-93. [PMID: 31128154 DOI: 10.1016/j.pharmthera.2019.05.010] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 05/07/2019] [Indexed: 12/14/2022]
Abstract
Epilepsy involves neuronal dysfunction at molecular, cellular, and circuit levels. The understanding of the mechanism of the epilepsies has advanced greatly in the last three decades, especially in terms of their cellular and molecular basis. However, despite the availability of ~30 anti-epileptic drugs (AEDs) with diverse molecular targets, there are still many challenges (e.g. drug resistance, side effects) in pharmacological treatment of epilepsies today. Because molecular mechanisms are integrated at the level of neuronal circuits, we suggest a shift in epilepsy treatment and research strategies from the "molecular" level to the "circuit" level. Recent technological advances have facilitated circuit mechanistic discovery at each level and have paved the way for many opportunities of novel therapeutic strategies and AED development toward precise circuit therapy.
Collapse
Affiliation(s)
- Yi Wang
- Institute of Pharmacology and Toxicology, Department of Pharmacology, NHC and CAMS Key Laboratory of Medical Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
| | - Zhong Chen
- Institute of Pharmacology and Toxicology, Department of Pharmacology, NHC and CAMS Key Laboratory of Medical Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China.
| |
Collapse
|
4
|
Silverman RB. Design and Mechanism of GABA Aminotransferase Inactivators. Treatments for Epilepsies and Addictions. Chem Rev 2018; 118:4037-4070. [PMID: 29569907 DOI: 10.1021/acs.chemrev.8b00009] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
When the brain concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) diminishes below a threshold level, the excess neuronal excitation can lead to convulsions. This imbalance in neurotransmission can be corrected by inhibition of the enzyme γ-aminobutyric acid aminotransferase (GABA-AT), which catalyzes the conversion of GABA to the excitatory neurotransmitter l-glutamic acid. It also has been found that raising GABA levels can antagonize the rapid elevation and release of dopamine in the nucleus accumbens, which is responsible for the reward response in addiction. Therefore, the design of new inhibitors of GABA-AT, which increases brain GABA levels, is an important approach to new treatments for epilepsy and addiction. This review summarizes findings over the last 40 or so years of mechanism-based inactivators (unreactive compounds that require the target enzyme to catalyze their conversion to the inactivating species, which inactivate the enzyme prior to their release) of GABA-AT with emphasis on their catalytic mechanisms of inactivation, presented according to organic chemical mechanism, with minimal pharmacology, except where important for activity in epilepsy and addiction. Patents, abstracts, and conference proceedings are not covered in this review. The inactivation mechanisms described here can be applied to the inactivations of a wide variety of unrelated enzymes.
Collapse
Affiliation(s)
- Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , United States
| |
Collapse
|
5
|
Effects of anti-epileptic drugs on spreading depolarization-induced epileptiform activity in mouse hippocampal slices. Sci Rep 2017; 7:11884. [PMID: 28928441 PMCID: PMC5605655 DOI: 10.1038/s41598-017-12346-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 09/07/2017] [Indexed: 01/08/2023] Open
Abstract
Epilepsy and spreading depolarization (SD) are both episodic brain disorders and often exist together in the same individual. In CA1 pyramidal neurons of mouse hippocampal slices, induction of SD evoked epileptiform activities, including the ictal-like bursts, which occurred during the repolarizing phase of SD, and the subsequent generation of paroxysmal depolarization shifts (PDSs), which are characterized by mild depolarization plateau with overriding spikes. The duration of the ictal-like activity was correlated with both the recovery time and the depolarization potential of SD, whereas the parameters of PDSs were not significantly correlated with the parameters of SD. Moreover, we systematically evaluated the effects of multiple anti-epileptic drugs (AEDs) on SD-induced epileptiform activity. Among the drugs that are known to inhibit voltage-gated sodium channels, carbamazepine, phenytoin, valproate, lamotrigine, and zonisamide reduced the frequency of PDSs and the overriding firing bursts in 20–25 min after the induction of SD. The GABA uptake inhibitor tiagabine exhibited moderate effects and partially limited the incidence of PDSs after SD. AEDs including gabapentin, levetiracetam, ethosuximide, felbamate, and vigabatrin, had no significant effect on SD-induced epileptic activity. Taken together, these results demonstrate the effects of AEDs on SD and the related epileptiform activity at the cellular level.
Collapse
|
6
|
Sousa K, Decker N, Pires TR, Papke DKM, Coelho VR, Pflüger P, Pereira P, Picada JN. Neurobehavioral effects of vigabatrin and its ability to induce DNA damage in brain cells after acute treatment in rats. Psychopharmacology (Berl) 2017; 234:129-136. [PMID: 27678549 DOI: 10.1007/s00213-016-4446-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 09/19/2016] [Indexed: 12/29/2022]
Abstract
RATIONALE Vigabatrin (VGB) is a drug indicated mostly for the treatment of spasms in childhood and West's syndrome patients. This drug inhibits irreversibly the enzyme GABA-transaminase (GABA-T), increasing GABA concentrations and enhancing GABAergic neurotransmission in the brain, which is known to induce behavioral changes. OBJECTIVES The aims of this study were to evaluate the effects of VGB in the short-term memory (STM), long-term memory (LTM), motivation, locomotion, and exploratory behavior tests and to detect deleterious or protective effects on DNA in target tissues of the drug. METHODS Male Wistar rats were treated with a single dose of VGB (100, 250, or 500 mg/kg) or saline solution before the inhibitory avoidance and open-field tasks. DNA damage was evaluated using the alkaline comet assay in peripheral blood, cerebral cortex, and hippocampus after behavioral testing. RESULTS There was no significant difference in the inhibitory avoidance task between the treated groups and the saline group. In all tested doses, VGB reduced the number of rearings in the open-field task. Besides, VGB 500 mg/kg affected locomotion, though it was not able to induce any DNA damage. CONCLUSIONS VGB did not affect STM and LTM, but the drug impaired the exploration and locomotion likely associated with its sedative effect. In addition, no DNA damage in cortex and hippocampus was detected after behavioral testing, when brain GABA levels are already increased.
