Two pathways in the biosynthesis of cadystins (γEC)<sub><i>n</i></sub>G in the cell-free system of the fission yeast

Hayashi, Yukimasa; Nakagawa, Chiaki W.; Mutoh, Norihiro; Isobe, Mitsuaki; Goto, Toshio

doi:10.1139/o91-018

Cited by 87 publications

(57 citation statements)

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“…In the fission yeast S. pombe, two pathways for the biosynthesis of class III metallothioneins have been detected in a cell-free system (Hayashi et al, 1991). The first is similar to that described for Silene cucubalus cell cultures except that either glutathione or class III metallothioneins can act as donors for y-glutamylcysteine.…”

Section: Blosynthesismentioning

confidence: 77%

Plant metallothioneins

Robinson

Tommey

Kuske

et al. 1993

Biochemical Journal

389

257

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Section: Blosynthesismentioning

confidence: 77%

Plant metallothioneins

Robinson

Tommey

Kuske

et al. 1993

Biochemical Journal

389

257

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“…␥-Glu-Cys might directly buffer increasing intracellular metal concentrations through sulfhydryl coordination, like the structurally similar glutathione (Rabenstein 1989); perhaps in the case of Zn, these intracellular complexes are then exuded, like phytochelatin-Cd complexes (Lee et al 1996). Phytochelatins, which have been well studied in marine algae, can be synthesized from ␥-Glu-Cys in fission yeast (Hayashi et al 1991); conceivably, this is the case in E. huxleyi and some other algae and might also explain the intracellular increases in response to Cu, Cd, and Zn.…”

Section: Discussionmentioning

confidence: 99%

Effects of copper, cadmium, and zinc on the production and exudation of thiols by Emiliania huxleyi

Dupont

Ahner

2005

Limnol. Oceanogr.

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Cultures of the ubiquitous coccolithophore Emiliania huxleyi grown at field-relevant fixed free ion concentrations of Cu, Cd, and Zn exude a broad array of thiols, some of which increase with increasing metal ion concentration. The primary thiols released are contingent on the particular metal or combination of metals added to the culture media. Exposure to Cu results in the release of arginine-cysteine, glutamine-cysteine, and cysteine; Cd causes these thiols and glutathione to be released; and high Zn results in the synthesis and exudation of predominantly ␥-glutamate-cysteine (␥-Glu-Cys). Because the free ion concentrations of Cu and Cd used in these experiments are similar to those observed in the field, active exudation could be an important source of thiols to surface seawater and thus might affect trace metal speciation in the open ocean. Intracellular thiol concentrations were also clearly affected by metal concentrations, with ␥-Glu-Cys being particularly dynamic. Additionally, the shift from exponential to stationary growth in batch cultures caused approximately two-to fourfold declines in the concentrations of nearly all intracellular thiols.There is evidence that sulfur-containing compounds of low molecular mass are an important component of the pool of ligands responsible for the nearly complete complexation of (Moffett et al. 1990;Bruland et al. 1991), and culture studies have confirmed that phytoplankton have the capability of producing ligands with similar complexing strengths to those measured in the field (Moffett and Brand 1996; Leal et al. 1999;Croot et al. 2000). Specifically, Leal et al. (1999) found that high copper concentrations promoted the simultaneous release of copper-binding ligands and compounds with reduction potentials similar to those of known thiols.We identified two novel thiols produced by Emiliania huxleyi, arginine-cysteine (Arg-Cys) and glutamine-cysteine (Gln-Cys), which were present at high intracellular concentrations (Dupont et al. 2004b). These compounds, along with cysteine, were released proportionally as copper was added to the growth media. Specific thiol-Cu(I) complexes-CysCu(I), Arg-Cys-Cu(I)-Cys, and (Cys) 2 -Cu(I)-were also identified in the culture media of copper-exposed E. huxleyi with matrix-assisted laser desorption/ionization time-offlight mass spectrometry. Given that the culture techniques used in that study were designed to produce high concentrations of copper ligand complexes, it remains to be determined whether the exudation of these thiols occurs at en-1 To whom correspondence should be addressed. Present address: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093 (cdupont@ucsd.edu). AcknowledgmentsThis work was funded by an NSF grant (OCE-0002677) to B.A.A. We thank T. Goepfert for help in algal culturing and sampling and two anonymous reviewers for helpful comments and suggestions.

