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Silverman RB. Design and Mechanism of GABA Aminotransferase Inactivators. Treatments for Epilepsies and Addictions. Chem Rev 2018; 118:4037-4070. [PMID: 29569907 PMCID: PMC8459698 DOI: 10.1021/acs.chemrev.8b00009] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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.
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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, Evanston, Illinois, 60208-3113, United States
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Le HV, Hawker DD, Wu R, Doud E, Widom J, Sanishvili R, Liu D, Kelleher NL, Silverman RB. Design and mechanism of tetrahydrothiophene-based γ-aminobutyric acid aminotransferase inactivators. J Am Chem Soc 2015; 137:4525-33. [PMID: 25781189 PMCID: PMC4390550 DOI: 10.1021/jacs.5b01155] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Low levels of γ-aminobutyric acid (GABA), one of two major neurotransmitters that regulate brain neuronal activity, are associated with many neurological disorders, such as epilepsy, Parkinson's disease, Alzheimer's disease, Huntington's disease, and cocaine addiction. One of the main methods to raise the GABA level in human brain is to use small molecules that cross the blood-brain barrier and inhibit the activity of γ-aminobutyric acid aminotransferase (GABA-AT), the enzyme that degrades GABA. We have designed a series of conformationally restricted tetrahydrothiophene-based GABA analogues with a properly positioned leaving group that could facilitate a ring-opening mechanism, leading to inactivation of GABA-AT. One compound in the series is 8 times more efficient an inactivator of GABA-AT than vigabatrin, the only FDA-approved inactivator of GABA-AT. Our mechanistic studies show that the compound inactivates GABA-AT by a new mechanism. The metabolite resulting from inactivation does not covalently bind to amino acid residues of GABA-AT but stays in the active site via H-bonding interactions with Arg-192, a π-π interaction with Phe-189, and a weak nonbonded S···O═C interaction with Glu-270, thereby inactivating the enzyme.
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Affiliation(s)
- Hoang V. Le
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, and the Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208
| | - Dustin D. Hawker
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, and the Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208
| | - Rui Wu
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL 60660
| | - Emma Doud
- Departments of Chemistry and Molecular Biosciences, and the Proteomics Center of Excellence, Northwestern University, Evanston, IL 60208
| | - Julia Widom
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, and the Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208
| | - Ruslan Sanishvili
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439
| | - Dali Liu
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL 60660
| | - Neil L. Kelleher
- Departments of Chemistry and Molecular Biosciences, and the Proteomics Center of Excellence, Northwestern University, Evanston, IL 60208
| | - Richard B. Silverman
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, and the Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208
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Shi C, Aldrich CC. Design and synthesis of potential mechanism-based inhibitors of the aminotransferase BioA involved in biotin biosynthesis. J Org Chem 2012; 77:6051-8. [PMID: 22724679 DOI: 10.1021/jo3008435] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BioA, a pyridoxal 5'-phosphate (PLP) dependent aminotransferase, catalyzes the second step of biotin biosynthesis, converting 7-keto-8-aminopelargonic acid (KAPA) into 7,8-diaminopelargonic acid (DAPA). Amiclenomycin (ACM) isolated from cultures of different Streptomyces strains is a potent mechanism-based inhibitor of BioA that operates via an aromatization mechanism, irreversibly labeling the PLP cofactor. However, ACM is plagued by inherent chemical stability. Herein we describe the synthesis of four inhibitors, inspired by ACM but containing an allylic amine as the chemical warhead, designed to both improve stability and operate via a complementary Michael addition-pathway upon enzymatic oxidation of the allylic amine substrate to an enimine. Acyclic analogue M-1 contains a terminal olefin as the pro-Michael acceptor. The synthesis of M-1 features an alkyne-zipper reaction and the Overman rearrangement as key synthetic operations. The cyclic analogues M-2/3/4 contain either an endocyclic or exocyclic olefin as the pro-Michael acceptor. These were all prepared using a common strategy employing DIBAL reduction of a precursor bicyclic lactam, followed by in situ Horner-Wadsworth-Emmons (HWE) olefination as the key synthetic steps.
