Expression, purification and characterization of non-heme iron-dependent mono-oxygenase OzmD in oxazinomycin biosynthesis.

Oxazinomycin is a C-nucleoside natural product characterized by a 1,3-oxazine ring linked to ribose via a C-C glycosidic bond. Construction of the 1,3-oxazine ring depends on the activity of OzmD, which is a mononuclear non-heme iron-dependent enzyme from a family of enzymes that contain a domain of unknown function (DUF) 4243. OzmD catalyzes an unusual oxidative ring rearrangement of a pyridine derivative that releases cyanide as a by-product in the final stage of oxazinomycin biosynthesis. The intrinsic sensitivity of the OzmD substrate to oxygen along with the oxygen dependency of catalysis presents significant challenges in conducting in vitro enzymatic assays. This chapter describes the detailed procedures that have been used to characterize OzmD, including protein preparation, activity assays, and reaction by-product identification.