Artificial metalloenzymes engineered from non-heme enzymes

Non-heme enzymes are known to catalyse a whole range of versatile reactions given rise to numerous complex natural products. They are most commonly known for oxidative reactions, in which active sites containing 2-his-1-carboxylate triad are often found. This same motif is also observed in other classes of enzymes including the halogenases. Halogenases such as SyrB2, HctB and WeIO5 are -ketoglutarase dependent enzymes, in which an iron-oxo intermediate is formed but subtle positioning of the amino acid residues displace the activity from oxidation to halogenation. SyrB2 shows promiscuous behaviour and can also catalyse azidation and nitration, albeit with low yields. One limitation of this enzyme for use in organic synthesis is the requirement for the substrate to be delivered by a ACP i.e. it can only be used to functionalise fatty acids. WeIO5 has been found to accept free substrates and thus provides a more promising template for organic synthesis. In recent work it has been a variant of WeIO5, WeIO5* has been shown to accept substrates beyond its natural indole substrates and to also accept NaBr alongside NaCl.