KEGG functional modules.A: A pathway module. The module M00009 comprising 8 reactions is defined for the citrate cycle (TCA cycle) core module and represented as a Boolean algebra-like equation of KO identifiers or K numbers for computational applications. The relationship between this module and the corresponding KEGG pathway map is also shown by indicating corresponding K number sets in the module and EC numbers in the pathway map using the same index. In each K number set, vertically connected K numbers indicate a complex and therefore represent “And” or “+” in the Boolean algebra-like equation, whereas horizontally located K numbers indicate alternatives and represent “Or” or “,” in the equation. B: A structural complex module. The structural complex module M00163 comprising 12 (cyanobacteria) or 14 (plant) components is defined for the type I photosystem. The Boolean algebra-like equation and the corresponding KEGG pathway map are also shown. The KEGG pathway map shows the Thermosynechococcus elongatus (cyanobacteria) photosystem. Green and purple boxes indicate plant and cyanobacteria components, respectively.
Takami et al. BMC Genomics 2012 13:699 doi:10.1186/1471-2164-13-699