Glutathione transferases catalyze the conjugation of glutathione to various electrophilic compounds. Soluble glutathione transferases make up a superfamily of evolutionarily related enzymes. Primarily, glutathione transferases catalyze nucleophilic substitution or addition reactions, but they can also act as peroxidase, isomerase, or just as binding protein sequestering hydrophobic molecules.
The "natural" substrates of glutathione transferases range from molecules of foreign origin (e.g., diol epoxides of benzo[a]pyrene), to by-products of cellular metabolism (e.g., phospholipid hydroperoxides). In addition to the electrophilic center, most substrates have in common that they are hydrophobic.
Crystal structure of human glutathione transferase T2-2 with bound products
Note the C-terminal helices that block the exits of the two active sites and probably contribute to the slow product release of the enzyme.
My work focused on the catalytic mechansim of theta-class glutathione transferases, especially rat glutathione transferase T2-2. This enzyme turned out to have a quite complicated mechanism involving slow and fast conformational changes, fast product formation and slow product release. These results, and studies on human glutathione transferase T1-1 and A1-1, are presented in detail in a number of papers in the publication list. My PhD thesis summarizes most of my work on the glutathione transferases.
Before leaving the glutathione transferase field I tried to evolve novel theta-class enzymes by breeding the human T1-1 and rat T2-2 enzymes using DNA shuffling under error-prone conditions. The work was carried on by Kerstin Broo and Anna-Karin Larsson who meritoriously characterized and evaluated the library obtained. Despite the fairly low sequence identity of the T1-1 and T2-2 isoenzymes, some recombination of the two genes had occurred, along with the random point mutations. The work is presented in:
Broo, K., Larsson, A.-K., Jemth, P., and Mannervik, B. (2002) An ensemble of theta class glutathione transferases with novel catalytic properties generated by stochastic recombination of fragments of two mammalian enzymes. J. Mol. Biol. 318, 59-70 [abstract]
Other references:
Crystal structure of human glutathione transferase T2-2:
Rossjohn, J., McKinstry, W. J., Oakley, A. J., Verger, D., Flanagan, J., Chelvanayagam, G., Tan, K. L., Board, P. G., and Parker, M. W. (1998) Human theta class glutathione transferase: the crystal structure reveals a sulfate-binding pocket within a buried active site. Structure 6, 309-322 [abstract]
Structure and catalytic mechanism of glutathione transferases (review):
Armstrong, R. N. (1997) Structure, catalytic mechanism and evolution of the glutathione transferases. Chem. Res. Toxicol. 10, 2-18 [abstract]
The evolution of glutathione transferases from a mechanistic point of view (review):
Armstrong, R. N. (1998) Mechanistic imperatives for the evolution of glutathione transferases. Curr. Opin. Chem. Biol. 2, 618-623 [abstract]