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. parvum gene models.

 

Enzyme EC Number Gene id
Glutamate-5-semialdehyde dehydrogenase 1.2.1.41 cgd7_4940
Pyrroline-5-carboxylate reductase 1.5.1.2 cgd6_3720
Glutaminyl-peptide cyclotransferase 2.3.2.5 cgd1_730
Hexosephosphate aminotransferase 2.6.1.16 cgd1_3730
Glutamate 5-kinase 2.7.2.11 cgd2_2300
Glutamyl-tRNA synthetase 6.1.1.17 cgd8_790
Glutaminyl-tRNA synthetase 6.1.1.18 cgd1_2130
L-glutamate ammonia ligase 6.3.1.2 cgd6_4570

 

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

 

cgd3_605 cgd3_865

 

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

 

cgd6_3565 cgd8_4976

 

Open in a new window

 

 

Sources and fates of metabolic pathways

 

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