The Study Of The Functions Of Type ?Thioesterases In Streptomyces Chattanoosensis L10

Type ? thioesterases (TE?s) are acyl-acyl carrier protein (ACP) hydrolases, whose encoding genes usually locate in the polyketide synthase (PKS) and the non-ribosomal peptide synthetase (NRPS) gene clusters. In PKS/NRPS biosynthetic pathway, TE?s generally hydrolyse the aberrant extender units in the elongation steps and the unfavoured starter units in the initiation steps in order to ensure the molecular structural accuracy of final products. In some PKSs without type ? thioesterases (TE?s), TE?s can also play essential roles of TE?s, which is to release the final products from the PKSs in the termination steps.In this paper, we chose an industrial natamycin producing strain (Streptomycetes chattanoogensis L10) to study the functions of TE?s. Genome sequencing and bioinformatic analysis revealed three TE? genes:scnI in natamycin biosynthetic gene cluster, mgsB in migrastatin synthetic gene cluster, and PKSIaTE? in PKSIa synthetic gene cluster. Deletion of scnl in S. chattanoogensis significantly decreased the yield of natamycin, indicating that ScnI plays an important role in the natamycin biosynthesis. Biochemical characterization of ScnI showed that ScnI might hydrolyse the aberrant extender units in the extension steps and the unfavoured starter units in the initiation steps during the natamycin biosynthesis. Biochemical characterization of PKSIaTE? suggested that PKSIaTE? might complement the functions of ScnI. In this paper, we studied the functions of TE?s at the molecular level, revealed part of the natamycin biosynthetic pathway, and also laid a theoretical foundation for the construction of high-yielding natamycin industrial strains.