A Novel Cyclopentane Pyridine Compound Identified from Saccharothrix syringae NRRL B-16468 by PPTase-Based Activation

Phosphopantetheinyl transferases (PPTases) catalyze the phosphopantetheinylation of carrier proteins involved in primary and secondary metabolism. The overexpression of PPTase has been demonstrated to be an effective strategy for activating cryptic biosynthetic pathways related to secondary metabolites. Over 30 biosynthetic gene clusters encoding polyketide or nor-ribosomal peptide compounds have been identified in Saccharothrix syringae NRRL B-16468. However, with the exception of nocamycin, all other metabolites encoded by these clusters remain unidentified. In this study, we first identified the PPTase genes present in the genome of S. syringae NRRL B-16468. The subsequent overexpression of the Sfp-type PPTase gene QFZ22139 led to the generation of a novel compound saccharoridine. Saccharoridine was isolated and characterized as a cyclopentane[c]pyridine based on high-resolution mass spectrometry and comprehensive nuclear magnetic resonance spectroscopic analysis. Additionally, saccharoridine exhibited no antibacterial or antitumor activity. This study presents the first cyclopentane[c]pyridine compound isolated from a bacterial source.