10.1021/acschembio.5b00212.s001 Hyunbeom Lee Hyunbeom Lee Hoang V. Le Hoang V. Le Rui Wu Rui Wu Emma Doud Emma Doud Ruslan Sanishvili Ruslan Sanishvili John F. Kellie John F. Kellie Phillip D. Compton Phillip D. Compton Boobalan Pachaiyappan Boobalan Pachaiyappan Dali Liu Dali Liu Neil L. Kelleher Neil L. Kelleher Richard B. Silverman Richard B. Silverman Mechanism of Inactivation of GABA Aminotransferase by (<i>E</i>)- and (<i>Z</i>)‑(1<i>S</i>,3<i>S</i>)‑3-Amino-4-fluoromethylenyl-1-cyclopentanoic Acid American Chemical Society 2015 CPP metabolite formyl group acid GABA vigabatrin inactivation future inactivator design inactivating Arg 445 2015-09-18 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Mechanism_of_Inactivation_of_GABA_Aminotransferase_by_i_E_i_and_i_Z_i_1_i_S_i_3_i_S_i_3_Amino_4_fluoromethylenyl_1_cyclopentanoic_Acid/2129971 When γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian central nervous system, falls below a threshold level, seizures occur. One approach to raise GABA concentrations is to inhibit GABA aminotransferase (GABA-AT), a pyridoxal 5′-phosphate-dependent enzyme that degrades GABA. We have previously developed (1<i>S</i>,3<i>S</i>)-3-amino-4-difluoromethylene-1-cyclopentanoic acid (CPP-115), which is 186 times more efficient in inactivating GABA-AT than vigabatrin, the only FDA-approved inactivator of GABA-AT. We also developed (<i>E</i>)- and (<i>Z</i>)-(1<i>S</i>,3<i>S</i>)-3-amino-4-fluoromethylenyl-1-cyclopentanoic acid (<b>1</b> and <b>2</b>, respectively), monofluorinated analogs of CPP-115, which are comparable to vigabatrin in inactivating GABA-AT. Here, we report the mechanism of inactivation of GABA-AT by <b>1</b> and <b>2</b>. Both produce a metabolite that induces disruption of the Glu270–Arg445 salt bridge to accommodate interaction between the metabolite formyl group and Arg445. This is the second time that Arg445 has interacted with a ligand and is involved in GABA-AT inactivation, thereby confirming the importance of Arg445 in future inactivator design.