Biosynthesis of the Central Piperidine Nitrogen Heterocycle in Series a Thiopeptides.

Summary of main observation and conclusion: Thiopeptides, arising from complex posttranslational modifications of a genetically encoded precursor peptide, are of great interest due to their structural complexity and important biological activities. All of these antibiotics share a macrocyclic peptidyl core that contains a central, six‐membered nitrogen heterocycle and are classified into five series a—e based on the oxidation state of the central nitrogenous ring. Here, we report that the biosynthesis of the central piperidine heterocycle of series a thiopeptides relies on the activity of homologues of an F420H2‐dependent reductase TppX4 by exploiting and characterizing the piperidine‐containing thiopeptin biosynthetic gene (tpp) cluster in Streptomyces tateyamensis. In vitro reconstruction of TppX4 activity demonstrated that the piperidine heterocycle of thiopeptins was transformed from a dehydropiperidine heterocycle, and TppX4 tolerated the changes in the C‐termini and macrocyclic peptidyl core of substrate and also tolerated dehyropiperidine‐containing monocyclic or bicyclic thiopeptides. The identification of TppX4 and its substrate tolerance enriches the biosynthetic toolbox for development of additional thiopeptide analogs for clinical drug screening. [ABSTRACT FROM AUTHOR]