Mutational analysis of human glutathione transferase A2-2 identifies structural elements supporting high activity with the prodrug azathioprine
2012 (English)In: Protein Engineering Design & Selection, ISSN 1741-0126, E-ISSN 1741-0134, Vol. 25, no 4, 189-197 p.Article in journal (Refereed) Published
Glutathione transferase (GST) A2-2 is the human enzyme displaying the highest catalytic activity with the prodrug azathioprine (Aza). The reaction releases pharmacologically active 6-mercaptopurine by displacing the imidazole moiety from the Aza molecule. The GST-catalyzed reaction is of medical significance, since high rates of Aza activation may lead to adverse side effects in treated patients. The present study involves structureactivity relationships in GST A2-2 variants. Chimeric GSTs were previously generated by DNA shuffling and two peptide segments, one N-terminal and one C-terminal, were identified as primary determinants of Aza activity. The segments contain several residues of the substrate-binding H-site and their significance for supporting high Aza activity was investigated. Substitution of the corresponding two small regions in the low-activity human GST A3-3 or rat GST A3-3 by the human GST A2-2 segments generated chimeras with approximate to 10-fold enhanced Aza activity. The H-site residues Met208 and Leu213 in the C-terminal segment of GST A2-2 were mutated to produce a library with all possible residue combinations. At a calculated 93 library coverage, all of the 1880 mutants examined showed wild-type or decreased Aza activity, even though some retained activities with alternative substrates, further emphasizing the importance of this region for the targeted activity.
Place, publisher, year, edition, pages
2012. Vol. 25, no 4, 189-197 p.
directed evolution, DNA shuffling, GST, prodrug, structure-activity relationship, azathioprine, chimeric mutagenesis, glutathione transferase, prodrug activation, saturation mutagenesis
Biochemistry and Molecular Biology Biocatalysis and Enzyme Technology
IdentifiersURN: urn:nbn:se:uu:diva-167324DOI: 10.1093/protein/gzs006ISI: 000302021100006OAI: oai:DiVA.org:uu-167324DiVA: diva2:483596