From: A genome-scale metabolic flux model of Escherichia coli K–12 derived from the EcoCyc database
Nitrogen source | HT | Sim | Comments |
---|---|---|---|
Guanine | + | – | Guanine is not used as a nitrogen source by E. coli[173, 174] in vivo, and its degradation does not proceed past allantoin. EcoCyc–18.0–GEM is able to use guanine as a source of ammonia by means of glucose deamination and immediate excretion of xanthine or urate. |
5-aminopentanoate | + | – | Routes of uptake and catabolism are unknown for 5-aminopentanoate and glucuronamide. |
Glucuronamide | + | – | |
Ethanolamine | – | + | E. coli requires a source of cob(I)alamin for catabolism of ethanolamine by the adenosylcobalamin-dependent ethanolamine ammonia-lyase [169–172]. MetaFlux does not currently model enzyme cofactor requirements. |
Allantoin | – | + | Anaerobic conditions are required for E. coli to use allantoin as a nitrogen source [175]. MetaFlux does not currently model gene regulation. |
Nitrate | – | + | Nitrate and nitrite pass through nitrate and nitrite reductase pathways, which operate only under anaerobic |
Nitrite | – | + | conditions and do not function in an assimilatory fashion in E. coli[176–178]. |
L-tyrosine | – | + | E. coli lacks a catabolic aromatic amino acid transaminase, preventing the utilization of L-tyrosine as a nitrogen source; the path of utilization in EcoCyc–18.0–GEM involves the tyrosine lyase used in thiazole biosynthesis followed by spontaneous dissociation of 2-iminoacetate to glyoxylate and ammonium, and is not biologically realistic due to the production of large quantities of the dead-end metabolites 5’-deoxyadenosine and p-cresol. |