Comparative analysis of two stress-inducible tau class glutathione transferases from glycine max revealed significant catalytic and structural diversification

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. the 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. © 2017 bentham science publishers.