Chapter 4 Roles of γ-Glutamyl Transpeptidase and γ-Glutamyl Cyclotransferase in Glutathione and Glutathione-Conjugate Metabolism in Plants

Ohkama‐Ohtsu, Naoko; Fukuyama, Keiichi; Oliver, David J.

doi:10.1016/s0065-2296(10)52004-4

Cited by 15 publications

(10 citation statements)

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“…GGT catalyzes the initial step of the degradation of extracellular GSH into its constituent amino acids, which are then transported into the cell and reused as a cysteine source [1,3–5]. The localization of GGT differs by organism: in bacteria, GGT is expressed in the periplasmic space or secreted into the extracellular environment [1]; in mammalian cells, it is bound to the external surface of the plasma membrane [1,5]; and in plants, it is localized to the apoplast and the vacuole [6].…”

Section: Introductionmentioning

confidence: 99%

Crystal structure of the halotolerant γ‐glutamyltranspeptidase from Bacillus subtilis in complex with glutamate reveals a unique architecture of the solvent‐exposed catalytic pocket

et al. 2010

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γ‐Glutamyltranspeptidase (GGT; EC 2.3.2.2), an enzyme found in organisms from bacteria to mammals and plants, plays a central role in glutathione metabolism. Structural studies of GGTs from Escherichia coli and Helicobacter pylori have revealed detailed molecular mechanisms of catalysis and maturation. In these two GGTs, highly conserved residues form the catalytic pockets, conferring the ability of the loop segment to shield the bound γ‐glutamyl moiety from the solvent. Here, we have examined the Bacillus subtilis GGT, which apparently lacks the amino acids corresponding to the lid‐loop that are present in mammalian and plant GGTs as well as in most bacterial GGTs. Another remarkable feature of B. subtilis GGT is its salt tolerance; it retains 86% of its activity even in 3 m NaCl. To better understand these characteristics of B. subtilis GGT, we determined its crystal structure in complex with glutamate, a product of the enzymatic reaction, at 1.95 Å resolution. This structure revealed that, unlike the E. coli and H. pylori GGTs, the catalytic pocket of B. subtilis GGT has no segment that covers the bound glutamate; consequently, the glutamate is exposed to solvent. Furthermore, calculation of the electrostatic potential showed that strong acidic patches were distributed on the surface of the B. subtilis GGT, even under high‐salt conditions, and this may allow the protein to remain in the hydrated state and avoid self‐aggregation. The structural findings presented here have implications for the molecular mechanism of GGT. Structured digital abstract http://mint.bio.uniroma2.it/mint/search/interaction.do?interactionAc=MINT-7383558: GGT (uniprotkb:http://www.uniprot.org/uniprot/P54422?format=text&ascii) and GGT (uniprotkb:http://www.uniprot.org/uniprot/P54422?format=text&ascii) bind (http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0407) by X‐ray crystallography (http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0114)

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Section: Introductionmentioning

confidence: 99%

Crystal structure of the halotolerant γ‐glutamyltranspeptidase from Bacillus subtilis in complex with glutamate reveals a unique architecture of the solvent‐exposed catalytic pocket

et al. 2010

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“…Additionally, radish has three at least GGT enzymes (Nakano et al, 2006b) of which RsGGT3 is the closest match to VvGGT3 ( Figure 1 ). When over-expressed in tobacco, RsGGT3 unlike RsGGT1 and RsGGT2 which are most likely bound to cell walls was able to be purified from the soluble fraction (Nakano et al, 2006b), suggesting that it too like AtGGT4 may be localized to the vacuole (Ohkama-Ohtsu et al, 2009). Removal of the putative N-terminal leader/targeting peptides and reconstruction of the phylogenetic tree does not substantially affect the sequence relationships observed ( Supplementary Figure 1 ).…”

Section: Resultsmentioning

confidence: 99%

“…In Arabidopsis thaliana ( Arabidopsis ), where plant GGTs have been most extensively studied, four GGT genes have been identified, of which three are functional ( AtGGT1 , AtGGT2 , and AtGGT4 ) (Grzam et al, 2007; Martin et al, 2007; Ohkama-Ohtsu et al, 2007a; Tolin et al, 2013). AtGGT3 lacks segments of exons which possess catalytic activity and is most likely a pseudogene (Ohkama-Ohtsu et al, 2009). AtGGT1 and AtGGT2 are located in the apoplast, ionically-bound to the cell wall and/or plasma membrane, as they could only be liberated with high-salt treatments (Ohkama-Ohtsu et al, 2007a; Giaretta et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…AtGGT1 and AtGGT2 are located in the apoplast, ionically-bound to the cell wall and/or plasma membrane, as they could only be liberated with high-salt treatments (Ohkama-Ohtsu et al, 2007a; Giaretta et al, 2017). Both are proposed to be involved in the prevention of oxidative stress by degrading the oxidized form of glutathione (GSSG) (Ohkama-Ohtsu et al, 2009; Noctor et al, 2012). AtGGT1 is expressed throughout the plant with expression predominantly found in leaves and the vascular system, whereas AtGGT2 is not transcribed in leaves but is specifically transcribed in GSH sink tissues such as seeds, pollen, and trichomes, AtGGT2 is also weakly transcribed in roots (Martin et al, 2007; Destro et al, 2011; Giaretta et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Functional Characterization of the Grapevine γ-Glutamyl Transferase/Transpeptidase (E.C. 2.3.2.2) Gene Family Reveals a Single Functional Gene Whose Encoded Protein Product Is Not Located in Either the Vacuole or Apoplast

