In Section S4 of the ESI, we show that 3,594 reactions are catalysed by 3,079 enzymes, from which 424 enzymes catalyze more than one reaction. Thus, enzymes have the possibility to promiscuously catalyse non-native reactions. We made a strong assumption that all enzymes were promiscuous and assigned native enzymes to catalyse the predicted reactions with likelihoods by following the proposed transformer method, inspired from NLP, to translate between a reaction language to an enzyme language.