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Screening for recombinant glutathione transferases active with monochlorobimane
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Biochemistry.
2002 In: Analytical Biochemistry, Vol. 309, 102-108 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2002. Vol. 309, 102-108 p.
URN: urn:nbn:se:uu:diva-94756OAI: oai:DiVA.org:uu-94756DiVA: diva2:168727
Available from: 2006-08-31 Created: 2006-08-31Bibliographically approved
In thesis
1. Role of Multiple Glutathione Transferases in Bioactivation of Thiopurine Prodrugs: Studies of Human Soluble Glutathione Transferases from Alpha, Kappa, Mu, Omega, Pi, Theta, and Zeta Classes
Open this publication in new window or tab >>Role of Multiple Glutathione Transferases in Bioactivation of Thiopurine Prodrugs: Studies of Human Soluble Glutathione Transferases from Alpha, Kappa, Mu, Omega, Pi, Theta, and Zeta Classes
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A screening method was developed for identification of catalytically active enzymes in combinatorial cDNA libraries of mutated glutathione transferase (GST) derivatives expressed in E. coli. The method is based on spraying monochlorobimane (MCB) directly over bacterial colonies growing on agar. The substrate MCB become fluorescent under UV light, when the bacterial colony contains active GSTs catalyzing the conjugation with endogenous glutathione. Eleven out of twelve GSTs investigated where active with MCB. This method can be used to screen libraries generated from most cytosolic GSTs in the search for proteins with altered functions and structures. Azathioprine (Aza), a thiopurine that has been used clinically for 40 years was investigated with 14 GSTs. Three enzymes showed prominent catalytic activities with Aza and all of them are highly expressed in the liver. We estimated the contribution of the three enzymes GSTs A1-1, A2-2 and M1-1 bioactivation of Aza in the liver and concluded that it was about 2 orders of magnitude more effective than the uncatalyzed reaction. GST bioactivation of Aza could clarify aspects of idiosyncratic reactions observed in some individuals. Two other thiopurine prodrugs, cis-acetylvinylthiopurine (cAVTP) and trans-acetylvinylthioguanine (tAVTG), were investigated with the same 14 GSTs. The results displayed diverse catalytic activities. A mechanism of consecutive reactions was proposed. The studies contribute to knowledge under what conditions the drug should optimally be administered. A study of the same prodrugs with several mutants from the Mu class characterized by a point mutation of a hypervarible residue. We conclude that the effects of the mutations were qualitatively parallel for cAVTP and tAVTG, but they vary significantly in magnitude; steric hindrance may interfere with transition-state stabilization. From the evolutionary perspective the data show that a point mutation can alternatively enhance or attenuate the activity with a particular substrate and illustrate the functional plasticity of GSTs.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 47 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 208
Biochemistry, Glutathione Transferases, Thiopurines, Prodrug, Bioactivation, Screening Method, Chemotherapy, Functional plasticity, Modulated activity, Biokemi
urn:nbn:se:uu:diva-7102 (URN)91-554-6630-3 (ISBN)
Public defence
2006-09-22, B21, BMC, Husarg 3, Uppsala, 10:15
Available from: 2006-08-31 Created: 2006-08-31 Last updated: 2011-07-18Bibliographically approved

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