Collapse
Affiliation(s)
- Karen Sousa
- Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA), Farroupilha Avenue, 8001, Canoas, RS, 2425-900, Brazil
| | - Natalia Decker
- Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA), Farroupilha Avenue, 8001, Canoas, RS, 2425-900, Brazil
| | - Thienne Rocha Pires
- Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA), Farroupilha Avenue, 8001, Canoas, RS, 2425-900, Brazil
| | - Débora Kuck Mausolff Papke
- Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA), Farroupilha Avenue, 8001, Canoas, RS, 2425-900, Brazil
| | - Vanessa Rodrigues Coelho
- Laboratory of Neuropharmacology and Pre-Clinical Toxicology. Pharmacology Department, Institute for Basic Health Sciences, Federal University of Rio Grande do Sul (UFRGS), Sarmento Leite Street, 500/305, Porto Alegre, RS, 90050-170, Brazil
| | - Pricila Pflüger
- Laboratory of Neuropharmacology and Pre-Clinical Toxicology. Pharmacology Department, Institute for Basic Health Sciences, Federal University of Rio Grande do Sul (UFRGS), Sarmento Leite Street, 500/305, Porto Alegre, RS, 90050-170, Brazil
| | - Patrícia Pereira
- Laboratory of Neuropharmacology and Pre-Clinical Toxicology. Pharmacology Department, Institute for Basic Health Sciences, Federal University of Rio Grande do Sul (UFRGS), Sarmento Leite Street, 500/305, Porto Alegre, RS, 90050-170, Brazil
| | - Jaqueline Nascimento Picada
- Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA), Farroupilha Avenue, 8001, Canoas, RS, 2425-900, Brazil.
| |
Collapse
|
7
|
Pinto A, Tamborini L, Pennacchietti E, Coluccia A, Silvestri R, Cullia G, De Micheli C, Conti P, De Biase D. Bicyclic γ-amino acids as inhibitors of γ-aminobutyrate aminotransferase. J Enzyme Inhib Med Chem 2015; 31:295-301. [DOI: 10.3109/14756366.2015.1021251] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Andrea Pinto
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milano, Italy,
| | - Lucia Tamborini
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milano, Italy,
| | - Eugenia Pennacchietti
- Istituto Pasteur – Fondazione Cenci Bolognetti, Dipartimento di Scienze e Biotecnologie Medico-Chirurgiche, Sapienza Università di Roma, Latina, Italy, and
| | - Antonio Coluccia
- Istituto Pasteur – Fondazione Cenci Bolognetti, Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza Università di Roma, Roma, Italy
| | - Romano Silvestri
- Istituto Pasteur – Fondazione Cenci Bolognetti, Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza Università di Roma, Roma, Italy
| | - Gregorio Cullia
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milano, Italy,
| | - Carlo De Micheli
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milano, Italy,
| | - Paola Conti
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, Milano, Italy,
| | - Daniela De Biase
- Istituto Pasteur – Fondazione Cenci Bolognetti, Dipartimento di Scienze e Biotecnologie Medico-Chirurgiche, Sapienza Università di Roma, Latina, Italy, and
| |
Collapse
|
8
|
|
9
|
Durak AT, Gökcan H, Konuklar FAS. Theoretical studies on the inactivation mechanism of γ-aminobutyric acid aminotransferase. Org Biomol Chem 2011; 9:5162-71. [DOI: 10.1039/c1ob05146f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
10
|
Elterman RD, Shields WD, Bittman RM, Torri SA, Sagar SM, Collins SD. Vigabatrin for the treatment of infantile spasms: final report of a randomized trial. J Child Neurol 2010; 25:1340-7. [PMID: 20404353 DOI: 10.1177/0883073810365103] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A large randomized study was conducted in patients with newly diagnosed infantile spasms to compare 2 doses of vigabatrin in achieving spasm cessation. High (100-148 mg/kg/d) and low (18-36 mg/kg/d) oral doses of vigabatrin were evaluated in a randomized, single-blind study of 14 to 21 days with subsequent open-label treatment up to 3 years. Spasm cessation was defined as 7 consecutive days of spasm freedom beginning within the first 14 days, confirmed by video-electroencephalogram. A total of 221 subjects comprised the modified intent-to-treat cohort. More subjects in the high-dose group achieved spasm cessation compared with the low-dose vigabatrin group (15.9% [17/107] vs 7.0% [8/114]; P = .0375). During follow-up, 39 of 171 (23%) subjects relapsed; 28 of 39 (72%) regained spasm freedom. Adverse events were primarily mild to moderate in severity. Vigabatrin had a dose-dependent effect in spasm reduction. Spasm cessation occurred rapidly and was maintained in the majority of infants.
Collapse
Affiliation(s)
- Roy D Elterman
- Dallas Pediatric Neurology Associates, Medical City Dallas Hospital, Dallas, TX 75230-2507, USA.
