Table 3  Protective enzymes that can be up-regulated in response to ROS exposure
The thioredoxin system
 ThioredoxinTRX1, TRX2CytDisulfide oxidoreductase activity
TRX3MitMitochondrial disulphide oxidoreductase activity
 Thioredoxin reductaseTRR1CytReduces oxidized thioredoxins (Trx1, Trx2)
TRR2MitReduces oxidized thioredoxin (Trx3)
 PeroxiredoxinTSA1, TSA2Cyt2-Cys Prx, thioredoxin peroxidase and chaperone activity
AHP1Cyt2-Cys Prx, thioredoxin peroxidase particularly with alkyl hydroperoxides
DOT5NucNuclear 2-Cys Prx, functions in telomeric silencing
PRX1MitMitochondrial 1-Cys Prx, thioredoxin peroxidase activity
The glutathione system
 GSH synthesisGSH1, GSH2CytCatalyze two ATP-dependent steps in GSH biosynthesis
 Glutathione reductaseGLR1Cyt/MitRecycles oxidized GSSG to reduced GSH, co-localizes to Cyt and Mit
 Glutathione transferaseGTT1ERCatalyze the conjugation of GSH to various electrophiles
GTO1PerOmega class glutathione transferase
GTO2, GTO3CytOmega class glutathione transferase
 Glutathione peroxidaseGPX1, GPX2CytPhospholipid hydroperoxide glutathione peroxidase
GPX3CytPhospholipid hydroperoxide glutathione peroxidase, Yap1 signal transducer
 GlutaredoxinGRX1CytGlutathione disulfide oxidoreductase activity
 GRX2Cyt/MitGlutathione disulfide oxidoreductase activity, colocalizes to Cyt and Mit
GRX3, GRX4NucMonothiol glutaredoxin
GRX5MitMonothiol glutaredoxin, synthesis/assembly of iron-sulfur centers
GRX6, GRX7GolCis-Golgi localized monothiol glutaredoxins
GRX8CytGlutathione disulfide oxidoreductase activity
 Superoxide dismutaseSOD1Cyt/NucCatalyze the dismutation of superoxide into oxygen and hydrogen peroxide
 CatalaseCTT1CytCatalyze the reduction of hydrogen peroxide to water and oxygen
 Methionine sulphoxideMXR1 (MSRA)CytCatalyze thiol-dependent reduction of methionine (S)-sulfoxide
 ReductaseMXR2 (MSRB)MitCatalyze thiol-dependent reduction of methionine (R)-sulfoxide
fRMsr (YKL069W)CytCatalyze thiol-dependent reduction of free Met-R-SO
 ErythroascorbateALO1MitD-arabinono-1,4-lactone oxidase, final step of erythroascorbate synthesis