The Zeta class of glutathione transferases (GSTs) has only recently been discovered and hence has been poorly characterized. Here we investigate the substrate binding and kinetic mechanisms of the human Zeta class GSTZ1c-1c by means of pre-steady state and steady-state experiments and site-directed mutagenesis. Binding of GSH occurs at a very low rate compared with that observed for the more recently evolved GSTs (Alpha, Mu, and Pi classes). Moreover, the single step binding mechanism observed in this enzyme is reminiscent of that found for the Theta class enzyme, whereas the Alpha, Mu, and Pi classes have adopted a multistep binding mechanism. Replacement of Cys 16 with Ala increases the rate of GSH release from the active site causing a 10-fold decrease of affinity toward GSH. Cys16 also plays a crucial role in co-substrate binding; the mutant enzyme is unable to bind the carcinogenic substrate dichloroacetic acid in the absence of GSH. However, both substrate binding and GSH activation are not rate-limiting in catalysis. A peculiarity of the hGSTZ1c-1c is the half-site activation of bound GSH. This suggests a primitive monomer-monomer interaction that, in the recently diverged GSTP1-1, gives rise to a sophisticated cooperative mechanism that preserves the catalytic efficiency of this GST under stress conditions.

Ricci, G., Turella, P., De Maria, F., Antonini, G., Nardocci, L., Board, P.G., et al. (2004). Binding and kinetic mechanisms of the zeta class glutathione transferase. THE JOURNAL OF BIOLOGICAL CHEMISTRY, 279(32), 33336-33342 [10.1074/jbc.M404631200].

Binding and kinetic mechanisms of the zeta class glutathione transferase

RICCI, GIORGIO;FEDERICI, GIORGIO;CACCURI, ANNA MARIA
2004

Abstract

The Zeta class of glutathione transferases (GSTs) has only recently been discovered and hence has been poorly characterized. Here we investigate the substrate binding and kinetic mechanisms of the human Zeta class GSTZ1c-1c by means of pre-steady state and steady-state experiments and site-directed mutagenesis. Binding of GSH occurs at a very low rate compared with that observed for the more recently evolved GSTs (Alpha, Mu, and Pi classes). Moreover, the single step binding mechanism observed in this enzyme is reminiscent of that found for the Theta class enzyme, whereas the Alpha, Mu, and Pi classes have adopted a multistep binding mechanism. Replacement of Cys 16 with Ala increases the rate of GSH release from the active site causing a 10-fold decrease of affinity toward GSH. Cys16 also plays a crucial role in co-substrate binding; the mutant enzyme is unable to bind the carcinogenic substrate dichloroacetic acid in the absence of GSH. However, both substrate binding and GSH activation are not rate-limiting in catalysis. A peculiarity of the hGSTZ1c-1c is the half-site activation of bound GSH. This suggests a primitive monomer-monomer interaction that, in the recently diverged GSTP1-1, gives rise to a sophisticated cooperative mechanism that preserves the catalytic efficiency of this GST under stress conditions.
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore BIO/10
English
Con Impact Factor ISI
Binding energy; Carcinogens; Catalysis; Enzyme kinetics; Enzymes; Monomers; Mutagenesis; Substrates; Glutathione transferases (GST); Half-site activation; Kinetic mechanism; Monomer-monomer interactions; Biochemistry; alanine; carcinogen; cysteine; dichloroacetic acid; glutathione s transferase p1 1; glutathione transferase; glutathione transferase alpha; glutathione transferase mu; glutathione transferase P1; glutathione transferase zeta; glutathione transferase zeta1c 1c; monomer; mutant protein; unclassified drug; article; binding kinetics; catalysis; enzyme activation; enzyme active site; enzyme binding; enzyme kinetics; enzyme substrate complex; Escherichia coli; nonhuman; pre steady state; priority journal; protein protein interaction; site directed mutagenesis; steady state; stress; Binding Sites; Catalysis; Dichloroacetate; Escherichia coli; Glutathione; Glutathione Transferase; Humans; Hydrogen-Ion Concentration; Kinetics; Mutagenesis, Site-Directed; Spectrum Analysis; Structure-Activity Relationship; Substrate Specificity; Escherichia coli
Ricci, G., Turella, P., De Maria, F., Antonini, G., Nardocci, L., Board, P.G., et al. (2004). Binding and kinetic mechanisms of the zeta class glutathione transferase. THE JOURNAL OF BIOLOGICAL CHEMISTRY, 279(32), 33336-33342 [10.1074/jbc.M404631200].
Ricci, G; Turella, P; De Maria, F; Antonini, G; Nardocci, L; Board, P; Parker, M; Carbonelli, M; Federici, G; Caccuri, Am
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2108/30709
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