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 Chro.40088
Histone-lysine N-methyltransferase Chro.10248
Histone-lysine N-methyltransferase Chro.40051
Histone-lysine N-methyltransferase Chro.40234
Histone-lysine N-methyltransferase Chro.70122
Acylaminoacyl-peptidase Chro.50405
Lysine-tRNA ligase 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?