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Affiliation(s)
- Ce Shi
- Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Gökcan H, Konuklar FAS. Theoretical study on HF elimination and aromatization mechanisms: a case of pyridoxal 5' phosphate-dependent enzyme. J Org Chem 2012; 77:5533-43. [PMID: 22646918 DOI: 10.1021/jo3005815] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pyridoxal 5-phosphate (PLP), the phosphorylated and the oxidized form of vitamin B6 is an organic cofactor. PLP forms a Schiff base with the ϵ-amino group of a lysine residue of PLP-dependent enzymes. γ-Aminobutyric acid (GABA) aminotransferase is a PLP-dependent enzyme that degrades GABA to succinic semialdehyde, while reduction of GABA concentration in the brain causes convolution besides several neurological diseases. The fluorine-containing substrate analogues for the inactivation of the GABA-AT are synthesized extensively in cases where the inactivation mechanisms involve HF elimination. Although two proposed mechanisms are present for the HF elimination, the details of the base-induced HF elimination are not well identified. In this density functional theory (DFT) study, fluorine-containing substrate analogue, 5-amino-2-fluorocyclohex-3-enecarboxylic acid, is particularly chosen in order to explain the details of the HF elimination reactions. On the other hand, the experimental studies revealed that aromatization competes with Michael addition mechanism in the presence of 5-amino-2-fluorocyclohex-3-enecarboxylic acid. The results allowed us to draw a conclusion for the nature of HF elimination, besides the elucidation of the mechanism preference for the inactivation mechanism. Furthermore, the solvent phase calculations carried out in this study ensure that the proton transfer steps should be assisted either by a water molecule or a base for lower activation energy barriers.
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Affiliation(s)
- Hatice Gökcan
- Informatics Institute, Computational Science and Engineering Programme, Istanbul Technical University, Ayazağa Campus 34469, Maslak, Istanbul, Turkey
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Shi C, Geders TW, Park SW, Wilson DJ, Boshoff HI, Orisadipe A, Barry CE, Schnappinger D, Finzel BC, Aldrich CC. Mechanism-based inactivation by aromatization of the transaminase BioA involved in biotin biosynthesis in Mycobaterium tuberculosis. J Am Chem Soc 2011; 133:18194-201. [PMID: 21988601 PMCID: PMC3222238 DOI: 10.1021/ja204036t] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BioA catalyzes the second step of biotin biosynthesis, and this enzyme represents a potential target to develop new antitubercular agents. Herein we report the design, synthesis, and biochemical characterization of a mechanism-based inhibitor (1) featuring a 3,6-dihydropyrid-2-one heterocycle that covalently modifies the pyridoxal 5'-phosphate (PLP) cofactor of BioA through aromatization. The structure of the PLP adduct was confirmed by MS/MS and X-ray crystallography at 1.94 Å resolution. Inactivation of BioA by 1 was time- and concentration-dependent and protected by substrate. We used a conditional knock-down mutant of M. tuberculosis to demonstrate the antitubercular activity of 1 correlated with BioA expression, and these results provide support for the designed mechanism of action.
