While RebH acts on free L-tryptophan (i.e. "free-floating"), MibH recognizes tryptophan only in the context of a peptide backbone where thioether macrocycles are already present. As a consequence thereof, the reaction SMARTS representing the RebH halogenation encompasses only the L-tryptophan/7-chloro-L-tryptophan substrate/product pair (Figure ). On the contrary, the reaction encoded by MibH would require the complete deschloro-NAI-107/NAI-107 reaction pair represented as reaction SMARTS (Figure ). Hereby, the introduced reaction (the chlorination) is relatively trivial, but the substrate context is significantly different. Therefore, reaction SMARTS harbor the potential to represent both generic and specific reactions with large flexibility in terms of the location and type of introduced transformation.