Pentose phosphate cycle
Pentose phosphate cycle, also called as phosphogluconate pathway and hexose monophosphate shunt is important for Neospora caninum and organisms in general for three functions.
- To recycle the reducing equivalents such as NADPH for other reductive metabolic pathways (e.g. fatty acid biosynthesis, isoprenoids biosynthesis, nitrogen metabolism, shikimate biosynthesis etc).
- To produce ribose-5-phosphate for synthesis of PRPP, an essential substrate in pyrimidine biosynthesis.
- To synthesise erythrose-4-phosphate an essential substrate in shikimate biosynthesis. The end product of this pathway, chorismate is important for folate biosynthesis. It is also important for the biosynthesis of aromatic amino acids, a capability which is absent in all apicomplexans.
The pathway can be divided into two phases, oxidative phase and non-oxidative phase. The first three enzymes of the pathway form the oxidative phase, where NADPH is generated and ribulose-5-phosphate is produced. All the downstream enzymes form part of second non-oxidative phase, where ribose-5-phpshate and ultimately PRPP and erythrose-4-phosphate are generated. Pentose phosphate cycle is present in Plasmodium falciparum, Toxoplasma gondii and N. caninum. The pathway here is same as the pathway for T. gondii.
Enzyme | EC Number | Gene id |
---|---|---|
6-phosphogluconate dehydrogenase | 1.1.1.44 | NCLIV_017630 |
6-phosphogluconate dehydrogenase | 1.1.1.44 | NCLIV_060600 |
Glucose-6P dehydrogenase | 1.1.1.49 | NCLIV_000940 |
Glucose-6P dehydrogenase | 1.1.1.49 | NCLIV_068740 |
Bifunctional glucose-6P dehydrogenase/6-phosphoglucolactonase | 1.1.1.49; 3.1.1.31 | NCLIV_067180 |
Transketolase | 2.2.1.1 | NCLIV_011210 |
Transaldolase | 2.2.1.2 | NCLIV_030290 |
Ribokinase | 2.7.1.15 | NCLIV_001280 |
Ribosephosphate pyrophosphokinase | 2.7.6.1 | NCLIV_012230 |
Ribosephosphate pyrophosphokinase | 2.7.6.1 | NCLIV_015140 |
ADP-ribose diphosphatase | 3.6.1.13 | NCLIV_023800 |
Deoxyribose-phosphate aldolase | 4.1.2.4 | NCLIV_010810 |
Deoxyribose-phosphate aldolase | 4.1.2.4 | NCLIV_036120 |
Ribulose-phosphate 3-epimerase | 5.1.3.1 | NCLIV_065340 |
Ribosephosphate isomerase | 5.3.1.6 | NCLIV_015970 |
Phosphoglucomutase | 5.4.2.2 | NCLIV_010960 |
Phosphoglucomutase | 5.4.2.2 | NCLIV_014450 |
Sources and fates of metabolites
Substrate | Source pathways | Product | Fate pathways |
---|---|---|---|
D-Glucose-6P | Glycolysis | D-Erythrose-4P | Shikimate biosynthesis |
D-Glyceraldehyde-3P | Glycolysis | D-Glyceraldehyde-3P | Glycolysis |
D-Fructose-6P | Glycolysis | D-Fructose-6P | Glycolysis |
D-Ribose-1P | Purine metabolism | PRPP | Purine metabolism, Pyrimidine metabolism, Nicotinate and nicotinamide metabolism |
- Log in to post comments