Artificial metalloenzymes engineered from non-heme enzymes

众所周知，非血红素酶可以催化一系列多用途反应，产生许多复杂的天然产物。它们最常用于氧化反应，在氧化反应中经常发现含有2-己-1-羧酸三联体的活性位点。在包括卤化酶在内的其他酶中也观察到相同的基序。卤化酶如syb2、HctB和WeIO5是依赖于-酮戊二醛酶的酶，在这些酶中形成铁氧中间体，但氨基酸残基的微妙定位取代了从氧化到卤化的活性。syb2表现出混杂行为，也可以催化叠氮化和硝化，尽管产量低。该酶用于有机合成的一个限制是要求底物由ACP传递，即它只能用于功能化脂肪酸。WeIO5已被发现可以接受游离底物，从而为有机合成提供了更有前途的模板。在最近的研究中，它是WeIO5的一个变体，WeIO5*已被证明可以接受天然吲哚底物以外的底物，也可以接受NaBr和NaCl。

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.