Triple hydroxylation of tetracenomycin A2 to tetracenomycin C involving two molecules of O-2 and one molecule of H2O

[GRAPHICS] The TcmG or ElmG oxygenase-catalyzed triple hydroxylation of tetracenomycin (Tcm) A2 to Tcm C proceeds via a novel monooxygenase-dioxygenase mechanism , deriving the 4- and 12a-OH groups of Tcm C from two molecules of O-2 and the 4a OH group of Tcm C from a molecule of H2O. These results suggest a me chanistic analogy among TcmG, ElmG, and the bacterial and fungal hydroquino ne epoxidizing dioxygenases, as well as the mammalian vitamin K-ependent ga mma-glutamyl carboxylase.