Sengle G, Eisenführ A, Arora P S, Nowick J S, Famulok M
Kekulé-Institut für Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany.
Chem Biol. 2001 May;8(5):459-73. doi: 10.1016/s1074-5521(01)00026-6.
In vitro selected ribozymes with nucleotide synthase, peptide and carbon-carbon bond forming activity provide insight into possible scenarios on how chemical transformations may have been catalyzed before protein enzymes had evolved. Metabolic pathways based on ribozymes may have existed at an early stage of evolution.
We have isolated a novel ribozyme that mediates Michael-adduct formation at a Michael-acceptor substrate, similar to the rate-limiting step of the mechanistic sequence of thymidylate synthase. The kinetic characterization of this catalyst revealed a rate enhancement by a factor of approximately 10(5). The ribozyme shows substrate specificity and can act as an intermolecular catalyst which transfers the Michael-donor substrate onto an external 20-mer RNA oligonucleotide containing the Michael-acceptor system.
The ribozyme described here is the first example of a catalytic RNA with Michael-adduct forming activity which represents a key mechanistic step in metabolic pathways and other biochemical reactions. Therefore, previously unforeseen RNA-evolution pathways can be considered, for example the formation of dTMP from dUMP. The substrate specificity of this ribozyme may also render it useful in organic syntheses.
体外筛选出的具有核苷酸合成酶、肽和碳-碳键形成活性的核酶，有助于深入了解在蛋白质酶进化之前化学转化可能是如何被催化的。基于核酶的代谢途径可能在进化早期就已存在。
我们分离出一种新型核酶，它能在迈克尔受体底物上介导迈克尔加成物的形成，类似于胸苷酸合成酶机制序列中的限速步骤。对该催化剂的动力学表征显示其速率提高了约10⁵倍。该核酶表现出底物特异性，可作为分子间催化剂，将迈克尔供体底物转移到含有迈克尔受体系统的外部20聚体RNA寡核苷酸上。
本文所述的核酶是具有迈克尔加成物形成活性的催化RNA的首个实例，这代表了代谢途径和其他生化反应中的一个关键机制步骤。因此，可以考虑以前未预见到的RNA进化途径，例如由dUMP形成dTMP。这种核酶的底物特异性也可能使其在有机合成中有用。
