A new post-PKS modification process in the carbamoyltransferase gene inactivation strain of Streptomyces hygroscopicus 17997.

Genetic manipulation of geldanamycin (GDM) producer Streptomyces species is a rational approach to understand biosynthesis processes and create new analogues. In this study, the carbamoyltransferase gene gdmN was inactivated by insertion of an apramycin-resistance gene aac3 (IV) into the genome of the geldanamycin-producing strain Streptomyces hygroscopicus 17997. GDM analogues produced by this mutant strain were isolated and characterized, such as new compound 4,5-dihydro-7-O-descarbamoyl-7-hydroxy-19-O-glycylgeldanamycin. This compound could be converted to compound 4,5-dihydro-19-O-glycylgeldanamycin, another new GDM analogue, by a strain of Streptomyces hygroscopicus 17997 in which the GDM-pks was inactivated. These new compounds exhibited reductions of cytotoxicity against HepG2 cancer cells, but increases of aqueous solubility. These results suggest that a new post-polyketide synthase modification was involved in this process to produce new GDM analogues.