Glycine, serine and cysteine metabolism
Toxoplasma gondii possesses the ability to synthesise glycine, serine and cysteine. Toxoplasma can synthesise serine with glycerate/glycerate-3-phosphate as the substrate. The Toxoplasma genome has the genes for the enzymes glycerate kinase, phosphoglycerate dehydrogenase, phosphoserine transaminase and phosphoserine phosphatase which lead to the de novo biosynthesis of serine. This is consistent with the previous observation that Toxoplasma can synthesise serine, whereas Plasmodium has an auxotrophic requirement for serine from hosts [1]. The presence of genes for the enzymes cystathionine beta-synthase (4.2.1.22) and cystathionine gamma-lyase (4.4.1.1) suggests that it can inter-convert serine into cysteine as in humans and in other animals. However, it has been suggested that Toxoplasma possesses an auxotrophic requirement for cysteine before [1]. These observations have led to the extension of glycine and serine metabolism pathway in MPMP into glycine, serine and cysteine metabolism pathway for Toxoplasma.
Enzyme | EC Number | Gene id | Protein localisation | Localisation data source |
---|---|---|---|---|
Glycerate dehydrogenase | 1.1.1.29 | TGME49_214760 | Extracellular? | Previous publication |
Phosphoglycerate dehydrogenase | 1.1.1.95 | TGME49_239820 | Cytosol | Previous publication |
Glycine dehydrogenase | 1.4.4.2 | Missing in annotation | ||
Dihydrolipoyl dehydrogenase | 1.8.1.4 | TGME49_206470 | Mitochondrion | Apiloc; Previous publication |
Dihydrolipoyl dehydrogenase | 1.8.1.4 | TGME49_305980 | Apicoplast | Apiloc; Previous publication; Orthology transformation from P. falciparum |
Serine hydroxymethyltransferase | 2.1.2.1 | TGME49_234190 | Cytoskeleton | Previous publication |
Aminomethyltransferase | 2.1.2.10 | TGME49_237470 | Mitochondrion | Previous publication |
Aminomethyltransferase | 2.1.2.10 | TGME49_283820 | ||
5-aminolevulinate synthase | 2.3.1.37 | TGME49_258690 | ||
Asparate transaminase | 2.6.1.1 | TGME49_248600 | Cytosol | Previous publication |
Serine/pyruvate transaminase | 2.6.1.51 | TGME49_239530 | Cytosol | Previous publication |
Phosphoserine transaminase | 2.6.1.52 | TGME49_218780 | Cytosol | Previous publication |
Glycerate kinase | 2.7.1.31 | TGME49_244150 | Nucleus | Previous publication |
3-mercaptopyruvate sulfurtransferase | 2.8.1.2 | TGME49_305910 | Extracellular? | Previous publication |
Phosphoserine phosphatase | 3.1.3.3 | TGME49_222900 | ||
Cystathionine beta-synthase | 4.2.1.22 | TGME49_259180 | ||
Cystathionine gamma-lyase | 4.4.1.1 | TGME49_312930 | ||
Serine-tRNA ligase | 6.1.1.11 | TGME49_251690 | Apicoplast | Previous publication |
Serine-tRNA ligase | 6.1.1.11 | TGME49_271625 | Apicoplast | Apiloc |
Glycine-tRNA ligase | 6.1.1.14 | TGME49_254200 | ||
Glycine-tRNA ligase | 6.1.1.14 | TGME49_256990 | Apicoplast | Previous publication |
Cysteine-tRNA ligase | 6.1.1.16 | TGME49_299810 | Apicoplast | Apiloc; Previous publication |
List of genes annotated as tRNA-Gly in T. gondii genome
TGME49_002660 | TGME49_002670 | TGME49_028075 | TGME49_046680 |
TGME49_055230 | TGME49_057386 | TGME49_077960 | TGME49_088755 |
TGME49_088760 | TGME49_088765 | TGME49_088770 | TGME49_094100 |
TGME49_101999 |
List of genes annotated as tRNA-Ser in T. gondii genome
TGME49_007365 | TGME49_007380 | TGME49_007810 | TGME49_008480 |
TGME49_020620 | TGME49_054100 | TGME49_075340 | TGME49_088980 |
TGME49_100634 | TGME49_101997 | TGME49_110875 | TGME49_110880 |
TGME49_119330 |
List of genes annotated as tRNA-Cys in T. gondii genome
TGME49_057383 | TGME49_082100 | TGME49_082110 | TGME49_082120 |
TGME49_100637 | TGME49_105505 |
Sources and fates of metabolites
Substrate | Source pathways | Product | Fate pathways |
---|---|---|---|
3-P-D-glycerate | Glycolysis | ||
L-Glutamate | Glutamate metabolism | 2-oxoglutarate | Tricarboxylic acid (TCA) cycle, Glutamate metabolism |
2-oxoglutarate | Pyruvate metabolism, Tricarboxylic acid (TCA) cycle | L-Glutamate | Glutamate metabolism |
Alanine | Alanine metabolism | Pyruvate | Glycolysis, Pyruvate metabolism, Alanine metabolism |
Tetrahydrofolate | Folate biosynthesis | 5,10-methylene tetrahydrofolate | Folate biosynthesis |
Succinyl-CoA | Tricarboxylic acid (TCA) cycle | 5-aminolevulinate | Porphyrin metabolism |
L-homocysteine | Methionine metabolism | 2-oxobutanoate | Host? |
Sulfite | Host? | Thiosulfate | Host? |
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