Cytochrome P460 Cofactor Maturation Involves a Peroxide- Dependent Post-Translational Modification

Cytochrome P460s are heme enzymes that oxidize hydroxylamine to nitrous oxide as part of the biogeochemical nitrogen cycle. They bear unique “heme P460” cofactors that are cross-linked to their host polypeptides by a post-translationally modified lysine residue. Wild-type N. europaea cytochrome P460 may be isolated as a cross-link deficient proenzyme following anaerobic overexpression in E. coli. When treated with peroxide, This proenzyme undergoes complete maturation to active enzyme with spectroscopic properties that match wild-type cyt P460. Together, these data indicate that the cofactor is primed to undergo this covalent modification by virtue of the protein fold. A putative mechanism analogous to that used by heme oxygenases to degrade hemes is proposed.