An example of subpools of a metabolite pool. Phosphoenolpyruvate (PEP) is produced by two different reactions (ρi and ρj), either from Oxaloacetate (OAA) or from glyceraldehyde 3-phosphate (GA3P). Thus, PEP has two in flow subpools, PEP from OAA and PEP from GA3P (grey boxes) that are mixed in the common PEP pool (at the bottom).
Rantanen et al. BMC Bioinformatics 2008 9:266 doi:10.1186/1471-2105-9-266