An especially interesting category of genes encode for tailoring enzymes, also known as maturases. Defined as post-scaffold synthesis-acting enzymes, they act on the immature compound by installing a variety of chemical moieties, performing cyclizations or catalyzing redox reactions . These modifications often have profound impact on the biological activities of the compound. For example, in the case of microcin J25, the activity against the Gram-negative bacterial RNA-polymerase depends on the presence of the so-called lariat fold, introduced by the maturation enzymes . For the glycopeptide vancomycin, antibiotic efficacy drops by five-fold if the glycosylation introduced by the enzymes GtfD and GtfE is missing . Tailoring enzymes also show a remarkable variety in substrate specificity: while some have narrow substrate specificity (e.g., the halogenase MibH acting on NAI-107/microbisporicin A (18)), others act in a promiscuous and iterative fashion (e.g., the epimerase PoyD acting on polytheonamide A ( )). Therefore, knowledge about tailoring enzymes/maturases is not only essential in understanding the biosynthesis of a compound, but can also be leveraged for various applications: predictions of the putative products of uncharacterized BGCs, rational compound design, and biotechnological applications.