Operator vector of enzyme reaction and a sequence of applications of operator vectors. (A) An operator vector expresses the change in chemical structure before and after the reaction, which is computed as the difference between the product compound vector and the substrate compound vector. (B) An application of an enzyme reaction to a compound can be done simply by "addition" of the operator vector to the compound vector. Therefore, a reaction pathway is represented by a sequence of additions of operator vectors.
Nakamura et al. BMC Bioinformatics 2012 13(Suppl 17):S8 doi:10.1186/1471-2105-13-S17-S8