| | | | | | | | | | | |
Collapse
|
11
|
Potashman MH, Duggan ME. Covalent Modifiers: An Orthogonal Approach to Drug Design. J Med Chem 2009; 52:1231-46. [DOI: 10.1021/jm8008597] [Citation(s) in RCA: 265] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michele H. Potashman
- Department of Medicinal Chemistry, Amgen Inc., One Kendall Square, Building 1000, Cambridge, Massachusetts 02139
| | - Mark E. Duggan
- Department of Medicinal Chemistry, Amgen Inc., One Kendall Square, Building 1000, Cambridge, Massachusetts 02139
| |
Collapse
|
12
|
Clark SM, Di Leo R, Dhanoa PK, Van Cauwenberghe OR, Mullen RT, Shelp BJ. Biochemical characterization, mitochondrial localization, expression, and potential functions for an Arabidopsis gamma-aminobutyrate transaminase that utilizes both pyruvate and glyoxylate. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:1743-57. [PMID: 19264755 PMCID: PMC2671622 DOI: 10.1093/jxb/erp044] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 01/31/2009] [Accepted: 02/04/2009] [Indexed: 05/18/2023]
Abstract
Gamma-aminobutyrate transaminase (GABA-T) catalyses the breakdown of GABA to succinic semialdehyde. In this report, the previously identified Arabidopsis thaliana (L.) Heyhn GABA-T (AtGABA-T) was characterized in more detail. Full-length AtGABA-T contains an N-terminal 36 amino acid long targeting pre-sequence (36 amino acids) that is both sufficient and necessary for targeting the enzyme to mitochondria. Removal of the pre-sequence encoding this N-terminal targeting domain and co-expression of the resulting truncated AtGABA-T cDNA with the GroES/EL molecular chaperone complex in Escherichia coli yielded good recovery of the soluble recombinant proteins. Activity assays indicated that purified recombinant GABA-T has both pyruvate- and glyoxylate-dependent activities, but cannot utilize 2-oxoglutarate as amino acceptor. Kinetic parameters for glyoxylate- and pyruvate-dependent GABA-T activities were similar, with physiologically relevant affinities. Assays of GABA-T activity in cell-free leaf extracts from wild-type Arabidopsis and two knockout mutants in different genetic backgrounds confirmed that the native enzyme possesses both pyruvate- and glyoxylate-dependent activities. The GABA-T transcript was present throughout the plant, but its expression was highest in roots and increased as a function of leaf development. A GABA-T with dual functions suggests the potential for interaction between GABA metabolism and photorespiratory glyoxylate production.
Collapse
Affiliation(s)
- Shawn M. Clark
- Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Rosa Di Leo
- Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Preetinder K. Dhanoa
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | | - Robert T. Mullen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Barry J. Shelp
- Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada N1G 2W1
- To whom correspondence should be addressed. E-mail:
| |
Collapse
|
13
|
Abstract
This review considers how recent advances in the physiology of ion channels and other potential molecular targets, in conjunction with new information on the genetics of idiopathic epilepsies, can be applied to the search for improved antiepileptic drugs (AEDs). Marketed AEDs predominantly target voltage-gated cation channels (the alpha subunits of voltage-gated Na+ channels and also T-type voltage-gated Ca2+ channels) or influence GABA-mediated inhibition. Recently, alpha2-delta voltage-gated Ca2+ channel subunits and the SV2A synaptic vesicle protein have been recognized as likely targets. Genetic studies of familial idiopathic epilepsies have identified numerous genes associated with diverse epilepsy syndromes, including genes encoding Na+ channels and GABA(A) receptors, which are known AED targets. A strategy based on genes associated with epilepsy in animal models and humans suggests other potential AED targets, including various voltage-gated Ca2+ channel subunits and auxiliary proteins, A- or M-type voltage-gated K+ channels, and ionotropic glutamate receptors. Recent progress in ion channel research brought about by molecular cloning of the channel subunit proteins and studies in epilepsy models suggest additional targets, including G-protein-coupled receptors, such as GABA(B) and metabotropic glutamate receptors; hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel subunits, responsible for hyperpolarization-activated current Ih; connexins, which make up gap junctions; and neurotransmitter transporters, particularly plasma membrane and vesicular transporters for GABA and glutamate. New information from the structural characterization of ion channels, along with better understanding of ion channel function, may allow for more selective targeting. For example, Na+ channels underlying persistent Na+ currents or GABA(A) receptor isoforms responsible for tonic (extrasynaptic) currents represent attractive targets. The growing understanding of the pathophysiology of epilepsy and the structural and functional characterization of the molecular targets provide many opportunities to create improved epilepsy therapies.
Collapse
Affiliation(s)
- Brian S Meldrum
- Centre for Neuroscience, Division of Biomedical and Health Sciences, School of Medicine, Kings College, London, United Kingdom
| | | |
Collapse
|
14
|
Tong X, Ratnaraj N, Patsalos PN. The pharmacokinetics of vigabatrin in rat blood and cerebrospinal fluid. Seizure 2007; 16:43-9. [PMID: 17118677 DOI: 10.1016/j.seizure.2006.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2004] [Revised: 10/03/2006] [Accepted: 10/23/2006] [Indexed: 11/22/2022] Open
Abstract
PURPOSE Data on the blood pharmacokinetics of vigabatrin, an antiepileptic drug with a unique and novel mechanism of action, in the rat are sparse. Additionally, little is known of the kinetics of vigabatrin in the central cerebrospinal fluid (CSF) compartment. We therefore investigated the rate of penetration into and the inter-relationship between serum and CSF compartments following systemic administration of vigabatrin in the rat. METHODS Sprague-Dawley rats were implanted with a jugular vein catheter and a cisterna magna catheter for blood and CSF sampling, respectively. Vigabatrin was administered by intraperitonial injection at three different doses (250, 500 and 1000mg/kg) and blood and CSF collected at timed intervals up to 8h. Vigabatrin concentrations in sera and CSF were determined by high performance liquid chromatography. RESULTS Vigabatrin concentrations in blood and CSF rose linearly and dose-dependently and the time to maximum concentration (Tmax) was 0.4 and 1.0h, respectively. Vigabatrin is not protein bound in serum and its elimination from serum (mean t1/2 values, 1.1-1.4 h) is rapid and dose-independent. The efflux of vigabatrin from CSF was significantly slower than that seen for serum (mean t1/2 values, 2.2-3.3h). CONCLUSIONS The kinetics of vigabatrin are linear with rapid entry into CSF. However, although vigabatrin CSF kinetics parallel that seen in serum, CSF vigabatrin concentrations represent only 2% of concentrations seen in serum and do not reflect free drug concentrations in serum.
