[Mechanism of inhibition of pea chloroplast glutamine synthetase by methionine sulfoximine].
In the presence of ATP and Mg2+ L-methionine sulfoximine irreversibly inhibits homogeneous glutamine synthetase (EC 6.3.1.2) from pea chloroplasts (I0.5 = 1.0 x 10(-7) M; Ki = 6.25 . 10(-8) M. Glutamate (but not NH4Cl) exerts a protective effect, which is enhanced when glutamate and NH4Cl are simultaneously present in the reaction mixture. The inhibiting action of L-methionine sulfoximine with respect to glutamate is of a mixed type. ATP and Mg-ATP produce the same non-competitive protective effect on L-methionine sulfoximine. The data obtained suggest that the formation of a quaternary complex (or a transition state) between the enzyme and all its substrates is essential for the catalysis.
D002736:Chloroplasts / Q000201:enzymology*; D005974:Glutamate-Ammonia Ligase / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008717:Methionine Sulfoximine / Q000494:pharmacology*; D010944:Plants / Q000201:enzymology; D011485:Protein Binding
D008717:Methionine Sulfoximine; D005974:Glutamate-Ammonia Ligase
Mekhanizm ingibirovaniia glutaminsintetazy khloroplastov gorokha metioninsul'foksiminom.