Enzymes that methylate using S-adenosyl-l-methionine — nature’s methyliodide — are abundant and often promiscuous; however, a preference for alkylation over methylation has been neither observed in nature nor engineered. Now, carboxymethylation has been demonstrated using engineered methyltransferases.

中文翻译：

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挑战自然界对甲基化的偏爱。

使用S-腺苷-1-蛋氨酸（自然界的甲基碘）甲基化的酶种类丰富，并且经常是混杂的。然而，自然界中也没有观察到烷基化比甲基化的偏好。现在，已经使用工程改造的甲基转移酶证明了羧甲基化。