Contribution of amino acid residue 208 in the hydrophobic binding site to the catalytic mechanism of human glutathione transferase A1-1.
Glutathione transferases (GSTs) catalyze the nucleophilic attack of the thiolate of glutathione on a variety of noxious, often hydrophobic, electrophiles. The interactions responsible for the binding of glutathione have been deduced in great detail from the 3-dimensional structures that have been solved for three different GSTs, each a member of a distinct structural class. However, the interactions of the electrophilic substrates with these enzymes are still largely unexplored. The contribution of the active-site Met208 to aromatic and benzylic chloride substitution reactions catalyzed by human class Alpha GST A1-1 has been evaluated by comparison of wild-type enzyme with variants mutated in position 208. The results show that the amino acid residue at position 208 primarily affects the aromatic substitution reaction, tested with 1-chloro-2,4-dinitrobenzene as substrate, possibly by interacting with the delocalized negative charge of the substituted ring structure in the transition state.
Widersten
M
M
Department of Biochemistry, Uppsala University, Sweden.
Björnestedt
R
R
Mannervik
B
B
D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes; D007700:Kinetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011994:Recombinant Proteins / Q000378:metabolism; D017421:Sequence Analysis; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D007527:Isoenzymes; D011994:Recombinant Proteins; D005982:Glutathione Transferase; C119995:glutathione S-transferase alpha