Lysine metabolism

Lysine is an essential amino acid in most Apicomplexa species as in humans and need to be utilised from host. The exception to this is the cyst forming Coccidians such as Toxoplasma gondii and Neospora caninum. The Cryptosporidia species possess the gene for the enzyme saccharopine dehydrogenase which converts lysine to saccharopine which can be degraded to 2-oxodipate in the host. The other enzymes involved in lysine degradation in Plasmodia and cyst forming Coccidia are absent in Cryptosporidia. This pathway also includes large number of genes coding histone-lysine N-methyltransferase which catalyses protein methylation.

 

Enzyme EC Number Gene id
Saccharopine dehydrogenase 1.5.1.7 cgd4_700
Histone-lysine N-methyltransferase 2.1.1.43 cgd1_2170
Histone-lysine N-methyltransferase 2.1.1.43 cgd4_2090
Histone-lysine N-methyltransferase 2.1.1.43 cgd4_370
Histone-lysine N-methyltransferase 2.1.1.43 cgd7_980
Acylaminoacyl-peptidase 3.4.19.1 cgd5_4370
Lysine-tRNA ligase 6.1.1.6 cgd4_2370

 

List of genes annotated as tRNA-Lys in C. parvum genome

 

cgd1_905 cgd8_1575

 

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Sources and fates of metabolic pathways

 

Substrate Source pathways Product Fate pathways
Lysine Host Saccharopine Host?