The research group of Tang utilitarian, Shanghai Institute of organic science, Chinese Academy of Sciences has made important progress in the study of self resistance mechanism of naridimycin biosynthesis pathway

Bacteria produce antibiotics with biological activity through secondary metabolism so as to eliminate dissidents and compete for resources in the environment How can antibiotic producing bacteria avoid the harm of antibiotics to themselves? Recently, Tang utilitarian, a research group of State Key Laboratory of life organic chemistry, Shanghai Institute of organic chemistry, Chinese Academy of Sciences, discovered a secreted fad dependent oxidoreductase Napu in the process of biosynthesis research of high activity natural product nardinomycin (NDM), which can oxidize inactive precursors and generate nardinomycin with biological activity Later, naridinomycin can be further oxidized to inactivate it The results were recently published in the proceedings of the American Academy of Sciences (PNAs, DOI: 10.1073 / PNAS 1800502115) Naridinomycin is a natural product of tetrahydroisoquinoline family, which has attracted much attention due to its good antitumor and antibacterial activities All of them have functional semiacetaldehyde amines, in which the hydroxyl group is dehydrated by protonation, and an electrophilic imine species is formed along with the N atom The carbon atom of the imine is easily attacked by the 2-N atom in guanine to alkylate DNA effectively Gene knockout studies showed that the mutant with inactivated gene Napu produced the intermediate 5 without hemiacetal amine hydroxyl by fermentation In vitro enzyme activity test showed that Napu could oxidize compound 5 rapidly to produce NDM, while with the extension of reaction time, NDM was slowly transformed into compound 7 with amide structure Through the time gradient monitoring of the fermentation products of the wild-type naridinomycin producing strain, the author found that the production changes of NDM and compound 7 were consistent with the results of in vitro enzyme activity test The activity of compounds 5 and 7 was much lower than that of NDM Based on these experimental results, the team proposed that this extracellular oxidative activation to produce antibiotics and further oxidative inactivation process may be a self resistance mechanism of the bacteria; then combined with mutation and labeling experiments, the team proposed a possible reaction mechanism; through Western blot and protein mass spectrometry, the secretory protein Napu expressed by wild-type strains was identified Mass spectrometry imaging showed that there was a significant spatiotemporal correlation with intermediates and products, while E.coli Expressing Napu showed significant resistance to NDM This study revealed a complex and delicate mechanism of time-space isolation self resistance, which is rare in prokaryotes, including "inactivation of intracellular pharmacophore, prodrug secretion and maturation, regeneration of extracellular pharmacophore, and regulation of concentration of active antibiotics around the host", further suggesting that streptomyces is rich in complex and diverse extracellular physiological and biochemical characteristics The above achievements were mainly completed by Dr Zhang Yue, a research group of Tang utilitarian, and Dr Wen Wanhong, a doctoral student This work has been greatly supported by NSFC, Shanghai Municipal Science and Technology Commission and special program for strategic leading science and Technology (category B) of Chinese Academy of Sciences.