Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Nat Chem. 2013 Nov;5(11):971-7. doi: 10.1038/nchem.1777. Epub 2013 Oct 13.
Vitamins are hypothesized to be relics of an RNA world, and were probably participants in RNA-mediated primordial metabolism. If catalytic RNAs, or ribozymes, could harness vitamin cofactors to aid their function in a manner similar to protein enzymes, it would enable them to catalyse a much larger set of chemical reactions. The cofactor thiamin diphosphate, a derivative of vitamin B1 (thiamin), is used by enzymes to catalyse difficult metabolic reactions, including decarboxylation of stable α-keto acids such as pyruvate. Here, we report a ribozyme that uses free thiamin to decarboxylate a pyruvate-based suicide substrate (LnkPB). Thiamin conjugated to biotin was used to isolate catalytic individuals from a pool of random-sequence RNAs attached to LnkPB. Analysis of a stable guanosine adduct obtained via digestion of an RNA sequence (clone dc4) showed the expected decarboxylation product. The discovery of a prototypic thiamin-utilizing ribozyme has implications for the role of RNA in orchestrating early metabolic cycles.
维生素被假设为 RNA 世界的遗留物，可能是 RNA 介导的原始代谢的参与者。如果催化 RNA（核酶）能够利用维生素辅因子来帮助其发挥功能，类似于蛋白质酶，那么它们就能够催化更多种类的化学反应。辅酶硫胺素二磷酸（维生素 B1 的衍生物）被酶用于催化困难的代谢反应，包括稳定的α-酮酸（如丙酮酸）的脱羧作用。在这里，我们报告了一种核酶，它使用游离的硫胺素催化基于丙酮酸的自杀底物（LnkPB）的脱羧作用。连接生物素的硫胺素被用于从连接到 LnkPB 的随机序列 RNA 池中分离出催化个体。通过对 RNA 序列（克隆 dc4）进行消化获得的稳定鸟嘌呤加合物的分析表明，得到了预期的脱羧产物。发现了一种典型的利用硫胺素的核酶，这对 RNA 在协调早期代谢循环中的作用具有重要意义。
