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Comparative Analysis of Two Stress-Inducible tau Class Glutathione Transferases from Glycine max Revealed Significant Catalytic and Structural Diversification

[ Vol. 24 , Issue. 10 ]

Author(s):

Fotini Pouliou, Fereniki Perperopoulou and Nikolaos E. Labrou*   Pages 922 - 935 ( 14 )

Abstract:


Background: Glutathione transferases (GSTs, EC. 2.5.1.18) form a large group of multifunctional enzymes that are involved in the metabolism and inactivation of a wide range of endogenous and xenobiotic compound as well as in cell regulation and response to several biotic and abiotic stresses.

Objectives: In the present work, we report the comparative analysis of the structural and functional features of two isoenzymes (GmGSTU5-5 and GmGSTU8-8) of the glutathione transferase (GST) family from Glycine max.

Methods: Full-length cDNA clones of GmGSTU5-5 and GmGSTU8-8 were derived from RT-PCR of RNA isolated from soybean seedlings and were cloned into a T7 expression vector. Τhe recombinant enzymes were expressed in E. coli and purified by affinity chromatography. Substrate specificity, kinetic and inhibition analysis were carried out towards a range of different xenobiotic compounds and GSH analogues. The thermal stability of the enzymes was also evaluated using activity assays and differential scanning fluorimetry.

Results: Analysis of substrate specificity using a range of thiol substrates and electrophilic compounds suggested that both isoenzymes display broad and overlapping specificities. They are capable of detoxifying major stress-induced toxic products. Study of their ligandin-binding properties by kinetic analysis and molecular modelling indicated that both GmGSTU5-5 and GmGSTU8-8 bind a range of secondary metabolites and plant hormones, suggesting a role in transport or storage of bioactive compounds. Thermostability analysis showed that GmGSTU5-5 and GmGSTU8-8 display extraordinary thermal stability, compared to other plant GSTs.

Conclusion: Our results suggest that GmGSTU5-5 and GmGSTU8-8 display different or overlapping substrate specificities and kinetic properties. The biological role of GmGSTU5-5 and GmGSTU8-8 may be relevant to the detoxification of toxic compounds or the binding of bioactive metabolites that function in cell regulation and stress defence mechanisms.

Keywords:

Abiotic stress, biotic stress, glutathione transferase, Glycine max, xenobiotic metabolism, isoenzymes.

Affiliation:

Laboratory of Enzyme Technology, Department of Biotechnology, School of Food, Biotechnology and Development, Agricultural University of Athens, 75 Iera Odos Street, GR-11855-Athens, Laboratory of Enzyme Technology, Department of Biotechnology, School of Food, Biotechnology and Development, Agricultural University of Athens, 75 Iera Odos Street, GR-11855-Athens, Laboratory of Enzyme Technology, Department of Biotechnology, School of Food, Biotechnology and Development, Agricultural University of Athens, 75 Iera Odos Street, GR-11855-Athens

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