Collapse
Affiliation(s)
- X Tong
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | | | | |
Collapse
|
15
|
Berkowitz DB, Wu B, Li H. A formal [3,3]-sigmatropic rearrangement route to quaternary alpha-vinyl amino acids: use of allylic N-PMP trifluoroacetimidates. Org Lett 2006; 8:971-4. [PMID: 16494487 PMCID: PMC2504469 DOI: 10.1021/ol060019s] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pd(II)-mediated rearrangement of allylic N-PMP (p-methoxyphenyl) trifluoroacetimidates provides the first formal sigmatropic route to quaternary, alpha-vinylic amino acids, potential suicide substrates for PLP enzymes. The amino acid side chains enter via transition-metal-mediated C-C bond constructions, including (i) Cu(I)-mediated conjugate addition (Ala); (ii) Pd(0)/AsPh3-mediated Stille coupling (allyl-Gly, Phe, DOPA, m-Tyr); and (iii) Pd(0)/Pt-Bu3-mediated Negishi coupling (Leu). In the synthesis of the DOPA decarboxylase inactivator, alpha-vinyl-m-tyrosine, the new N-PMP trifluoroacetimidate rearranges much more efficiently than the corresponding trichloroacetimidate.
Collapse
Affiliation(s)
- David B Berkowitz
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
| | | | | |
Collapse
|
16
|
Berkowitz DB, Charette BD, Karukurichi KR, McFadden JM. α-Vinylic Amino Acids: Occurrence, Asymmetric Synthesis and Biochemical Mechanisms. TETRAHEDRON, ASYMMETRY 2006; 17:869-882. [PMID: 29977107 PMCID: PMC6029878 DOI: 10.1016/j.tetasy.2006.02.026] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
This report presents an overview of the family of naturally occurring 'vinylic' amino acids, namely those that feature a C-C double bond directly attached to the α-carbon, along the side chain. Strategies that have been brought to bear on the stereocontrolled synthesis of these olefinic amino acids are surveyed. The mechanistic diversity by which such 'vinylic triggers' can be actuated in a PLP (pyridoxal phosphate) enzyme active site is then highlighted by discussions of vinylglycine (VG), its substituted congeners, particularly AVG [4E-(2'-aminoethoxy)vinylglycine], and a naturally occurring VG-progenitor, SMM (S-methylmethionine).
Collapse
Affiliation(s)
- David B Berkowitz
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304
| | | | | | - Jill M McFadden
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304
| |
Collapse
|
17
|
Choi SY, Ahn EM, Song MC, Kim DW, Kang JH, Kwon OS, Kang TC, Baek NI. In vitro GABA-transaminase inhibitory compounds from the root ofAngelica dahurica. Phytother Res 2005; 19:839-45. [PMID: 16261512 DOI: 10.1002/ptr.1424] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The 80% aqueous MeOH extracts from the root of Angelica dahurica, found to inhibit the activities of GABA degradative enzymes GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH), were fractionated using EtOAc, n-BuOH and H2O. Repeated column chromatography for the EtOAc and n-BuOH fractions led to the isolation of two new coumarins, oxypeucedanin hydrate-3''-butyl ether and isopraeroside IV along with six known coumarins, isoimperatorin, imperatorin, phellopterin, oxypeucedanin hydrate, nodakenin and 3'-hydroxymarmesinin, and two polyacetylenes, falcarindiol and octadeca-1,9-dien-4,6-diyn-3,8,18-triol. Of the isolated pure compounds, imperatorin and falcarindiol inactivated the GABA-T activities in both time- and concentration-dependent manners. The kinetic studies showed that imperatorin and falcarindiol reacted with the GABA-T with a second-order rate constant of 2.3 +/- 0.2 mm(-1) min(-1) and 1.5 +/- 0.1 mm(-1) min(-1), respectively. It is postulated that imperatorin and falcarindiol are able to elevate the neurotransmitter GABA levels in the central nervous system by an inhibitory action on the GABA degradative enzyme GABA-T.
Collapse
Affiliation(s)
- Soo Young Choi
- Department of Biomedical Sciences, Division of Life Sciences, Hallym University, Chuncheon 200-702, Korea
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Storici P, Qiu J, Schirmer T, Silverman RB. Mechanistic Crystallography. Mechanism of Inactivation of γ-Aminobutyric Acid Aminotransferase by (1R,3S,4S)-3-Amino-4-fluorocyclopentane-1-carboxylic Acid As Elucidated by Crystallography†. Biochemistry 2004; 43:14057-63. [PMID: 15518554 DOI: 10.1021/bi0487185] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
(1R,3S,4S)-3-Amino-4-fluorocyclopentane-1-carboxylic acid (7) was previously shown to be a mechanism-based inactivator of gamma-aminobutyric acid aminotransferase (GABA-AT) [Qiu, J. and Silverman, R. B. (2000) J. Med. Chem. 43, 706-720]. Two mechanisms were considered as reasonable possibilities, a Michael addition mechanism and an enamine mechanism. On the basis of a variety of chemical studies, including tedious radiolabeling experiments, it was concluded that inactivation by 7 proceeds by a Michael addition mechanism. Here, a crystal structure of 7 bound to pig liver GABA-AT is reported, which clearly demonstrates that the adduct formed is derived from an enamine mechanism. This represents another example of how crystallography is an important tool for elucidation of inactivation mechanisms.
