Characterization of the terminal activation step catalyzed by oxygenase CmmOIV of the chromomycin biosynthetic pathway from streptomyces griseus

Inactivation and initial interrogation of key oxygenase CmmOIV of the biosynthetic pathway of chromomycin A₃ in Streptomyces griseus ssp. griseus revealed that a completely methylated and acetylated prechromomycin is the preferred substrate of this enzyme. This suggests that the three sugar decoration reactions, two O-acetylations and an O-methylation, which were previously believed to occur as the final steps of chromomycin A₃ biosynthesis, indeed take place prior to the CmmOIV reaction. Upon inactivation of CmmOIV, four new compounds accumulated; the fully decorated prechromomycin and its incompletely acetylated precursor along with a diketoprechromomycin-type compound were fully characterized and assayed with CmmOIV.