The ribosome as an entropy trap
The ribosome as an entropy trap
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DOI：
10.1073/pnas.0402488101
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发表时间：
2004-05-25
影响因子：
11.1
通讯作者：
Wolfenden, R
中科院分区：
文献类型：
--
作者：
Sievers, A;Beringer, M;Wolfenden, R
为了确定核糖体作为催化剂的有效性，我们比较了n -甲酰基甘氨酸乙二醇酯与三（羟甲基）氨基甲烷反应的非催化肽键形成速率和核糖体转移肽基的速率。根据二级速率常数对温度的依赖性，确定了两种反应的活化参数。与大多数蛋白酶相比，核糖体上的激活焓略低于溶液中。核糖体产生的2 × 10(7)倍速率增强完全是通过降低激活熵来实现的。这些结果与核糖体主要通过在活性位点定位底物和/或水排斥来提高肽键形成速率的观点一致，而不是通过传统的化学催化。
To determine the effectiveness of the ribosome as a catalyst, we compared the rate of uncatalyzed peptide bond formation, by the reaction of the ethylene glycol ester of N-formylglycine with Tris(hydroxymethyl)aminomethane, with the rate of peptidyl transfer by the ribosome. Activation parameters were also determined for both reactions, from the temperature dependence of their second-order rate constants. In contrast with most protein enzymes, the enthalpy of activation is slightly less favorable on the ribosome than in solution. The 2 x 10(7)-fold rate enhancement produced by the ribosome is achieved entirely by lowering the entropy of activation. These results are consistent with the view that the ribosome enhances the rate of peptide bond formation mainly by positioning the substrates and/or water exclusion within the active site, rather than by conventional chemical catalysis.