Collapse
Affiliation(s)
- Paola Storici
- Division of Structural Biology, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
| | | | | | | |
Collapse
|
19
|
Affiliation(s)
- Michael A Rogawski
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | |
Collapse
|
20
|
Storici P, De Biase D, Bossa F, Bruno S, Mozzarelli A, Peneff C, Silverman RB, Schirmer T. Structures of γ-Aminobutyric Acid (GABA) Aminotransferase, a Pyridoxal 5′-Phosphate, and [2Fe-2S] Cluster-containing Enzyme, Complexed with γ-Ethynyl-GABA and with the Antiepilepsy Drug Vigabatrin. J Biol Chem 2004; 279:363-73. [PMID: 14534310 DOI: 10.1074/jbc.m305884200] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gamma-aminobutyric acid aminotransferase (GABA-AT) is a pyridoxal 5'-phosphate-dependent enzyme responsible for the degradation of the inhibitory neurotransmitter GABA. GABA-AT is a validated target for antiepilepsy drugs because its selective inhibition raises GABA concentrations in brain. The antiepilepsy drug, gamma-vinyl-GABA (vigabatrin) has been investigated in the past by various biochemical methods and resulted in several proposals for its mechanisms of inactivation. In this study we solved and compared the crystal structures of pig liver GABA-AT in its native form (to 2.3-A resolution) and in complex with vigabatrin as well as with the close analogue gamma-ethynyl-GABA (to 2.3 and 2.8 A, respectively). Both inactivators form a covalent ternary adduct with the active site Lys-329 and the pyridoxal 5'-phosphate (PLP) cofactor. The crystal structures provide direct support for specific inactivation mechanisms proposed earlier on the basis of radio-labeling experiments. The reactivity of GABA-AT crystals with the two GABA analogues was also investigated by polarized absorption microspectrophotometry. The spectral data are discussed in relation to the proposed mechanism. Intriguingly, all three structures revealed a [2Fe-2S] cluster of yet unknown function at the center of the dimeric molecule in the vicinity of the PLP cofactors.
Collapse
Affiliation(s)
- Paola Storici
- Division of Structural Biology, Biozentrum, University of Basel, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Choi S, Silverman RB. Inactivation and inhibition of gamma-aminobutyric acid aminotransferase by conformationally restricted vigabatrin analogues. J Med Chem 2002; 45:4531-9. [PMID: 12238932 DOI: 10.1021/jm020134i] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Four cyclohexene analogues of gamma-aminobutyric acid (GABA) and beta-alanine were designed as conformationally rigid analogues of the epilepsy and drug addiction drug vigabatrin and as potential mechanism-based inactivators of gamma-aminobutyric acid aminotransferase (GABA-AT). The corresponding cyclopentene analogues were previously reported to be inhibitors, but not inactivators, of GABA-AT (Qiu, J.; Pingsterhaus, J.; Silverman, R. B. J. Med. Chem. 1999, 42, 4725-4728). cis-3-Aminocyclohex-4-ene-1-carboxylic acid (3) and cis-2-aminocyclohex-3-ene-1-carboxylic acid (5) showed time- and concentration-dependent, irreversible inactivation of GABA-AT. In both cases, the inactivations are protected by substrate, indicating that they are active site-directed. trans-3-Aminocyclohex-4-ene-1-carboxylic acid (4) and trans-2-aminocyclohex-3-ene-1-carboxylic acid (6) are not inactivators but are competitive reversible inhibitors of GABA-AT. Unlike the cyclopentene analogues, there appears to be sufficient ring flexibility to allow inactivation to occur. The orientation of the carboxylic and amino groups of these analogues is important for their binding to GABA-AT. Molecular modeling of GABA-AT with 3-6 and molecular dynamics simulations with vigabatrin bound provide rationalizations for the inhibitory properties of these compounds.
Collapse
Affiliation(s)
- Sun Choi
- Department of Chemistry and the Drug Discover Program, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | |
Collapse
|
22
|
Choi S, Storici P, Schirmer T, Silverman RB. Design of a conformationally restricted analogue of the antiepilepsy drug Vigabatrin that directs its mechanism of inactivation of gamma-aminobutyric acid aminotransferase. J Am Chem Soc 2002; 124:1620-4. [PMID: 11853435 DOI: 10.1021/ja011968d] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The antiepilepsy drug vigabatrin (1, 4-aminohex-5-enoic acid, gamma-vinylGABA) is known to be a mechanism-based inactivator of the pyridoxal phosphate (PLP)-dependent enzyme gamma-aminobutyric acid aminotransferase (GABA-AT). Inactivation has been shown to proceed by two divergent mechanisms (Nanavati, S. M.; Silverman, R. B. J. Am. Chem. Soc. 1991, 113, 9341-9349). The major pathway involves gamma-proton removal, tautomerization into the PLP ring, followed by Michael addition of an active site lysine residue at the conjugated vinyl group to give a stable covalent adduct with the protein (Scheme 2, pathway a). The minor inactivation mechanism also involves gamma-proton removal, but tautomerization occurs through the vinyl group, followed by an enamine rearrangement that leads to attachment of the inactivator to the PLP, which is bound to the protein (Scheme 2, pathway b). The cause for the two different inactivation pathways was hypothesized to be potential overlap of the incipient carbanion with the pi-orbitals of both the PLP and the vinyl group. With use of the crystal structure data for GABA-AT recently reported (Storici, P.; Capitani, C.; De Biase, D.; Moser, M.; John, R. A.; Jansonius, J. N.; Schirmer, T. Biochemistry 1999, 38, 8628-8634) a computer model of vigabatrin bound to the PLP was constructed and energy minimized. This model indicated that the major Michael addition pathway could only occur if the vinyl group were allowed to rotate by 180 degrees. A conformationally rigid analogue of vigabatrin, cis-3-aminocyclohex-4-ene-1-carboxylic acid (9), was designed to prevent bond rotation and block the Michael addition pathway. A detailed study of the mechanism of inactivation of GABA-AT by 9 revealed that it inactivates by a single mechanism, the enamine pathway.
Collapse
Affiliation(s)
- Sun Choi
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | | | | | |
Collapse
|
23
|
Jeon SG, Bahn JH, Jang JS, Park J, Kwon OS, Cho SW, Choi SY. Human brain GABA transaminase tissue distribution and molecular expression. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:5601-7. [PMID: 10951220 DOI: 10.1046/j.1432-1327.2000.01626.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Human brain gamma-aminobutyrate transaminase is differentially expressed in a tissue-specific manner. mRNA master dot-blot analysis for 50 different human tissues, including different brain regions and fetal tissues, provided a complete map of the tissue distribution. Genomic Southern analysis revealed that the gamma-aminobutyrate transaminase gene is a single copy, at least 15 kb in size. In addition, human brain gamma-aminobutyrate transaminase cDNA was expressed in Escherichia coli using a pGEX expression vector system. Catalytically active gamma-aminobutyrate transaminase was expressed in large quantities and the purified recombinant enzyme had kinetic parameters that were indistinguishable from those isolated from other mammalian brains. The human enzyme was inactivated by a well-known antiepileptic drug vigabatrin. Values of Ki and kinact were 1 mM and 0.35 min-1, respectively. Results from inactivation kinetics suggested that human gamma-aminobutyrate transaminase is more sensitive to the vigabatrin drug than the enzyme isolated from bovine brain.
