title: Mechanism of inactivation of gamma-aminobutyrate aminotransferase by 4-amino-5-fluoropentanoic acid. First example of an enamine mechanism for a gamma-amino acid with a partition ratio of 0.
abstract: The mechanism of inactivation of pig brain gamma-aminobutyric acid aminotransferase (GABA-T) by (S)-4-amino-5-fluoropentanoic acid (1, R = CH2CH2COOH, X = F) previously proposed [Silverman, R. B., & Levy, M. A. (1981) Biochemistry 20, 1197-1203] is revised. apo-GABA-T is reconstituted with [4-3H]pyridoxal 5'-phosphate and inactivated with 1 (R = CH2CH2COOH, X = F). Treatment of inactivated enzyme with base followed by acid denaturation leads to the complete release of radioactivity as 6-[2-hydroxy-3-methyl-6-(phosphonoxymethyl)-4-pyridinyl]-4-oxo-5-+ ++hexenoic acid (4, R = CH2CH2COOH). Alkaline phosphatase treatment of this compound produces dephosphorylated 4 (R = CH2CH2COOH). These results support a mechanism that was suggested by Metzler and co-workers [Likos, J. J., Ueno, H., Feldhaus, R. W., & Metzler, D. E. (1982) Biochemistry 21, 4377-4386] for the inactivation of glutamate decarboxylase by serine O-sulfate (Scheme I, pathway b, R = COOH, X = OSO3-).
mesh_terms: D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors*; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology*; D010421:Pentanoic Acids / Q000494:pharmacology*; D011485:Protein Binding; D011732:Pyridoxal Phosphate / Q000378:metabolism; D013552:Swine; D014316:Tritium; D014631:Valerates / Q000494:pharmacology*
chemical_list: D010421:Pentanoic Acids; D014631:Valerates; D014316:Tritium; D011732:Pyridoxal Phosphate; C032606:4-amino-5-fluoropentanoic acid; D000612:4-Aminobutyrate Transaminase