Chemical modification of bacterial 4-aminobutyrate aminotransferase by phenylglyoxal.
4-Aminobutyrate aminotransferase (EC 2.6.1.19), obtained from Pseudomonas fluorescens, was irreversibly inhibited by phenylglyoxal, a reagent that specifically modifies arginyl residues. The inactivation appeared to be the result of a simple, bimolecular reaction since no evidence of a reversible complex between inhibitor and enzyme emerged. The second-order rate constant was 0.221 +/- 0.077 M-1 sec-1. The concentration of either substrate had no effect on the inhibition, but an increase in the concentration of pyridoxal 5'-phosphate reduced the rate of inactivation by phenylglyoxal. The data are consistent with the modification of amino acid residues at the cofactor binding site on the enzyme.
Tunnicliff
G
G
Laboratory of Neurochemistry, Indiana University School of Medicine, Evansville 47712, USA. GTUNNIC@INDYVAX.IUPUI.EDU
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors* / Q000737:chemistry; D000445:Aldehyde Oxidoreductases / Q000187:drug effects; D001120:Arginine / Q000737:chemistry / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D010658:Phenylglyoxal / Q000737:chemistry / Q000494:pharmacology*; D011551:Pseudomonas fluorescens / Q000201:enzymology*; D050644:Succinate-Semialdehyde Dehydrogenase
D004791:Enzyme Inhibitors; D001120:Arginine; D000445:Aldehyde Oxidoreductases; D050644:Succinate-Semialdehyde Dehydrogenase; D000612:4-Aminobutyrate Transaminase; D010658:Phenylglyoxal