Inhibition of octopus glutathione transferase by Meisenheimer complex analog, S-(2,4,6-trinitrophenyl) glutathione.
The tight binding of Meisenheimer intermediate with octopus digestive gland glutathione transferase was analyzed with 1,3,5-trinitrobenzene, which forms a trapped Meisenheimer complex with glutathione because there is no leaving group at the ipso carbon. By steady-state enzyme kinetic analysis, an inhibition constant of 1.89 +/- 0.17 microM was found for the transient formed, S-(2,4,6-trinitrophenyl) glutathione. The above inhibition constant is 407-fold smaller than the Km value for the substrate (2,4-dinitrochlorobenzene). Thus, S-(2,4,6-trinitrophenyl) glutathione is considered to be a transition-state analog. The tight binding of this inhibitor to the enzyme provides an explanation for the involvement of the biological binding effect on the rate enhancement in the glutathione transferase-catalyzed SNAr mechanism.
Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan.
J Y
JY
Liou
T M
TM
Huang
G G
GG
Chang
D000818:Animals; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D049831:Octopodiformes / Q000201:enzymology*; D011485:Protein Binding; D013379:Substrate Specificity; D014301:Trinitrobenzenes / Q000378:metabolism / Q000494:pharmacology
D014301:Trinitrobenzenes; C029222:sym-trinitrobenzene; C049220:2,4,6-trinitrophenylglutathione; D005982:Glutathione Transferase; D005978:Glutathione