Kinetic studies on the inhibition of GABA-T by γ-vinyl GABA and taurine

S. A J Sulaiman, F. E O Suliman*, Samira Barghouthi

*Corresponding author for this work

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

γ-Aminobutyric acid transaminase (GABA-T, EC 2.6.1.19) is a pyridoxal phosphate (PLP) dependent enzyme that catalyzes the degradation of γ-aminobutyric acid. The kinetics of this reaction are studied in vitro, both in the absence, and in the presence of two inhibitors: γ-vinyl GABA (4-aminohex-5-enoic acid), and a natural product, taurine (ethylamine-2-sulfonic acid). A kinetic model that describes the transamination process is proposed. GABA-T from Pseudomonas fluorescens is inhibited by γ-vinyl GABA and taurine at concentrations of 51.0 and 78.5 mM. Both inhibitors show competitive inhibition behavior when GABA is the substrate and the inhibition constant (Ki) values for γ-vinyl GABA and taurine were found to be 26 ± 3 mM and 68 ± 7 mM respectively. The transamination process of α-ketoglutarate was not affected by the presence of γ-vinyl GABA, whereas, taurine was a noncompetitive inhibitor of GABA-T when α-ketoglutarate was the substrate. The inhibition dissociation constant (Kii) for this system was found to be 96 ± 10 mM. The Michaelis-Menten constant (Km) in the absence of inhibition, was found to be 0.79 ± 0.11 mM, and 0.47 ± 0.10 mM for GABA and α-ketoglutarate respectively.

Original languageEnglish
Pages (from-to)297-301
Number of pages5
JournalJournal of Enzyme Inhibition and Medicinal Chemistry
Volume18
Issue number4
DOIs
Publication statusPublished - Aug 2003

Keywords

  • γ-aminobutyric acid transaminase (GABA-T)
  • γ-vinyl GABA (4-aminohex-5-enoic acid)
  • Inhibitors
  • Kinetics
  • Taurine (ethylamine-2-sulfonic acid)

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

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