G. Tunnicliff, CHEMICAL MODIFICATION OF BACTERIAL 4-AMINOBUTYRATE AMINOTRANSFERASE BY PHENYLGLYOXAL, Journal of enzyme inhibition, 9(4), 1995, pp. 309-316
4-Aminobutyrate aminotransferase (EC 2.6.1.19), obtained from Pseudomo
nas fluorescens, was irreversibly inhibited by phenylglyoxal, a reagen
t that specifically modifies arginyl residues. The inactivation appear
ed to be the result of a simple, bimolecular reaction since no evidenc
e of a reversible complex between inhibitor and enzyme emerged. The se
cond-order rate constant was 0.221+/-0.077 M(-1) sec(-1). The concentr
ation of either substrate had no effect on the inhibition, but an incr
ease in the concentration of pyridoxal 5'-phosphate reduced the rate o
f inactivation by phenylglyoxal. The data are consistent with the modi
fication of amino acid residues at the cofactor binding site on the en
zyme.