2019

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γ-glutamyl transferases/transpeptidases (E.C. 2.3.2.2, GGTs) are involved in the catabolism of many compounds that are conjugated to glutathione (GSH), which have a variety of roles. GSH can act as storage and transport vehicle for reduced sulfur; it is involved in the detoxification of xenobiotics and also acts as a redox buffer by utilizing its thiol residue to protect against reactive oxygen species, which accumulate in response to biotic and abiotic stress. Furthermore, many distinctive flavor and aroma compounds in Sauvignon blanc wines originate from odorless C5- and C6-GSH conjugates or their GGT catabolized derivatives. These precursors are then processed into their volatile forms by yeast during fermentation. In many plant species, two or more isoforms of GGTs exist that target GSH-conjugates to either the apoplast or the vacuole. A bioinformatics approach identified multiple GGT candidates in grapevine (Vitis vinifera). However, only a single candidate, VvGGT3, has all the conserved residues needed for GGT activity. This is intriguing given the variety of roles of GSH and GGTs in plant cells. Characterization of VvGGT3 from cv. Sauvignon blanc was then undertaken. The VvGGT3 transcript is present in roots, leaves, inflorescences, and tendril and at equal abundance in the skin, pulp, and seed of mature berries and shows steady accumulation over the course of whole berry development. In addition, the VvGGT3 transcript in whole berries is upregulated upon Botrytis cinerea infection as well as mechanical damage to leaf tissue. VvGGT3-GFP fusion proteins transiently over-expressed in onion cells were used to study subcellular localization. To confirm VvGGT3 activity and localization in vivo, the fluorescent γ-glutamyl-7-amido-4-methylcoumarin substrate was added to Nicotiana benthamiana leaves transiently over-expressing VvGGT3. In combination, these results suggest that the functional VvGGT3 is associated with membrane-like structures. This is not consistent with its closely related functionally characterized GGTs from Arabidopsis, radish and garlic.

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“…Another crucial role of GGT is to cleave glutathione-Sconjugates as a key step in the detoxification of xenobiotics and drug metabolism (Taniguchi & Ikeda, 1998). GGTs are found in all kingdoms of life, but their in vivo localization, and perhaps accordingly their physiological roles, differ significantly depending on the organisms; for example, in bacteria GGT is expressed in the periplasmic space or is secreted into the extracellular environment (Tate & Meister, 1981), while in mammalian cells it is bound to the external surface of the plasma membrane (Taniguchi & Ikeda, 1998) and in plants it is localized to the apoplast and the vacuole (Ohkama-Ohtsu et al, 2009). Mammalian GGT orthologues share high sequence identities (i.e.…”

Section: Introductionmentioning

confidence: 99%

Structure ofBacillus subtilisγ-glutamyltranspeptidase in complex with acivicin: diversity of the binding mode of a classical and electrophilic active-site-directed glutamate analogue

Ida

Suzuki

Fukuyama

et al. 2014

Acta Cryst D Biol Crystallogr

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γ-Glutamyltranspeptidase (GGT) is an enzyme that plays a central role in glutathione metabolism, and acivicin is a classical inhibitor of GGT. Here, the structure of acivicin bound toBacillus subtilisGGT determined by X-ray crystallography to 1.8 Å resolution is presented, in which it binds to the active site in a similar manner to that inHelicobacter pyloriGGT, but in a different binding mode to that inEscherichia coliGGT. InB. subtilisGGT, acivicin is bound covalently through its C3 atom withsp2hybridization to Thr403 Oγ, the catalytic nucleophile of the enzyme. The results show that acivicin-binding sites are common, but the binding manners and orientations of its five-membered dihydroisoxazole ring are diverse in the binding pockets of GGTs.

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Chapter 4 Roles of γ-Glutamyl Transpeptidase and γ-Glutamyl Cyclotransferase in Glutathione and Glutathione-Conjugate Metabolism in Plants

Cited by 15 publications

References 81 publications

Crystal structure of the halotolerant γ‐glutamyltranspeptidase from Bacillus subtilis in complex with glutamate reveals a unique architecture of the solvent‐exposed catalytic pocket

Crystal structure of the halotolerant γ‐glutamyltranspeptidase from Bacillus subtilis in complex with glutamate reveals a unique architecture of the solvent‐exposed catalytic pocket

Functional Characterization of the Grapevine γ-Glutamyl Transferase/Transpeptidase (E.C. 2.3.2.2) Gene Family Reveals a Single Functional Gene Whose Encoded Protein Product Is Not Located in Either the Vacuole or Apoplast

Structure ofBacillus subtilisγ-glutamyltranspeptidase in complex with acivicin: diversity of the binding mode of a classical and electrophilic active-site-directed glutamate analogue

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