Redox metabolism

Redox metabolism is an important metabolic pathway in all apicomplexans. This pathway shows the series of oxidation/reduction activities involved in removal of oxidative radicals such as superoxide anions, hydrogen peroxide and other toxic nucleophiles produced from different metabolic reactions. These reactive oxygen species cause oxidative damage to DNA, lipids and proteins. There are several antioxidant systems present in cells to protect them from these damages. This includes enzymes such as superoxide dismutase which reduces superoxide anion to H2O2 and catalase which reduces H2O2 to water and oxygen. The enzyme peroxiredoxin also reduces H2O2. The oxidised peroxiredoxin can be reduced back by thiols such as glutathione and thioredoxin. The glutathione system consists of glutathione and the enzymes glutathione peroxidase, glutathione reductase and glutathione S-transferase [1]. Glutathione is a tripeptide of glutamine-cysteine-glycine and synthesised de novo in two reactions steps. This glutathione synthesis is also included in this pathway. Glutathione peroxidase and glutathione S-transferase catalyse reduction of oxidative radicals by oxidising glutathione. Glutathione can be reduced back by glutathione reductase [1]. Although glutathione synthase and glutathione S-transferase are present in Piroplasma species, glutathione peroxidase and glutathione reductase are absent in the gene models. Another redox protein thioredoxin is important in reduction of ribonucleotides to deoxyribonucleotides and its partner thioredoxin reductase catalyses reduction of oxidised thioredoxin using NADPH as electron donor. Catalase is also absent in Piroplasma species.

 

Enzyme EC Number Gene id
Peroxiredoxin 1.11.1.15 TP01_0177
Peroxiredoxin 1.11.1.15 TP01_0224
Peroxiredoxin 1.11.1.15 TP01_0735
Peroxiredoxin 1.11.1.15 TP04_0036
Peroxiredoxin 1.11.1.15 TP04_0177
Superoxide dismutase (Fe) 1.15.1.1 TP01_1156
Superoxide dismutase (Fe) 1.15.1.1 TP04_0025
Ribonucleotide di-P reductase 1.17.4.1 TP01_0725
Ribonucleotide di-P reductase 1.17.4.1 TP01_1196
Ribonucleotide di-P reductase 1.17.4.1 TP03_0528
Thioredoxin reductase 1.8.1.9 TP03_0110
Glutathione S-transferase 2.5.1.18 TP01_0445
gamma-Glutamylcysteine synthetase 6.3.2.2 TP03_0084
Glutathione synthase 6.3.2.3 TP01_0264
Glutathione synthase 6.3.2.3 TP01_0265
Glutaredoxin none TP01_0320
Thioredoxin none TP01_0471
Thioredoxin none TP01_0642
Glutaredoxin none TP02_0196
Thioredxin none TP02_0813
Thioredxin none TP02_0945
Thioredxin none TP03_0204
Thioredoxin none TP03_0419
Thioredxin none TP04_0061
Thioredoxin none TP04_0217