A Remarkable Difference That One Fluorine Atom Confers on the Mechanisms of Inactivation of Human Ornithine Aminotransferase by Two Cyclohexene Analogues of γ-Aminobutyric Acid

Wei Zhu, Peter F. Doubleday, Daniel S. Catlin, Pathum M. Weerawarna, Arseniy Butrin, Sida Shen, Zdzislaw Wawrzak, Neil L. Kelleher, Dali Liu, Richard B. Silverman*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Human ornithine aminotransferase (hOAT), a pyridoxal 5′-phosphate-dependent enzyme, plays a critical role in the progression of hepatocellular carcinoma (HCC). Pharmacological selective inhibition of hOAT has been shown to be a potential therapeutic approach for HCC. Inspired by the discovery of the nonselective aminotransferase inactivator (1R,3S,4S)-3-amino-4-fluoro cyclopentane-1-carboxylic acid (1), in this work, we rationally designed, synthesized, and evaluated a novel series of fluorine-substituted cyclohexene analogues, thereby identifying 8 and 9 as novel selective hOAT time-dependent inhibitors. Intact protein mass spectrometry and protein crystallography demonstrated 8 and 9 as covalent inhibitors of hOAT, which exhibit two distinct inactivation mechanisms resulting from the difference of a single fluorine atom. Interestingly, they share a similar turnover mechanism, according to the mass spectrometry-based analysis of metabolites and fluoride ion release experiments. Molecular dynamics (MD) simulations and electrostatic potential (ESP) charge calculations were conducted, which elucidated the significant influence of the one-fluorine difference on the corresponding intermediates, leading to two totally different inactivation pathways. The novel addition-aromatization inactivation mechanism for 9 contributes to its significantly enhanced potency, along with excellent selectivity over other aminotransferases.

Original languageEnglish (US)
Pages (from-to)4892-4903
Number of pages12
JournalJournal of the American Chemical Society
Volume142
Issue number10
DOIs
StatePublished - Mar 11 2020

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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