title: Purification and partial characterization of glutathione transferase from the teleost Monopterus albus.
abstract: Glutathione transferases (GSTs) catalyze the transfer of glutathione to a variety of xenobiotic and toxic endogenous compounds. GSTs are phase II biotransformation enzymes and are proposed as biomarkers of environmental pollution. In this study, a cytosolic glutathione transferase (maGST) was purified from liver of the freshwater fish Monopterus albus by affinity chromatography. The maGST appeared to be a homodimer composed of two subunits each with a molecular weight of 26 kDa. This maGST showed high activity towards the substrates 1-chloro-2,4-dinitrobenzene (CDNB) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl). Kinetic analysis with CDNB as substrate revealed a K(m) of 0.28 mM and V(max) of 15.68 micromol/min per mg of protein. It had maximum activity in the pH range 7.0-7.5, a broad optimum T(m) range of 30 degrees C-55 degrees C, and a high thermal stability with 77% of its initial activity at 45 degrees C. This high thermal stability of maGST could be related to the physiological adaptation of M. albus to high temperatures in tropical and subtropical environments.
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Huang
authors.forename: Li
authors.initials: L
authors.lastname: Liang
authors.forename: Tao
authors.initials: T
authors.lastname: Wei
authors.forename: Daming
authors.initials: D
authors.lastname: Zhang
authors.forename: Qing-Yin
authors.initials: QY
authors.lastname: Zeng
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000378:metabolism; D000818:Animals; D002846:Chromatography, Affinity; D019281:Dimerization; D004137:Dinitrochlorobenzene / Q000378:metabolism; D004795:Enzyme Stability; D029941:Fish Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D005982:Glutathione Transferase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D011489:Protein Denaturation; D023701:Smegmamorpha / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D004137:Dinitrochlorobenzene; D029941:Fish Proteins; D005982:Glutathione Transferase; D009327:4-Chloro-7-nitrobenzofurazan