AbstractMethylation reactions are of significant interest when generating pharmaceutically active molecules and building blocks for other applications. Synthetic methylating reagents are often toxic and unselective due to their high reactivity. S‐Adenosyl‐l‐methionine (SAM)‐dependent methyltransferases (MTs) present a chemoselective and environmentally friendly alternative. The anthranilate N‐MT from Ruta graveolens (RgANMT) is involved in acridone alkaloid biosynthesis, methylating anthranilate. Although it is known to methylate substrates only at the N‐position, the closest relatives with respect to amino acid sequence similarities of over 60 % are O‐MTs catalysing the methylation reaction of caffeate and derivatives containing only hydroxyl groups (CaOMTs). In this study, we investigated the substrate range of RgANMT and a CaOMT from Prunus persica (PpCaOMT) using compounds with both, an amino‐ and hydroxyl group (aminophenols) as possible methyl group acceptors. For both enzymes, the reaction was highly chemoselective. Furthermore, generating cofactor derivatives in situ enabled the transfer of other alkyl chains onto the aminophenols, leading to an enlarged pool of products. Selected MT reactions were performed at a preparative biocatalytic scale in in vitro and in vivo experiments resulting in yields of up to 62 %.
摘要 甲基化反应在生成具有医药活性的分子和用于其他应用的构件时具有重要意义。合成甲基化试剂由于反应活性高,通常具有毒性和非选择性。依赖 S-腺苷-l-蛋氨酸(SAM)的甲基转移酶(MTs)提供了一种化学选择性和环境友好型的替代方法。Ruta graveolens 中的蚁酸 N-MT(RgANMT)参与吖啶酮生物碱的生物合成,将蚁酸甲基化。虽然已知它只能在 N 位甲基化底物,但氨基酸序列相似度超过 60% 的近亲是催化咖啡酸酯和仅含羟基的衍生物(CaOMTs)甲基化反应的 O-MTs 。在这项研究中,我们使用同时含有氨基和羟基(氨基苯酚)的化合物作为可能的甲基受体,研究了 RgANMT 和一种来自柿树的 CaOMT(PpCaOMT)的底物范围。这两种酶的反应都具有高度化学选择性。此外,原位生成辅助因子衍生物可以将其他烷基链转移到氨基苯酚上,从而扩大产物库。在体外和体内实验中,以制备生物催化的规模进行了选定的 MT 反应,结果产率高达 62%。