Another reaction database is BRENDA, which organizes enzyme information based on the International Union of Biochemistry and Molecular Biology Enzyme Commission (EC) number nomenclature . For each EC number, BRENDA aggregates information on function, genetic context and occurrence, structure and specificity, reaction schemes, and other enzyme metadata. However, the reliance on EC numbers as base for entries lacks the flexibility required for describing the intricacies of NP biosynthetic reactions. While some NP-acting tailoring enzymes are covered by BRENDA (e.g. the erythromycin 12-hydroxylase with EC 1.14.13.154), the reconstruction of reactions from scaffold to mature product would be challenging in the majority of cases (e.g., for erythromycin, only two of five post-scaffold synthesis tailoring steps currently have EC numbers). Furthermore, the exact reaction mechanism and substrates of many NP acting enzymes are still unknown, hampering classification using EC numbers.