Compounds that inactive gamma-aminobutyric acid (GABA) transaminase have been shown to exhibit anticonvulsant activity. The mechanism of inactivation of GABA transaminase by 4-amino -5-fluoro-3-phenylpentanoic acid, gamma-vinyl GABA, gamma- ethynyl GABA, ethanolamine O-sulfate, (E)-4-amino-5-fluoro-2- pentenoic acid, (Z)-4-amino-2-fluoro-2-butenoic acid, and (Z)-4- amino-2-bromo-2-butenoic acid will be determined. (3H) Pyridoxal 5'-phosphate-reconstituted apo-GABA transamianse will be used to elucidate the structure of the inactivator adduct and to determine if an enamine mechanism is involved. A large scale synthesis of (3R, 4S)- and (3S, 4R)-4-amino-5-fluoro-3- phenylpentanoic acid will be carried out for use in several in vivo experiments. 2-Phenylisogabaculine will be synthesized, its inactivation of GABA transaminase studied, its specificity for the enzyme determined, and its in vivo effect examined. The mechanism of inactivation of GABA transaminase by beta- hydrazinopropionate will be investigated with the use of model studies and enzymatically. Experiments have been devised to determine why beta-halo GABA analogues are substrates, but not inactivators of GABA transaminase. This will involve the synthesis of new GABA analogues and the testing of their ability to inactivate the enzyme. A chemical model study for the enamine inactivation mechanism of PLP enzymes also is proposed. New mechanisms for inactivation of GABA transaminase by cycloserine will be tested. On mechanism, which involves aromatization of the inactivator, is used as the basis for the design of new mechanism-based inactivators of the enzyme. 4- Amino-2-difluoromethyl-2-butenoic acid will be synthesized as an activated form of the monofluoro analogue, and its inactivation properties studied. (R)- and (S)-4-Amino-2-hydroxymethyl- butanoic acids will be synthesized in order to determine the importance of the 2,3-double bond and the hydroxyl group in the potent inhibitor, (E)-4-Amino-2-hydroxymethyl-butanoic acids will be synthesized in order to determine the importance of the 2,3- double bond and the hydroxyl group in the potent inhibitor, (E)-4- amino-2-hydroxymethyl-2-butenoic acid. 1-(Aminomethyl) cyclopropanecarboxylic acid will be synthesized and tested as a mechanism-based inactivators of GABA transaminase, namely, 3- ethynyl-, 3-vinyl-, and 3-fluoromethyl-3-aminopropylsulfonate and -phosphonate, will be synthesized and tested.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS015703-11
Application #
3396433
Study Section
Physical Biochemistry Study Section (PB)
Project Start
1979-08-01
Project End
1992-07-31
Budget Start
1989-08-01
Budget End
1990-07-31
Support Year
11
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Type
Schools of Arts and Sciences
DUNS #
City
Evanston
State
IL
Country
United States
Zip Code
60208
Wang, Zhiyong; Silverman, Richard B (2004) Synthesis of cyclopropane isosteres of the antiepilepsy drug vigabatrin and evaluation of their inhibition of GABA aminotransferase. J Enzyme Inhib Med Chem 19:293-301
Storici, Paola; De Biase, Daniela; Bossa, Francesco et al. (2004) Structures of gamma-aminobutyric acid (GABA) aminotransferase, a pyridoxal 5'-phosphate, and [2Fe-2S] cluster-containing enzyme, complexed with gamma-ethynyl-GABA and with the antiepilepsy drug vigabatrin. J Biol Chem 279:363-73
Pan, Yue; Calvert, Kristi; Silverman, Richard B (2004) Conformationally-restricted vigabatrin analogs as irreversible and reversible inhibitors of gamma-aminobutyric acid aminotransferase. Bioorg Med Chem 12:5719-25
Fu, Mengmeng; Silverman, Richard B (2004) 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 14:203-6
Pan, Yue; Qiu, Jian; Silverman, Richard B (2003) Design, synthesis, and biological activity of a difluoro-substituted, conformationally rigid vigabatrin analogue as a potent gamma-aminobutyric acid aminotransferase inhibitor. J Med Chem 46:5292-3
Choi, Sun; Silverman, Richard B (2002) Inactivation and inhibition of gamma-aminobutyric acid aminotransferase by conformationally restricted vigabatrin analogues. J Med Chem 45:4531-9
Choi, Sun; Storici, Paola; Schirmer, Tilman et al. (2002) 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 124:1620-4
Qiu, J; Silverman, R B (2000) A new class of conformationally rigid analogues of 4-amino-5-halopentanoic acids, potent inactivators of gamma-aminobutyric acid aminotransferase. J Med Chem 43:706-20
Koo, Y K; Nandi, D; Silverman, R B (2000) The multiple active enzyme species of gamma-aminobutyric acid aminotransferase are not isozymes. Arch Biochem Biophys 374:248-54
Qiu, J; Stevenson, S H; O'Beirne, M J et al. (1999) 2,6-Difluorophenol as a bioisostere of a carboxylic acid: bioisosteric analogues of gamma-aminobutyric acid. J Med Chem 42:329-32

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