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Affiliation(s)
- Ce Shi
- Center for Drug Design, Academic Health Center, University of Minnesota, MN, 55455, United States
| | - Todd W. Geders
- Department of Medicinal Chemistry, University of Minnesota, MN, 55455, United States
| | - Sae Woong Park
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, 10065, United States
| | - Daniel J. Wilson
- Center for Drug Design, Academic Health Center, University of Minnesota, MN, 55455, United States
| | - Helena I. Boshoff
- Tuberculosis Research Section, National Institute of Allergy and Infectious Diseases, Bethesda, MD, 20892, United States
| | - Abayomi Orisadipe
- Tuberculosis Research Section, National Institute of Allergy and Infectious Diseases, Bethesda, MD, 20892, United States
| | - Clifton E. Barry
- Tuberculosis Research Section, National Institute of Allergy and Infectious Diseases, Bethesda, MD, 20892, United States
| | - Dirk Schnappinger
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, 10065, United States
| | - Barry C. Finzel
- Department of Medicinal Chemistry, University of Minnesota, MN, 55455, United States
| | - Courtney C. Aldrich
- Center for Drug Design, Academic Health Center, University of Minnesota, MN, 55455, United States
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Liu D, Pozharski E, Fu M, Silverman RB, Ringe D. Mechanism of inactivation of Escherichia coli aspartate aminotransferase by (S)-4-amino-4,5-dihydro-2-furancarboxylic acid . Biochemistry 2010; 49:10507-15. [PMID: 21033689 PMCID: PMC3013228 DOI: 10.1021/bi101325z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As a potential drug to treat neurological diseases, the mechanism-based inhibitor (S)-4-amino-4,5-dihydro-2-furancarboxylic acid (S-ADFA) has been found to inhibit the γ-aminobutyric acid aminotransferase (GABA-AT) reaction. To circumvent the difficulties in structural studies of a S-ADFA-enzyme complex using GABA-AT, l-aspartate aminotransferase (l-AspAT) from Escherichia coli was used as a model PLP-dependent enzyme. Crystal structures of the E. coli aspartate aminotransferase with S-ADFA bound to the active site were obtained via cocrystallization at pH 7.5 and 8. The complex structures suggest that S-ADFA inhibits the transamination reaction by forming adducts with the catalytic lysine 246 via a covalent bond while producing 1 equiv of pyridoxamine 5'-phosphate (PMP). Based on the structures, formation of the K246-S-ADFA adducts requires a specific initial binding configuration of S-ADFA in the l-AspAT active site, as well as deprotonation of the ε-amino group of lysine 246 after the formation of the quinonoid and/or ketimine intermediate in the overall inactivation reaction.
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Affiliation(s)
- Dali Liu
- Departments of Biochemistry and Chemistry, and Rosenstiel Basic Sciences Research Center MS029, Brandeis University, Waltham, Massachusetts 02454-9110
| | - Edwin Pozharski
- Departments of Biochemistry and Chemistry, and Rosenstiel Basic Sciences Research Center MS029, Brandeis University, Waltham, Massachusetts 02454-9110
| | - Mengmeng Fu
- Department of Chemistry, Department of Biochemistry, Molecular Biology, and Cell Biology, the Center for Molecular Innovation and Drug Discovery and Chemistry of Life Processes Institute, Northwestern University, and Evanston, Illinois 60208-3113
| | - Richard B. Silverman
- Department of Chemistry, Department of Biochemistry, Molecular Biology, and Cell Biology, the Center for Molecular Innovation and Drug Discovery and Chemistry of Life Processes Institute, Northwestern University, and Evanston, Illinois 60208-3113
| | - Dagmar Ringe
- Departments of Biochemistry and Chemistry, and Rosenstiel Basic Sciences Research Center MS029, Brandeis University, Waltham, Massachusetts 02454-9110
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Lepore BW, Liu D, Peng Y, Fu M, Yasuda C, Manning JM, Silverman RB, Ringe D. Chiral discrimination among aminotransferases: inactivation by 4-amino-4,5-dihydrothiophenecarboxylic acid. Biochemistry 2010; 49:3138-47. [PMID: 20192272 DOI: 10.1021/bi902052x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mechanism-based inhibitors such as cycloserine and gabaculine can inactivate aminotransferases via reactions of the compounds with the pyridoxal phosphate cofactor forming an irreversible adduct. The reaction is chirally specific in that any one enzyme usually only recognizes one enantiomer of the inactivator. For instance, l-aspartate aminotransferase (l-AspAT) is inactivated by 4-amino-4,5-dihydro-2-thiophenecarboxylic acid (ADTA), however, only by the S-isomer. We have now shown that d-amino acid aminotransferase (d-a-AT) is irreversibly inactivated by the R-isomer of the same compound. The X-ray crystal structure (PDB code: 3LQS ) of the inactivated enzyme shows that in the product the enzyme no longer makes a Schiff base linkage to the pyridoxal 5'-phosphate (PLP) cofactor, and instead the compound has formed a derivative of the cofactor. The adduct is similar to that formed between d-cycloserine and d-a-AT or alanine racemase (Ala-Rac) in that the thiophene ring of R-ADTA is intact and seems to be aromatic. The plane of the ring is rotated by nearly 90 degrees with respect to the plane of the pyridine ring of the cofactor, in comparison with the enzyme inactivated by cycloserine. Based on the structure of the product, the mechanism of inactivation most probably involves a transamination followed by aromatization to form an aromatic thiophene ring.
