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 1.2.1.41 Chro.70551
Pyrroline-5-carboxylate reductase 1.5.1.2 Chro.60426
Glutaminyl-peptide cyclotransferase 2.3.2.5 Chro.10089
Hexosephosphate aminotransferase 2.6.1.16 Chro.10420
Glutamate 5-kinase 2.7.2.11 Chro.20246
Glutamyl-tRNA synthetase 6.1.1.17 Chro.80098
Glutaminyl-tRNA synthetase 6.1.1.18 Chro.10244
L-glutamate ammonia ligase 6.3.1.2 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