REDUCTANT RECOVERY SYSTEMS
Living things possess a recovery system to rescue oxidized sulfur compounds. It operates through donation of hydrogen atoms to these compounds and thereby restores their original condition as thiols. [59a,59b]

2 [H] + (GSSG) -> 2(GSH) This system is known as the hexose monophophate shunt. [59c,59d] A key player in this system is the enzyme glucose-6-phosphate-dehydrogenase (G6PDH). Patients with a genetic defect of G6PDH, known as glucose-6-phosphate-dehydrogenase deficiency disease, are especially sensitive to oxidants and to prooxidant drugs. However, this genetic disease has a benefit in that such individuals are naturally resistant to malaria. They can still catch malaria, but it is much less severe in them, since they permanently lack the enzyme necessary to assist the parasite in reactivating glutathione and other oxidized thiols. [60a-60h] Chlorine dioxide (ClO2) has been shown to oxidize and denature G6PDH by reaction with tyrosine and tryptophan residues inside the enzyme. [61a] Furthermore, G6PDH is sensitive to inhibition by sodium chlorate (NaClO3), another member of the chlorine oxide family of compounds. [61b,61c,61d] Sodium chlorate (NaClO3) is a trace ingredient present in the acicified sodium chlorite antimalarial solution. Some sodium chlorate (NaClO3) should also be produced in vivo by a slow reaction of chlorine dioxide (ClO2) with water under alkaline conditions [61e]. 2(ClO2) + 2(OH-) -> (ClO2-) + (ClO3-) + H2O

The Plasmodia may attempt to restore any thiols (RSH) lost to oxidation. However, this becomes more difficult as G6PDH is inhibited by chlorine dioxide (ClO2) or by chlorate (ClO3-).