Glutaredoxins
(also known as Thioltransferase) are small
redox enzymes of approximately one hundred amino-acid residues that use
glutathione as a cofactor. In humans this oxidation repair enzyme is also known to participate in many cellular functions, including redox signaling and regulation of glucose metabolism.
Glutaredoxins are oxidized by substrates, and reduced non-enzymatically by glutathione. In contrast to
thioredoxins, which are reduced by
thioredoxin reductase, no oxidoreductase exists that specifically reduces glutaredoxins. Instead, glutaredoxins are reduced by the oxidation of glutathione. Reduced glutathione is then regenerated by
glutathione reductase. Together these components compose the glutathione system.
Like
thioredoxin, which functions in a similar way, glutaredoxin possesses an active centre disulfide bond.
It exists in either a reduced or an oxidized form where the two cysteine residues are linked in an intramolecular disulfide bond. Glutaredoxins function as electron carriers in the glutathione-dependent synthesis of
deoxyribonucleotides
A deoxyribonucleotide is a nucleotide that contains deoxyribose. They are the monomeric units of the informational biopolymer, deoxyribonucleic acid ( DNA). Each deoxyribonucleotide comprises three parts: a deoxyribose sugar ( monosaccharide), a n ...
by the enzyme
ribonucleotide reductase
Ribonucleotide reductase (RNR), also known as ribonucleoside diphosphate reductase (rNDP), is an enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides. It catalyzes this formation by removing the 2'-hydroxyl group of th ...
.
Moreover, GRX act in antioxidant defense by reducing
dehydroascorbate,
peroxiredoxins
Peroxiredoxins (Prxs, ; HGNC root symbol ''PRDX'') are a ubiquitous family of antioxidant enzymes that also control cytokine-induced peroxide levels and thereby mediate signal transduction in mammalian cells. The family members in humans are PRDX ...
, and methionine sulfoxide reductase. Beside their function in antioxidant defense, bacterial and plant GRX were shown to bind
iron-sulfur clusters and to deliver the cluster to enzymes on demand.
In viruses
Glutaredoxin has been sequenced in a variety of
viruses. On the basis of extensive sequence similarity, it has been proposed
that ''
Vaccinia virus'' protein O2L is, it seems, a glutaredoxin. ''
Bacteriophage T4'' thioredoxin seems to be evolution-related. In position 5 of the pattern T4, thioredoxin has Val instead of Pro.
In plants
Approximately 30 GRX isoforms are described in the model plant ''
Arabidopsis thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land.
A winter a ...
'' and 48 in Oryza sativa L. According to their redox-active centre, they are subgrouped in six classes of the CSY
/S, CGFS-, CC-type and 3 groups with additional domain of unknown function. The CC-type GRXs are only found in
higher plants. In Arabidopsis GRXs are involved in flower development and
Salicylic acid
Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substance ...
signalling.
Subfamilies
*Glutaredoxin subgroup
Human proteins containing this domain
GLRX;
GLRX2;
GLRX3
Glutaredoxin-3 is a protein that in humans is encoded by the ''GLRX3'' gene.
Interactions
GLRX3 has been shown to interact with PRKCQ
Protein kinase C theta (PKC-θ) is an enzyme that in humans is encoded by the ''PRKCQ'' gene. PKC-θ, a member ...
;
GLRX5;
PTGES2
Microsomal prostaglandin E synthase-2 (mPGES-2) or Prostaglandin E synthase 2 is an enzyme that in humans encoded by the ''PTGES2'' gene located on chromosome 9. The protein encoded by this gene is a membrane-associated prostaglandin E synthase, ...
References
External links
Enzyme database entry*
EC 1.20.4
Protein domains
Single-pass transmembrane proteins
Antioxidants
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