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 BBOV_I004500
Peroxiredoxin 1.11.1.15 BBOV_II004970
Peroxiredoxin 1.11.1.15 BBOV_IV005180
Peroxiredoxin 1.11.1.15 BBOV_IV010730
Superoxide dismutase (Fe) 1.15.1.1 BBOV_IV011480
Ribonucleotide di-P reductase 1.17.4.1 BBOV_I004870
Ribonucleotide di-P reductase 1.17.4.1 BBOV_IV006460
Ribonucleotide di-P reductase 1.17.4.1 BBOV_IV010610
Thioredoxin reductase 1.8.1.9 BBOV_I002190
Glutathione S-transferase 2.5.1.18 BBOV_IV006320
Glutathione S-transferase 2.5.1.18 BBOV_IV006330
gamma-Glutamylcysteine synthetase 6.3.2.2 BBOV_I002580
Glutathione synthase 6.3.2.3 BBOV_IV004820
Thioredoxin none BBOV_II003650
Glutaredoxin none BBOV_II007360
Glutaredoxin none BBOV_II007430
Thioredxin none BBOV_III004570
Thioredoxin none BBOV_III011040
Thioredxin none BBOV_IV000170
Thioredoxin none BBOV_IV002330
Thioredoxin none BBOV_IV003150
Glutaredoxin none BBOV_IV004320
Thioredxin none BBOV_IV006740
Thioredxin none BBOV_IV007040
Thioredoxin none BBOV_IV011170