Collapse
Affiliation(s)
- S G Jeon
- Department of Genetic Engineering, Hallym University, Chunchon, Korea
| | | | | | | | | | | | | |
Collapse
|
24
|
Baek NI, Jeon SG, Ahn EM, Hahn JT, Bahn JH, Jang JS, Cho SW, Park JK, Choi SY. Anticonvulsant compounds from the wood of Caesalpinia sappan L. Arch Pharm Res 2000; 23:344-8. [PMID: 10976581 DOI: 10.1007/bf02975445] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
80% Aqueous MeOH extracts from the wood of Caesalpinia sappan, which showed remarkable anticonvulsant activity, were fractionated using EtOAc, n-BuOH, and H2O. Among them, the EtOAc fraction significantly inhibited the activities of two GABA degradative enzymes, succinic semialdehyde dehydrogenase (SSADH) and succinic semialdehyde reductase (SSAR). Repeated column chromatographies for the fraction guided by activity test led to the isolation of the two active principal components. Their chemical structures were determined to be sappanchalcone and brazilin based on spectral data. The pure compounds, sappanchalcone (1) and brazilin (2), inactivated the SSAR activities in a dose dependent manner, whereas SSADH was inhibited partially by sappanchalcone and not by brazilin.
Collapse
Affiliation(s)
- N I Baek
- Department of Life Sciences, Kyunghee University, Suwon, Korea.
| | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Sills GJ, Butler E, Thompson GG, Brodie MJ. Vigabatrin and tiagabine are pharmacologically different drugs. A pre-clinical study. Seizure 1999; 8:404-11. [PMID: 10600581 DOI: 10.1053/seiz.1999.0326] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In light of theirclosely related mechanisms of action, and preliminary clinical evidence suggesting that they possess similar efficacies, it has been anecdotally suggested that vigabatrin and tiagabine may prove to be therapeutically indistinguishable. As a result, we have conducted a preclinical comparison of their anticonvulsant profile and mechanism of action. Pentylenetetrazol and maximal electroshock seizures were employed to determine the experimental anticonvulsant profile. Mechanisms of action were investigated using assays of gamma -aminobutyric acid (GABA), GABA-transaminase and glutamic acid decarboxylase in mouse brain and GABA uptake and GABA-transaminase in rat astrocyte cultures. Vigabatrin was without effect on either pentylenetetrazol- or maximal electroshock-induced seizures, whereas tiagabine increased the latency to pentylenetetrazol seizures and reduced the incidence of maximal electroshock seizures. In mouse brain assays, tiagabine was without effect, while vigabatrin increased GABA concentrations and reduced GABA-transaminase and glutamic acid decarboxylase activities. In cortical astrocyte cultures, vigabatrin reduced the activities of both GABA uptake and GABA-transaminase, whereas tiagabine blocked GABA uptake alone. These results suggest that vigabatrin and tiagabine have differing efficacy in experimental seizure models and distinct neurochemical effects. It is possible, then, that these drugs will have different spectra of activity and toxicity profiles in human epilepsy.
Collapse
Affiliation(s)
- G J Sills
- Epilepsy Unit, University Department of Medicine and Therapeutics, Western Infirmary, Glasgow, Scotland, UK.
| | | | | | | |
Collapse
|
26
|
Fu M, Silverman RB. Isolation and characterization of the product of inactivation of gamma-aminobutyric acid aminotransferase by gabaculine. Bioorg Med Chem 1999; 7:1581-90. [PMID: 10482450 DOI: 10.1016/s0968-0896(99)00081-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Gabaculine (5-amino-1,3-cyclohexadienylcarboxylic acid, 1), a naturally occurring neurotoxin isolated from Streptomyces toyocaenis, has been shown to be a mechanism-based inactivator of gamma-aminobutyric acid aminotransferase (GABA-AT) (Rando, R. R. Biochemistry 1977, 16, 4604). Inactivation results from reaction of gabaculine with the pyridoxal 5'-phosphate (PLP) cofactor. Two HPLC systems for isolating this inactivator-PLP adduct are described as well as a detailed characterization of the adduct, including the ultraviolet-visible spectrum, electrospray mass spectra, and NMR spectrum. The same spectral characterization of the chemically synthesized gabaculine-PLP adduct is also reported.
Collapse
Affiliation(s)
- M Fu
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
| | | |
Collapse
|
27
|
Storici P, Capitani G, De Biase D, Moser M, John RA, Jansonius JN, Schirmer T. Crystal structure of GABA-aminotransferase, a target for antiepileptic drug therapy. Biochemistry 1999; 38:8628-34. [PMID: 10393538 DOI: 10.1021/bi990478j] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
gamma-Aminobutyrate aminotransferase (GABA-AT), a pyridoxal phosphate-dependent enzyme, is responsible for the degradation of the inhibitory neurotransmitter GABA and is a target for antiepileptic drugs because its selective inhibition raises GABA concentrations in brain. The X-ray structure of pig GABA-AT has been determined to 3.0 A resolution by molecular replacement with the distantly related enzyme ornithine aminotransferase. Both omega-aminotransferases have the same fold, but exhibit side chain replacements in the closely packed binding site that explain their respective specificities. The aldimines of GABA and the antiepileptic drug vinyl-GABA have been modeled into the active site.
