Cytochrome (cyt) P460 is a heme-containing enzyme found in ammonia-oxidizing bacteria such as Nitrosomonas europaea that converts hydroxylamine (NH2OH) to nitrous oxide (N2O) via an {FeNO}6 intermediate. Compared to other c-type hemoproteins, this enzyme contains an additional N-C covalent attachment to the 13’ mesocarbon from a lysine residue. This crosslink has been shown to be essential for catalytic activity and confers unique spectroscopic characteristics to the protein, including a shifted Soret maximum to 460 nm in its reduced state. Biological hemes are not commonly substituted at the meso position, which makes the P460 cofactor rather unique; however, investigations into how the crosslink affects its spectroscopic properties are complicated by the protein scaffold, necessitating a small molecule to study. Mono meso-substituted cyt. P460 model complexes are being synthesized and adducts of the various nitrogen species operative in the enzyme’s catalytic cycle will be generated. These complexes will be characterized by XAS, NMR, EPR, and resonance Raman spectroscopies and compared with those of the enzyme to help us better understand how the N-C crosslink affects cyt. P460’s spectroscopic properties.

Synthesis and characterization of cytochrome P460 active site model complexes

255th National Meeting (2018)

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