Functional and structural roles of the glutathione-binding residues in maize (Zea mays) glutathione S-transferase I

Labrou, Nikolaos E.; Mello, Luciane V.; Clonis, Yannis D.

doi:10.1042/0264-6021:3580101

Cited by 55 publications

(68 citation statements)

References 57 publications

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“…In mammalian alpha, pi and mu GSTs a tyrosine residue performs this function, whereas in all the plant enzymes this residue is replaced with a serine. For example, in ZmGSTF1-1 the effect of this hydrogen-bonding activation is to lower the dissociation constant (pKa) of the thiol from 8.7 to 6.2 [37]. In contrast, the beta GSTs have a cysteine in place of the serine/tyrosine residue; this promotes the formation of mixed disulphides with GSH, resulting in a very different catalytic activity from that of the other GSTs.…”

Section: Enzymatic Mechanismmentioning

confidence: 99%

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Plant Glutathione Transferases

Edwards¹,

Dixon²

2005

Methods in Enzymology

229

159

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SummaryThe soluble glutathione transferases (GSTs, EC 2.5.1.18) are encoded by a large and diverse gene family in plants, which can be divided on the basis of sequence identity into the phi, tau, theta, zeta and lambda classes. The theta and zeta GSTs have counterparts in animals but the other classes are plantspecific and form the focus of this article. The genome of Arabidopsis thaliana contains 48 GST genes, with the tau and phi classes being the most numerous. The GST proteins have evolved by gene duplication to perform a range of functional roles using the tripeptide glutathione (GSH) as a cosubstrate or coenzyme. GSTs are predominantly expressed in the cytosol, where their GSHdependent catalytic functions include the conjugation and resulting detoxification of herbicides, the reduction of organic hydroperoxides formed during oxidative stress and the isomerization of maleylacetoacetate to fumarylacetoacetate, a key step in the catabolism of tyrosine. GSTs also have non-catalytic roles, binding flavonoid natural products in the cytosol prior to their deposition in the vacuole. Recent studies have also implicated GSTs as components of ultraviolet-inducible cell signaling pathways and as potential regulators of apoptosis. Although sequence diversification has produced GSTs with multiple functions, the structure of these proteins has been highly conserved. The GSTs thus represent an excellent example of how protein families can diversify to fulfill multiple functions while conserving form and structure.

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Section: Enzymatic Mechanismmentioning

confidence: 99%

“…From what is known of the enzyme kinetics of the glutathione conjugation of model xenobiotic substrates, the reactions would be anticipated to undergo a random sequential two-substrate, two-product mechanism with the overall reaction rate being determined by the rate of release of reaction product from the active site [37].…”

Section: Enzymatic Mechanismmentioning

confidence: 99%

Plant Glutathione Transferases

Edwards¹,

Dixon²

2005

Methods in Enzymology

229

159

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“…In particular, GPxs contain a selenocysteine, which reacts covalently with GSH, generally via a ping-pong enzyme reaction mechanism [50]. In contrast, GSTs use a conserved tyrosine, serine or cysteine residue to interact with the thiol group of GSH, thus increasing the reactivity of GSH, typically via a sequential mechanism [51][52][53]. In S. cerevisiae, the two GSTs that have been identified show activity towards CDNB, but do not possess peroxidase activity [54].…”

Section: Ure2 As a Glutathione Transferasementioning

confidence: 99%

The yeast prion protein Ure2: Structure, function and folding

Lian

Jiang

Zhang

et al. 2006

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

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The Saccharomyces cerevisiae protein Ure2 functions as a regulator of nitrogen metabolism and as a glutathione-dependent peroxidase. Ure2 also has the characteristics of a prion, in that it can undergo a heritable conformational change to an aggregated state; the prion form of Ure2 loses the regulatory function, but the enzymatic function appears to be maintained. A number of factors are found to affect the prion properties of Ure2, including mutation and expression levels of molecular chaperones, and the effect of these factors on structure and stability are being investigated. The relationship between structure, function and folding for the yeast prion Ure2 are discussed.

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“…Significantly, all four classes of plant GSTs identified to date contain a conserved serine residue within their active site which is central to stabilizing the charged thiolate form of GSH used to drive conjugation and peroxidase and isomerase reactions (11). In this respect, although the reactions driven by these enzymes are diverse, their mechanism of catalysis remains essentially conserved (12).…”

mentioning

confidence: 99%

Functional Divergence in the Glutathione Transferase Superfamily in Plants

Dixon

Davis

Edwards

2002

Journal of Biological Chemistry

367

161

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Searches with the human Omega glutathione transferase (GST) identified two outlying groups of the GST superfamily in Arabidopsis thaliana which differed from all other plant GSTs by containing a cysteine in place of a serine at the active site. One group consisted of four genes, three of which encoded active glutathionedependent dehydroascorbate reductases (DHARs). Two DHARs were predicted to be cytosolic, whereas the other contained a chloroplast targeting peptide. The DHARs were also active as thiol transferases but had no glutathione conjugating activity. Unlike most other GSTs, DHARs were monomeric. The other class of GST comprised two genes termed the Lambda GSTs (GSTLs). The recombinant GSTLs were also monomeric and had glutathione-dependent thiol transferase activity. One GSTL was cytosolic, whereas the other was chloroplasttargeted. When incubated with oxidized glutathione, the putative active site cysteine of the GSTLs and cytosolic DHARs formed mixed disulfides with glutathione, whereas the plastidic DHAR formed an intramolecular disulfide. DHAR S-glutathionylation was consistent with a proposed catalytic mechanism for dehydroascorbate reduction. Roles for the cytosolic DHARs and GSTLs as antioxidant enzymes were also inferred from the induction of the respective genes following exposure to chemicals and oxidative stress.

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Functional and structural roles of the glutathione-binding residues in maize (Zea mays) glutathione S-transferase I

Cited by 55 publications

References 57 publications

Plant Glutathione Transferases

Plant Glutathione Transferases

The yeast prion protein Ure2: Structure, function and folding

Functional Divergence in the Glutathione Transferase Superfamily in Plants

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