Syntheses of (Z)- and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid and their inactivation of γ-aminobutyric acid aminotransferase

Theodore R. Johnson, Richard B Silverman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

(Z)- and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid (4Scheme 1Proposed mechanism of inactivation of GABA-AT by 1 or 4.Scheme 2Synthesis of 4 and 5. (i) Zn, CO2, DMF; (ii) aq. HCl; (iii) (CH3)2C=CH2, concd H2SO4, CH2Cl2; (iv) KOH, EtOH; (v) allyl bromide, DMF, 100°C; (vi) O3, -78°C, CH2Cl2; (vii) Me2S; (viii) Zn-Cu, Ac2O, 4 A molecular sieves, THF, 66°C; (ix) C18 reversed-phase HPLC; (x) TFA, CH2Cl2; (xi) Dowex 50.Scheme 3Proposed mechanism of inactivation of GABA-AT by 4 with release of activated species. and 5, respectively) were synthesized and investigated as potential mechanism-based inactivators of γ-aminobutyric acid aminotransferase (GABA-AT) in a continuing effort to map the active site of this enzyme. The core α-trifluoromethyl-α,β-unsaturated ester moiety was prepared via a Reformatsky/reductive elimination coupling of the key intermediates tert-butyl 2,2-dichloro-3,3,3-trifluoropropionate and N,N-bis(tert-butoxycarbonyl)glycinal. Both 4 and 5 inhibited GABA-AT in a time-dependent manner, but displayed non-pseudo-first-order inactivation kinetics; initially, the inactivation rate increased with time. Further investigation demonstrated that the actual inactivator is generated enzymatically from 4 or 5. This inactivating species is released from the active site prior to inactivation, and as a result, 4 and 5 cannot be defined as mechanism-based inactivators. Furthermore, 4 and 5 are alternate substrates for GABA-AT, transaminated by the enzyme with K(m) values of 0.74 and 20.5 mM, respectively. Transamination occurs approximately 276 and 305 times per inactivation event for 4 and 5, respectively. The enzyme also catalyzes the elimination of the fluoride ion from 4 and 5. A mechanism to account for these observations is proposed. Copyright (C) 1999 Elsevier Science Ltd.

Original languageEnglish (US)
Pages (from-to)1625-1636
Number of pages12
JournalBioorganic and Medicinal Chemistry
Volume7
Issue number8
DOIs
StatePublished - Aug 1 1999

Keywords

  • Amino acids and derivatives
  • Mechanism-based inactivation
  • γ-aminobutyric acid aminotransferase

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Pharmaceutical Science
  • Drug Discovery
  • Clinical Biochemistry
  • Organic Chemistry

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