Collapse
Affiliation(s)
- P Storici
- Division of Structural Biology, Biozentrum, University of Basel, Switzerland.
| | | | | | | | | | | | | |
Collapse
|
28
|
Qiu J, Stevenson SH, O'Beirne MJ, Silverman RB. 2,6-Difluorophenol as a bioisostere of a carboxylic acid: bioisosteric analogues of gamma-aminobutyric acid. J Med Chem 1999; 42:329-32. [PMID: 9925739 DOI: 10.1021/jm980435l] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
3-(Aminomethyl)-2,6-difluorophenol (6) and 4-(aminomethyl)-2, 6-difluorophenol (7) were synthesized in eight and four steps, respectively, starting from 2,6-difluorophenol, to test the potential of the 2,6-difluorophenol moiety to act as a lipophilic bioisostere of a carboxylic acid. Compounds 6 and 7 are potential bioisosteric analogues of gamma-aminobutyric acid (GABA). Substrate studies and inhibition studies were carried out with pig brain gamma-aminobutyric acid aminotransferase; 6 and 7 are very poor substrates, but both inhibit the enzyme, indicating that the 2, 6-difluorophenol moiety appears to be able to substitute for a carboxylic acid to increase the lipophilicity of drug candidates.
Collapse
Affiliation(s)
- J Qiu
- Departments of Chemistry and of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | | | | | |
Collapse
|
29
|
Tramonti A, De Biase D, Giartosio A, Bossa F, John RA. The roles of His-167 and His-275 in the reaction catalyzed by glutamate decarboxylase from Escherichia coli. J Biol Chem 1998; 273:1939-45. [PMID: 9442028 DOI: 10.1074/jbc.273.4.1939] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Two histidine residues in glutamate decarboxylase from Escherichia coli, potential participants in catalysis because they are conserved among amino acid decarboxylases and because they are at the active site in the homologous enzyme ornithine decarboxylase, were mutated. His-275 is shown to bind the cofactor pyridoxal 5'-phosphate but not to contribute directly to catalysis. The H275N enzyme was unable to bind the cofactor whereas the H275Q mutant contained 50% of the normal complement of cofactor and its specific activity (expressed per mole of cofactor) was 70% of that of the wild-type enzyme. The H167N mutant bound the cofactor tightly, its specific activity was approximately half that of the wild-type enzyme and experiments in D2O showed that it catalyzed replacement of the carboxyl group with retention of configuration as does the wild-type enzyme. Comparison of reaction profiles by observing changes in the absorbance of the cofactor after stopped-flow mixing, revealed that a slow reaction, in which approximately one-third of the wild-type enzyme is converted to an unreactive complex during catalysis, does not occur with the H167N mutant enzyme. This reaction is attributed to a substrate-induced conformational change, a proposal that is supported by differential scanning calorimetry.
Collapse
Affiliation(s)
- A Tramonti
- Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università La Sapienza, Roma, Italy
| | | | | | | | | |
Collapse
|
30
|
Amoresano A, Siciliano R, Orrù S, Napoleoni R, Altarocca V, De Luca E, Sirna A, Pucci P. Structural characterisation of human recombinant glycohormones follitropin, lutropin and choriogonadotropin expressed in Chinese hamster ovary cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 242:608-18. [PMID: 9022688 DOI: 10.1111/j.1432-1033.1996.0608r.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The alpha and beta chains from human recombinant gonadotropins follitropin, lutropin and choriogonadotropin expressed in CHO cells have been structurally characterised both at the protein and at the carbohydrate level by using advanced mass spectrometric procedures. The three alpha chains share the same amino acid sequence while they display different glycosylation patterns. The oligosaccharide structures detected belong to the complex-type glycans with different degree of sialylation. Partial proteolytic processing occurred at the N-terminus of the follitropin beta chain and at the C-terminus of the lutropin beta chain. The N-linked glycans from the three beta chains were found to contain fucosylated and sialylated diantennary and triantennary complex-type structures. The follitropin beta chain showed the presence of N-acetyllactosamine repeats on the antennae. The overall structure of the recombinant glycohormones corresponds to their natural counterparts with the exception that sulphated terminal glycosylation is missing.
Collapse
Affiliation(s)
- A Amoresano
- Servizio di Spettrometria di Massa del CNR, Naples, Italy
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Toney MD, Pascarella S, De Biase D. Active site model for gamma-aminobutyrate aminotransferase explains substrate specificity and inhibitor reactivities. Protein Sci 1995; 4:2366-74. [PMID: 8563634 PMCID: PMC2143008 DOI: 10.1002/pro.5560041115] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A homology model for the pig isozyme of the pyridoxal phosphate-dependent enzyme gamma-aminobutyrate (GABA) aminotransferase has been built based mainly on the structure of dialkylglycine decarboxylase and on a multiple sequence alignment of 28 evolutionarily related enzymes. The proposed active site structure is presented and analyzed. Hypothetical structures for external aldimine intermediates explain several characteristics of the enzyme. In the GABA external aldimine model, the pro-S proton at C4 of GABA, which abstracted in the 1,3-azaallylic rearrangement interconverting the aldimine and ketimine intermediates, is oriented perpendicular to the plane of the pyridoxal phosphate ring. Lys 329 is in close proximity and is probably the general base catalyst for the proton transfer reaction. The carboxylate group of GABA interacts with Arg 192 and Lys 203, which determine the specificity of the enzyme for monocarboxylic omega-amino acids such as GABA. In the proposed structure for the L-glutamate external aldimine, the alpha-carboxylate interacts with Arg 445. Glu 265 is proposed to interact with this same arginine in the GABA external aldimine, enabling the enzyme to act on omega-amino acids in one half-reaction and on alpha-amino acids in the other. The reactivities of inhibitors are well explained by the proposed active site structure. The R and S isomers of beta-substituted phenyl and p-chlorophenyl GABA would bind in very different modes due to differential steric interactions, with the reactive S isomer leaving the orientation of the GABA moiety relatively unperturbed compared to that of the natural substrate. In our model, only the reactive S isomer of the mechanism-based inhibitor vinyl-GABA, an effective anti-epileptic drug known clinically as Vigabatrin, would orient the scissile C4-H bond perpendicular to the coenzyme ring plane and present the proton to Lys 329, the proposed general base catalyst of the reaction. The R isomer would direct the vinyl group toward Lys 329 and the C4-H bond toward Arg 445. The active site model presented provides a basis for site-directed mutagenesis and drug design experiments.
