Glutamate metabolism

Glutamate and glutamine are non-essential amino acids in both Toxoplasma gondii and Plasmodium falciparum as in humans, whereas glutamate is an essential amino acid utilised from host in Cryptosporidium species. This is because the 2-oxoglutarate, the TCA cycle intermediate required for glutamate synthesis cannot be synthesised as the TCA cycle enzymes are missing in most of Cryptosporidium species. Although Cryptosporidium muris possess TCA cycle, the enzymes glutamate dehydrogenase and aspartate transaminase involved in glutamate synthesis are absent in the Cryptosporidum species. The ecological niches of gastric glands of stomach for C. muris and epithelial cells of small intestine for Cryptosporidium parvum and Cryptosporidium hominis provide them with the advantage of their ability to fulfil amino acid requirements from the host. These species possess the enzyme, glutamate-ammonia ligase and therefore can de novo synthesise glutamine. Cryptosporidia possess the capability to de novo synthesise proline from glutamate as in humans and in T. gondii [1]. The genes for all the enzymes involved in this process are present in C. hominis gene models.


Enzyme EC Number Gene id
Glutamate-5-semialdehyde dehydrogenase Chro.70551
Pyrroline-5-carboxylate reductase Chro.60426
Glutaminyl-peptide cyclotransferase Chro.10089
Hexosephosphate aminotransferase Chro.10420
Glutamate 5-kinase Chro.20246
Glutamyl-tRNA synthetase Chro.80098
Glutaminyl-tRNA synthetase Chro.10244
L-glutamate ammonia ligase Chro.60524


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


Chro.trn024 Chro.trn029


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


Chro.trn005 Chro.trn012


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Sources and fates of metabolic pathways


Substrate Source pathways Product Fate pathways
D-Fructose-6P Glycolysis Glucosamine-6P Aminosugars metabolism
    L-Proline Proline metabolism