“Glutathione-ascorbate cycle”的意思、由来-开放百科全书

The glutathione-ascorbate cycle is a metabolic pathway that detoxifies hydrogen peroxide (H₂O₂), which is a reactive oxygen species that is produced as a waste product in metabolism. The cycle involves the antioxidant metabolites: ascorbate, glutathione and NADPH and the enzymes linking these metabolites.^[1]

In the first step of this pathway, H₂O₂ is reduced to water by ascorbate peroxidase (APX) using ascorbate as the electron donor. The oxidized ascorbate (monodehydroascorbate) is regenerated by monodehydroascorbate reductase (MDAR).^[2] However, monodehydroascorbate is a radical and if not rapidly reduced it disproportionates into ascorbate and dehydroascorbate. Dehydroascorbate is reduced to ascorbate by dehydroascorbate reductase at the expense of GSH, yielding oxidized glutathione (GSSG). Finally GSSG is reduced by glutathione reductase (GR) using NADPH as the electron donor. Thus ascorbate and glutathione are not consumed; the net electron flow is from NADPH to H₂O₂. The reduction of dehydroascorbate may be non-enzymatic or catalysed by proteins with dehydroascorbate reductase (DHAR) activity, such as glutathione S-transferase omega 1 or glutaredoxins.^[3]^[4]

In plants, the glutathione-ascorbate cycle operates in the cytosol, mitochondria, plastids and peroxisomes.^[5]^[6] Since glutathione, ascorbate and NADPH are present in high concentrations in plant cells it is assumed that the glutathione-ascorbate cycle plays a key role for H₂O₂ detoxification. Nevertheless, other enzymes (peroxidases) including peroxiredoxins and glutathione peroxidases, which use thioredoxins or glutaredoxins as reducing substrates, also contribute to H₂O₂ removal in plants.^[7]

See also

References

1. ^{{cite journal |vauthors=Noctor G, Foyer CH |title= ASCORBATE AND GLUTATHIONE: Keeping Active Oxygen Under Control |journal=Annu Rev Plant Physiol Plant Mol Biol|volume=49 |pages=249–279 |date=Jun 1998 |pmid=15012235 |doi=10.1146/annurev.arplant.49.1.249}}
2. ^{{cite journal |vauthors=Wells WW, Xu DP |title=Dehydroascorbate reduction |journal=J. Bioenerg. Biomembr. |volume=26 |issue=4 |pages=369–77 |date=August 1994 |pmid=7844111 |doi=10.1007/BF00762777}}
3. ^{{cite journal |vauthors=Whitbread AK, Masoumi A, Tetlow N, Schmuck E, Coggan M, Board PG |title=Characterization of the omega class of glutathione transferases |journal=Meth. Enzymol. |volume=401 |issue= |pages=78–99 |year=2005 |pmid=16399380 |doi=10.1016/S0076-6879(05)01005-0 }}
4. ^{{cite journal |vauthors=Rouhier N, Gelhaye E, Jacquot JP |title=Exploring the active site of plant glutaredoxin by site-directed mutagenesis |journal=FEBS Lett|volume=511 |issue=1–3 |pages=145–9 |year=2002 |pmid=11821065 | doi= 10.1016/S0014-5793(01)03302-6 }}
5. ^{{cite journal |author=Meyer A |title= The integration of glutathione homeostasis and redox signaling |journal= J Plant Physiol|volume=165 |pages=1390–403 |date=Sep 2009 |pmid=18171593 |doi=10.1016/j.jplph.2007.10.015 |issue=13 }}
6. ^{{cite journal |vauthors=Jimenez A, Hernandez JA, Pastori G, del Rio LA, Sevilla F |title= Role of the Ascorbate-Glutathione Cycle of Mitochondria and Peroxisomes in the Senescence of Pea Leaves |journal= Plant Physiol |volume=118|issue=4 |pages=1327–35 |date=Dec 1998 |pmid=9847106 |doi=10.1104/pp.118.4.1327 |pmc=34748}}
7. ^{{cite journal |vauthors=Rouhier N, Lemaire SD, Jacquot JP |title= The role of glutathione in photosynthetic organisms: emerging functions for glutaredoxins and glutathionylation |journal= Annu Rev Plant Biol |volume=59|issue= |pages=143–66 |year=2008 |pmid=18444899|doi=10.1146/annurev.arplant.59.032607.092811}}