Figure 4. Hypothetical pathways for reactive oxygen species (ROS) detoxification.

Pathways evidenced in both ciliates (white background) or only in Strombidium rassoulzadegani (yellow background) are shown. In red, ROS (O₂ ^-  =  superoxide radical; H₂O₂  =  hydrogen peroxide); in dark blue, antioxidant enzymes (SOD  =  superoxide dismutase; Cat  =  catalase; APX  =  ascorbate peroxidase; GPX  =  glutathione peroxidase; TPX  =  thioredoxin peroxidase); in light blue, enzymes involved in metabolism of non-enzymatic antioxidants (Nec3  =  bifunctional monodehydroascorbate reductase/carbonic anhydrase nectarin-3-like; TRed  =  thioredoxin reductase; GRed  =  glutathione reductase; GSyn  =  GSH synthetase; GCLig  =  Glutamate-cysteine ligase); in green, non-enzymatic antioxidants (AsA  =  ascorbic acid; GSH  =  glutathione; Trx  =  thioredoxin). MDAs  =  monodehydroascorbate; GSSG  =  glutathione disulfide; TrxS₂  =  thioredoxin disulfide; NAD(P)⁺  =  nicotinamide adenine dinucleotide (phosphate). Based on literature [61], [63], [75].