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“…Since coupling of As(III) to dithiols results in the formation of stable complexes, chain elongation of PCs could provide very strong binding of As. However, longer-chain PCs are produced from shorter-chain PCs (Hayashi et al, 1991) ; therefore the strong binding of As to PC # could lead to a shortage of substrate to form longer chains. This is reflected by Fig.…”

Section: mentioning

confidence: 99%

“…Phytochelatins have the structure (γ-glu-cys) n -gly, where n l 2-11 (Grill et al, 1985), and are produced in plants on exposure to a variety of heavy metals and metalloids (Gekeler et al, 1989). Phytochelatins are synthesized from GSH (Hayashi et al, 1991), the synthesis being ended if the exposure to heavy metals or metalloids is terminated (Loeffler et al, 1989), after which degradation of PCs may become apparent (De Knecht et al, 1995). Arsenic not only induces PC synthesis, it also stimulates the production of the PC precursor GSH (Li & Chou, 1992).…”

mentioning

confidence: 99%

Toxicity of arsenate in Silene vulgaris, accumulation and degradation of arsenate‐induced phytochelatins

et al. 1999

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The results presented in this paper describe the short-and long-term toxicity of arsenate in Silene vulgaris. Shortterm toxicity, measured as inhibition of root elongation, depended on phosphate nutrition, arsenate being much less toxic at high phosphate supply. At low phosphate levels more arsenic was taken up by the plants. Under chronic exposure, toxicity (measured as inhibition of biomass production) did not increase with time. In addition, the accumulation of phytochelatins (PCs) as a function of toxicity and duration of exposure was studied. Shortterm PC accumulation (over a 3 d period) was positively correlated with exposure. Isolation of peptide complexes from prolongedly exposed plants showed that PC # , PC $ and PC % were present, although the latter not until at least 3 d exposure. Arsenic co-eluted mainly with PC # and PC $ . Fractions containing PC % were devoid of As, probably due to dissociation of the complexes during extraction or elution. The breakdown of PCs after arresting As exposure was very slow. This could explain the continuous accumulation of PCs throughout longer periods of As exposure.Key words : Silene vulgaris, arsenic toxicity, arsenic detoxification, phytochelatins. Arsenic is taken up mainly by plant roots as arsenate (AsO % $−) (Macnair & Cumbes, 1987) through the phosphate-uptake system (Asher & Reay, 1979). Once the arsenate, As(V), is taken up it is reduced to arsenite, As(III), by glutathione (GSH) (Thompson, 1993). Only in phosphate-deficient conditions is arsenate subsequently methylated in plants (Nissen & Benson, 1982). Between the successive methylation steps, GSH serves to reduce the intermediate products (Scott et al., 1993 ;Thompson, 1993). Arsoniumphospholipids in freshwater plants (Nissen & Benson, 1982) and arsenic sugars in marine brown algae (Edmonds & Francesconi, 1981) have also been identified.Mostly there is little transport of As to the aboveground parts of the plants. Dicotyledonous plants appear to transport more As to the shoots than monocotyledonous plants (Otte, 1991). The form in *Author for correspondence (fax j31 20 444 7123 ; e-mail elsesnel!bio.vu.nl). which the As is transported is unknown. There is some indication that dimethylarsenic acid is transported to the shoots (Marin et al., 1993).Increased As levels may cause toxic symptoms in plants, such as a decrease in plant growth and fruit yield (Carbonell-Barrachina et al., 1995), root discoloration and root plasmolysis, wilting and necrosis of leaf tips and leaf margins (Machlis, 1941), and a decrease in photosynthetic capacity (Marin et al., 1993).Some authors have reported the accumulation of heavy metal-binding, thiol-rich phytochelatins (PCs) on exposure to As (Grill et al., 1986a(Grill et al., ,b, 1987Maitani et al., 1996). Phytochelatins have the structure (γ-glu-cys) n -gly, where n l 2-11 (Grill et al., 1985), and are produced in plants on exposure to a variety of heavy metals and metalloids (Gekeler et al., 1989). Phytochelatins are synthesized from GSH (Hayashi et ...

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Two pathways in the biosynthesis of cadystins (γEC)_nG in the cell-free system of the fission yeast

Cited by 87 publications

References 0 publications

Plant metallothioneins

Plant metallothioneins

Effects of copper, cadmium, and zinc on the production and exudation of thiols by Emiliania huxleyi

Toxicity of arsenate in Silene vulgaris, accumulation and degradation of arsenate‐induced phytochelatins

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Two pathways in the biosynthesis of cadystins (γEC)nG in the cell-free system of the fission yeast

Cited by 87 publications

References 0 publications

Plant metallothioneins

Plant metallothioneins

Effects of copper, cadmium, and zinc on the production and exudation of thiols by Emiliania huxleyi

Toxicity of arsenate in Silene vulgaris, accumulation and degradation of arsenate‐induced phytochelatins

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Two pathways in the biosynthesis of cadystins (γEC)_nG in the cell-free system of the fission yeast