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 Chro.40088
Histone-lysine N-methyltransferase 2.1.1.43 Chro.10248
Histone-lysine N-methyltransferase 2.1.1.43 Chro.40051
Histone-lysine N-methyltransferase 2.1.1.43 Chro.40234
Histone-lysine N-methyltransferase 2.1.1.43 Chro.70122
Acylaminoacyl-peptidase 3.4.19.1 Chro.50405
Lysine-tRNA ligase 6.1.1.6 Chro.40267

 

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

 

Chro.trn003 Chro.trn010 Chro.trn034

 

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Sources and fates of metabolic pathways

 

Substrate Source pathways Product Fate pathways
Lysine Host Saccharopine Host?