Collapse
Affiliation(s)
- M D Toney
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461-1602, USA.
| | | | | |
Collapse
|
32
|
Affiliation(s)
- R A John
- School of Molecular and Medical Biosciences, University of Wales College of Cardiff, UK
| |
Collapse
|
33
|
Abstract
Over the last two decades, there have been several studies suggesting the major inhibitory amino acid neurotransmitter gamma-aminobutyric acid (GABA) is involved directly and/or indirectly in the pathogenesis of many neurologic diseases and psychiatric disorders. GABA is mainly degradated to succinic semialdehyde in a reaction catalyzed by the enzyme GABA-transaminase (GABA-T). Inhibition of this enzyme produces considerable elevation of GABA contents in the brain, and such elevation has been found to correlate with pharmacologic and behavioral effects. We focus attention, from the basic aspects, on brain and platelet GABA-T activities in various species, with a special reference to neuropsychiatric disorders. It seems that the activity of GABA-T in the brain and/or in the blood platelets is correlated to certain neuropsychiatric disorders such as alcoholism, epilepsy, and Alzheimer's disease. In animal and human studies, platelet GABA-T was identified with similar kinetic and inhibitor characteristics to those of the brain. Therefore, in this way, studies of the activity of the enzyme GABA-T in relation to neuropsychiatric disorders could be undertaken to understand, diagnose, and treat GABA-related disorders of the central nervous system.
Collapse
Affiliation(s)
- F M Sherif
- Department of Pharmacology, Faculty of Pharmacy, University of Al-Fateh for Medical Sciences, Tripoli, Libya
| | | |
Collapse
|
34
|
De Biase D, Barra D, Simmaco M, John RA, Bossa F. Primary structure and tissue distribution of human 4-aminobutyrate aminotransferase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 227:476-80. [PMID: 7851425 DOI: 10.1111/j.1432-1033.1995.tb20412.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
cDNA encoding human 4-aminobutyrate aminotransferase (aminobutyrate:2-oxoglutarate aminotransferase) was prepared by polymerase chain reaction using mRNA from human neuroblastoma cells as the template and oligonucleotides synthesized on the basis of the information obtained from direct protein sequencing. The cDNA-deduced sequence enabled peptides, sequenced by automated Edman degradation, to be aligned for confirmation of the complete primary structure. The results are compared with the recently published sequence of the rat enzyme deduced entirely from DNA sequencing [Medina-Kauwe, L. K., Tillakaratne, N. J. K., Wu, J.-Y. & Tobin, A. J. (1994) J. Neurochem. 62, 1267-1275]. Although the sequences are almost identical for most of their length, they differ in a segment of 36 residues. Almost complete identity of the two sequences is established if it is assumed that a frame-shift error was introduced into the reported rat cDNA sequence. The human cDNA was used to probe for the presence of 4-aminobutyrate aminotransferase mRNA in human tissues and a significant transcript was found in heart, placenta and in tissues usually associated with the expression of this enzyme.
Collapse
Affiliation(s)
- D De Biase
- Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università La Sapienza, Italy
| | | | | | | | | |
Collapse
|
35
|
Sherif FM. GABA-transaminase in brain and blood platelets: basic and clinical aspects. Prog Neuropsychopharmacol Biol Psychiatry 1994; 18:1219-33. [PMID: 7863013 DOI: 10.1016/0278-5846(94)90089-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Several lines of evidence suggest that the major inhibitory neuro-transmitter, gamma-aminobutyric acid (GABA) is involved, both directly and indirectly, in the pathogenesis of certain neurological and psychiatric disorders. The main enzyme responsible for GABA catabolism is gamma-aminobutyrate aminotransferase (GABA-T). Inhibition of this enzyme produces a considerable elevation of brain GABA concentrations, and such elevation has been correlated with many pharmacological effects. There seems to be that, as is discussed below, GABA-T activity in the brain and/or blood platelets is related to some neuro-psychiatric disorders such as alcoholism, epilepsy and Alzheimer's disease. GABA-T has been identified in the blood platelets with similar characteristics to those of brain GABA-T. In this way, studies on GABA-T activity in neuro-psychiatric disorders could be performed to understand, diagnosis and treat GABA-related disorders of the central nervous system (CNS).
Collapse
Affiliation(s)
- F M Sherif
- Department of Pharmacology, University for Medical Sciences, Tripoli, Libya
| |
Collapse
|
36
|
De Biase D, Maras B, Bossa F, Barra D, John RA. Protein structure of pig liver 4-aminobutyrate aminotransferase and comparison with a cDNA-deduced sequence. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 208:351-7. [PMID: 1521531 DOI: 10.1111/j.1432-1033.1992.tb17193.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The amino acid sequence of pig liver 4-aminobutyrate aminotransferase has been determined by gas-phase sequencing of proteolytically derived peptide fragments. The sequence differs substantially from that predicted for the same enzyme on the basis of the sequence of cDNA derived from pig brain in recently published work [Kwon, O., Park, J. & Churchich, J. E. (1992) J. Biol. Chem. 267, 7215-7216]. Apart from a few minor differences, the two sequences are completely different in the segment of protein comprising the 36 residues at positions 107-142. Insertion of a cytosine between bases 402 and 403 in the cDNA sequence, together with deletion of the guanine at position 510, results in a DNA sequence which predicts exactly the amino acid sequence determined by peptide analysis in the present work. The mammalian enzyme has approximately 44% sequence identity with the same enzyme from two unicellular eukaryotes (Saccharomyces cerevisiae, Aspergillus nidulans) and 22% identity with that from Escherichia coli.
Collapse
Affiliation(s)
- D De Biase
- Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università La Sapienza, Roma, Italy
| | | | | | | | | |
Collapse
|