Proline metabolism

Proline is a non essential amino acid which is de novo synthesised from glutamate (glutamate metabolism pathway) in Toxoplasma gondii [1]. This pathway shows the enzymes that catalyse the conversion of proline into 4-hydroxy-L-proline and ornithine. The absence of the enzyme arginase (converts arginine into ornithine) in T. gondii has led to the shortening of arginine and proline metabolism pathway in MPMP to proline metabolism pathway here. Although the activities of enzymes catalysing conversion of arginine to carbamoyl phosphate and ornithine were experimentally demonstrated [2], the genes for those enzymes were not identified (refer to methionine metabolism for more details).

 

Enzyme EC Number Gene id Protein localisation Localisation data source
Proline hydroxylase 1.14.11.2 TGME49_221270    
Proline hydroxylase 1.14.11.2 TGME49_290920 Nucleus Previous publication
Pyrroline-5-carboxylate reductase 1.5.1.2 TGME49_236070 Extracellular? Previous publication
Pyrroline-5-carboxylate reductase 1.5.1.2 TGME49_271610 Apicoplast Previous publication
Proline dehydrogenase 1.5.99.8 TGME49_202340    
Ornithine aminotransferase 2.6.1.13 TGME49_269110    
Pro-tRNA ligase 6.1.1.15 TGME49_219850 Cytosol Apiloc; Previous publication

 

  List of genes annotated as tRNA-Pro in Toxoplasma gondii genome

 

TGME49_024500 TGME49_025024 TGME49_032070 TGME49_059938
TGME49_069790 TGME49_070180 TGME49_085960 TGME49_086265
TGME49_097990 TGME49_098000 TGME49_099825 TGME49_100631
TGME49_121320      

 

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Sources and fates of metabolites

 

Substrate Source pathways Product Fate pathways
Proline Glutamate metabolism 4-hydroxy-L-proline ?
2-oxoglutarate Pyruvate metabolism, Tricarboxylic acid (TCA) cycle Succinate Tricarboxylic acid (TCA) cycle