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Affiliation(s)
- Bryan W Lepore
- Graduate Program in Bioorganic Chemistry, Graduate Program in Biophysics and Biochemistry, Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454-9110, USA
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Fu M, Silverman RB. Inactivation of gamma-aminobutyric acid aminotransferase by (S)-4-amino-4,5-dihydro-2-furancarboxylic acid does not proceed by the expected aromatization mechanism. Bioorg Med Chem Lett 2004; 14:203-6. [PMID: 14684328 DOI: 10.1016/j.bmcl.2003.09.065] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Inactivation of pyridoxal 5'-phosphate (PLP)-dependent gamma-aminobutryic acid aminotransferase by (S)-4-amino-4,5-dihydro-2-furancarboxylic acid (SADFA) gives pyridoxamine 5'-phosphate, not the expected SADFA-PLP aromatization product. Inactivation appears to proceed by a Michael addition/hydrolysis mechanism instead.
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Affiliation(s)
- Mengmeng Fu
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
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Abstract
Pyridoxal phosphate (PLP)-dependent enzymes are unrivaled in the diversity of reactions that they catalyze. New structural data have paved the way for targeted mutagenesis and mechanistic studies and have provided a framework for interpretation of those results. Together, these complementary approaches yield new insight into function, particularly in understanding the origins of substrate and reaction type specificity. The combination of new sequences and structures enables better reconstruction of their evolutionary heritage and illuminates unrecognized similarities within this diverse group of enzymes. The important metabolic roles of many PLP-dependent enzymes drive efforts to design specific inhibitors, which are now guided by the availability of comprehensive structural and functional databases. Better understanding of the function of this important group of enzymes is crucial not only for inhibitor design, but also for the design of improved protein-based catalysts.
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Affiliation(s)
- Andrew C Eliot
- Department of Chemistry University of California, Berkeley, California 94720-3206, USA.
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Zhang J, Blazecka PG, Davidson JG. First direct reductive amination of mucochloric acid: a simple and efficient method for preparing highly functionalized alpha,beta-unsaturated gamma-butyrolactams. Org Lett 2003; 5:553-6. [PMID: 12583767 DOI: 10.1021/ol0274662] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] The first direct reductive amination of mucochloric acid (1) has been accomplished. Reaction of 1 with various alkyl, aryl, and benzylamines, followed by reduction in the same pot, provides an efficient method of obtaining N-benzyl-3,4-dichloro-1,5-dihydro-pyrrol-2-one and N-aryl (or alkyl)-3,4-dichloro-1,5-dihydro-pyrrol-2-ones.
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Affiliation(s)
- Ji Zhang
- Chemical Research and Development, Pfizer Global Research & Development, Ann Arbor Laboratories, Pfizer, Inc., 2800 Plymouth Road, Ann Arbor, Michigan 48105, USA.
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Kiryanov AA, Seed AJ, Sampson P. Ring fluorinated thiophenes: applications to liquid crystal synthesis. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(01)01951-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Five-Membered Ring Systems: Thiophenes & Se, Te Analogs. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0959-6380(00)80008-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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