Breaker Ronald R, Emilsson Gail Mitchell, Lazarev Denis, Nakamura Shingo, Puskarz Izabela J, Roth Adam, Sudarsan Narasimhan
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA.
RNA. 2003 Aug;9(8):949-57. doi: 10.1261/rna.5670703.
It is widely believed that the reason proteins dominate biological catalysis is because polypeptides have greater chemical complexity compared with nucleic acids, and thus should have greater enzymatic power. Consistent with this hypothesis is the fact that protein enzymes typically exhibit chemical rate enhancements that are far more substantial than those achieved by natural and engineered ribozymes. To investigate the true catalytic power of nucleic acids, we determined the kinetic characteristics of 14 classes of engineered ribozymes and deoxyribozymes that accelerate RNA cleavage by internal phosphoester transfer. Half approach a maximum rate constant of approximately 1 min(-1), whereas ribonuclease A catalyzes the same reaction approximately 80,000-fold faster. Additional biochemical analyses indicate that this commonly encountered ribozyme "speed limit" coincides with the theoretical maximum rate enhancement for an enzyme that uses only two specific catalytic strategies. These results indicate that ribozymes using additional catalytic strategies could be made that promote RNA cleavage with rate enhancements that equal those of proteins.
人们普遍认为，蛋白质主导生物催化的原因在于，与核酸相比，多肽具有更高的化学复杂性，因此应该具有更强的酶活性。与这一假设相符的是，蛋白质酶通常表现出比天然和工程化核酶所实现的化学速率增强更为显著的情况。为了研究核酸的真正催化能力，我们测定了14类通过内部磷酸酯转移加速RNA切割的工程化核酶和脱氧核酶的动力学特征。其中一半接近最大速率常数约为1分钟⁻¹，而核糖核酸酶A催化相同反应的速度快约80000倍。进一步的生化分析表明，这种常见的核酶“速度限制”与仅使用两种特定催化策略的酶的理论最大速率增强相吻合。这些结果表明，可以制造出使用额外催化策略的核酶，以促进RNA切割，其速率增强与蛋白质相当。
