Afterwards, for each analogue reaction 𝑗 ∈ 𝐽 under the level of each detected similar compound 𝑠 " ∈ 𝑆, the objective is to predict reaction from an unknown reactant 𝑞 ",$ to the target product 𝑡 based on the functional group transformation at the reaction centre of an analogue reaction 𝑗 from the reactant 𝑟 ",$ to the similar compound 𝑠 " (or in a reversed direction, given that all enzymatic reactions are assumed reversible).