Functional characterization of ttnI completing the tailoring steps for tautomycetin biosynthesis in Streptomyces griseochromogenes

The tautomycetin (TTN) biosynthetic gene cluster has been recently cloned and sequenced from Streptomyces griseochromogenes, unveiling four genes, ttnCDFI, as candidates to encode the tailoring steps for TTN biosynthesis. It is reported that (i) TtnC plays no essential role in TTN biosynthesis, (ii) TtnI catalyzes C-5 oxidation, and (iii) combining the previous findings with TtnFD, the tailoring steps from TTN F-1 to TTN take place in the order of TtnF-catalyzed C-1"/C-2" dehydration, TtnD-catalyzed C-3" decarboxylation, and TtnI-catalyzed C-5 oxidation.