Alanine metabolism

The single step synthesis of alanine from pyruvate is unique to Coccidians such as Toxoplasma and Neospora among the phylum of Apicomplexa. This is absent in other groups such as Plasmodium, Theileria and Cryptosporidium species, which utilise alanine from host [1]. Alanine dehydrogenase and alanine transaminase are the enzymes which catalyse this one step conversion. Alanine racemase, a pyridoxal phosphate dependent enzyme which catalyses isomerisation of L-alanine to D-alanine is present in Plasmodium falciparum, Neospora caninum and Toxoplasma gondii genomes and annotated to pyridoxal phosphate metabolism pathway in MPMP as an example of enzyme which requires pyridoxal phosphate as cofactor for its function. The only difference between T. gondii and N. caninum in this pathway is the copy number variation of alanine dehydrogenase enzyme (2 in T. gondii and 3 in N. caninum).

 

Enzyme EC Number Gene id
Alanine dehydrogenase 1.4.1.1 NCLIV_021470
Alanine dehydrogenase 1.4.1.1 NCLIV_021480
Alanine dehydrogenase 1.4.1.1 NCLIV_058000
Alanine transaminase 2.6.1.2 NCLIV_024040
Alanine racemase 5.1.1.1 NCLIV_010840
Ala-tRNA ligase 6.1.1.7 NCLIV_061050

 

List of genes annotated as tRNA-Ala in N. Caninum genome

 

NC_LIV_tRNA_020005 NC_LIV_tRNA_020006 NC_LIV_tRNA_030004 NC_LIV_tRNA_040003
NC_LIV_tRNA_040004 NC_LIV_tRNA_060006 NC_LIV_tRNA_140002 NC_LIV_tRNA_140017
NC_LIV_tRNA_140020      

 

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Sources and fates of metabolites

 

Substrate Source pathways Product Fate pathways
Pyruvate Glycolysis D-alanine ?
Glutamate Glutamate metabolism 2-oxglutarate Tricarboxylic acid (TCA) cycle, Glutamate metabolism