Kinetics of inactivation of 4-aminobutyrate aminotransferase by 3-bromopyruvate.
3-Bromopyruvate inhibited 4-aminobutyrate aminotransferase (EC 2.6.1.19) from Pseudomonas fluorescens, apparently irreversibly. Kinetics of this inactivation were studied by continuously monitoring the enzyme reaction at 30 degrees C in the presence of inhibitor. Irrespective of how high an inhibitor concentration was present, a maximum rate of inactivation was eventually achieved (5.9 x 10(-3) s-1), indicating the formation of a reversible inhibitor-enzyme complex before the final inactivation step. The dissociation constant of this complex was found to be 6.5 microM. This affinity labelling by 3-bromopyruvate suggests the presence of essential sulphydryl groups on the enzyme, since this compound is known to preferentially alkylate cysteinyl residues.
Blessinger
K J
KJ
Laboratory of Neurochemistry, Indiana University School of Medicine, Evansville 47712.
Tunnicliff
G
G
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors*; D000445:Aldehyde Oxidoreductases / Q000032:analysis; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors*; D007656:Ketoglutaric Acids / Q000494:pharmacology; D007700:Kinetics; D011551:Pseudomonas fluorescens; D011773:Pyruvates / Q000494:pharmacology*; D050644:Succinate-Semialdehyde Dehydrogenase; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D001426:Bacterial Proteins; D007656:Ketoglutaric Acids; D011773:Pyruvates; D005680:gamma-Aminobutyric Acid; C017092:bromopyruvate; D000445:Aldehyde Oxidoreductases; D050644:Succinate-Semialdehyde Dehydrogenase; D000612:4-Aminobutyrate Transaminase