Open AccessA Remarkable Difference That One Fluorine Atom Confers on the Mechanisms of Inactivation of Human Ornithine Aminotransferase by Two Cyclohexene Analogues of γ-Aminobutyric Acid
Author(s) -
Wei Zhu,
Peter F. Doubleday,
Daniel S. Catlin,
Pathum M. Weerawarna,
Arseniy Butrin,
Sida Shen,
Z. Wawrzak,
Neil L. Kelleher,
Dali Liu,
Richard B. Silverman
Publication year - 2020
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.0c00193
Subject(s) - chemistry , fluorine , enzyme , selectivity , ornithine aminotransferase , active site , stereochemistry , ornithine , biochemistry , amino acid , organic chemistry , arginine , catalysis
Human ornithine aminotransferase ( h OAT), a pyridoxal 5'-phosphate-dependent enzyme, plays a critical role in the progression of hepatocellular carcinoma (HCC). Pharmacological selective inhibition of h OAT has been shown to be a potential therapeutic approach for HCC. Inspired by the discovery of the nonselective aminotransferase inactivator (1 R ,3 S ,4 S )-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 h OAT time-dependent inhibitors. Intact protein mass spectrometry and protein crystallography demonstrated 8 and 9 as covalent inhibitors of h OAT, 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.