Proline metabolism

Proline is a non essential amino acid which is de novo synthesised from glutamate (glutamate metabolism pathway) in Neospora caninum and Toxoplasma gondii. This pathway shows the enzymes which 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 and N. caninum has led to the shortening of arginine and proline metabolism pathway in MPMP to proline metabolism pathway for T. gondii and N. caninum here. Although the activities of enzymes catalysing conversion of arginine to carbamoyl phosphate and ornithine were experimentally demonstrated in T. gondii [1], the genes for those enzymes were not identified in either T. gondii or N. caninum genomes (refer to methionine metabolism for more details).

 

Enzyme EC Number Gene id
Proline hydroxylase 1.14.11.2 NCLIV_004830
Proline hydroxylase 1.14.11.2 NCLIV_042790
Pyrroline-5-carboxylate reductase 1.5.1.2 NCLIV_035400
Pyrroline-5-carboxylate reductase 1.5.1.2 NCLIV_050390
proline dehydrogenase 1.5.99.8 NCLIV_022590
Ornithine aminotransferase 2.6.1.13 NCLIV_037280
Pro-tRNA ligase 6.1.1.15 NCLIV_060760

 

List of genes annotated as tRNA-Pro in N. caninum genome

 

NC_LIV_tRNA_020011 NC_LIV_tRNA_030005 NC_LIV_tRNA_030006 NC_LIV_tRNA_060004
NC_LIV_tRNA_060005 NC_LIV_tRNA_090003 NC_LIV_tRNA_100003 NC_LIV_tRNA_100011
NC_LIV_tRNA_100015 NC_LIV_tRNA_120001 NC_LIV_tRNA_120002 NC_LIV_tRNA_140001

 

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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