Glycine, serine and cysteine metabolism
The Coccidians Toxoplasma gondii and Neospora caninum possess the ability to synthesise glycine, serine and cysteine. Toxoplasma and Neospora can synthesise serine with glycerate/glycerate-3-phosphate as the substrate. The Toxoplasma and Neospora genomes have 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) in T. gondii and N. caninum suggests that it can inter-convert serine into cysteine as in humans and in other animals. But, it has been suggested that Toxoplasma possesses an auxotrophic requirement for cysteine before [1]. These have led to the extension of glycine and serine metabolism pathway in MPMP into glycine, serine and cysteine metabolism pathway for Toxoplasma and Neospora here.
Enzyme | EC Number | Gene id |
---|---|---|
Glycerate dehydrogenase | 1.1.1.29 | NCLIV_051810 |
Phosphoglycerate dehydrogenase | 1.1.1.95 | NCLIV_016450 |
Glycine dehydrogenase | 1.4.4.2 | Missing in annotation |
Dihydrolipoyl dehydrogenase | 1.8.1.4 | NCLIV_044200 |
Dihydrolipoyl dehydrogenase | 1.8.1.4 | NCLIV_070190 |
Serine hydroxymethyltransferase | 2.1.2.1 | NCLIV_049400 |
Aminomethyltransferase | 2.1.2.10 | NCLIV_028840 |
Aminomethyltransferase | 2.1.2.10 | NCLIV_051210 |
5-aminolevulinate synthase | 2.3.1.37 | NCLIV_027820 |
Asparate transaminase | 2.6.1.1 | NCLIV_064760 |
Serine/pyruvate transaminase | 2.6.1.51 | NCLIV_016150 |
Phosphoserine transaminase | 2.6.1.52 | NCLIV_061600 |
Glycerate kinase | 2.7.1.31 | NCLIV_018750 |
3-mercaptopyruvate sulfurtransferase | 2.8.1.2 | NCLIV_070240 |
Phosphoserine phosphatase | 3.1.3.3 | NCLIV_005930 |
Cystathionine beta-synthase | 4.2.1.22 | NCLIV_027350 |
Cystathionine gamma-lyase | 4.4.1.1 | NCLIV_056280 |
Serine-tRNA ligase | 6.1.1.11 | NCLIV_035390 |
Serine-tRNA ligase | 6.1.1.11 | NCLIV_066770 |
Glycine-tRNA ligase | 6.1.1.14 | NCLIV_008470 |
Glycine-tRNA ligase | 6.1.1.14 | NCLIV_029970 |
Cysteine-tRNA ligase | 6.1.1.16 | NCLIV_060470 |
List of genes annotated as tRNA-Gly in N. caninum genome
NC_LIV_tRNA_010006 | NC_LIV_tRNA_010008 | NC_LIV_tRNA_010009 | NC_LIV_tRNA_080003 |
NC_LIV_tRNA_080004 | NC_LIV_tRNA_090007 | NC_LIV_tRNA_090011 | NC_LIV_tRNA_110002 |
NC_LIV_tRNA_140008 | NC_LIV_tRNA_140016 |
List of genes annotated as tRNA-Ser in N. caninum genome
NC_LIV_tRNA_020003 | NC_LIV_tRNA_020004 | NC_LIV_tRNA_020007 | |
NC_LIV_tRNA_040002 | NC_LIV_tRNA_040007 | NC_LIV_tRNA_050001 | NC_LIV_tRNA_060003 |
NC_LIV_tRNA_110003 | NC_LIV_tRNA_120012 | NC_LIV_tRNA_130005 |
List of genes annotated as tRNA-Cys in N. caninum genome
NC_LIV_tRNA_080007 | NC_LIV_tRNA_090008 | NC_LIV_tRNA_090009 | NC_LIV_tRNA_110012 |
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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