Metabolic engineering of a methyltransferase for production of drug precursors demecycline and demeclocycline in .

Demecycline (DMTC) and demeclocycline (DMCTC) are C6-demethylated derivatives of tetracycline (TC) and chlortetracycline (CTC), respectively. They are precursors of minocycline and tigecycline, which showed remarkable bioactivity against TC-resistant bacteria and have been used clinically for decades. In order to biosynthesize drug precursors DMTC and DMCTC, the function of a possible C-methyltransferase encoding gene was studied systematically in the CTC high-yielding industrial strain F3. The mutant accumulated two new products, which were turned out to be DMTC and DMCTC. Meanwhile, time-course analysis of the fermentation products detected the epimers of DMTC and DMCTC transformed spontaneously. Finally, an engineering strain with higher productivity of DMCTC was constructed by deleting and overexpressing of three extra copies simultaneously. Construction of these two engineering strains not only served as a successful example of synthesizing required products through metabolic engineering, but also provided original strains for following elaborate engineering to synthesize more effective tetracycline derivatives.