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Abstract：
A longstanding idea in evolutionary physiology is that an enzyme cannot jointly optimize performance at both high and low temperatures due to a trade-off between stability and activity. Although a stability-activity trade-off has been observed for well-characterized examples, such a trade-off is not imposed by any physical chemical constraint. To better understand the pervasiveness of this trade-off, I investigated the stability-activity relationship for comparative biochemical studies of purified orthologous enzymes identified by a literature search. The nature of this relationship varied greatly among studies. Notably, studies of enzymes with low mean synonymous nucleotide sequence divergence were less likely to exhibit the predicted negative correlation between stability and activity. Similarly, a survey of directed evolution investigations of the stability-activity relationship indicated that these traits are often uncoupled among nearly identical yet phenotypically divergent enzymes. This suggests that the presumptive trade-off often reported for investigations of enzymes with high mean sequence divergence may in some cases instead be a consequence of the degeneration over time of enzyme function in unselected environments, rather than a direct effect of thermal adaptation. The results caution against the general assertion of a stability-activity trade-off during enzyme adaptation.
摘要：
进化生理学中的一个长期想法是，由于稳定性和活性之间的权衡，酶无法在高温和低温下共同优化性能。尽管对于特征明确的例子已经观察到稳定性-活性权衡，这种权衡不受任何物理化学约束。为了更好地理解这种权衡的普遍性，我调查了通过文献检索鉴定的纯化直系同源酶的比较生化研究的稳定性-活性关系。这种关系的性质在研究中差异很大。值得注意的是,对具有低平均同义核苷酸序列差异的酶的研究不太可能表现出稳定性和活性之间的预测负相关。同样，对稳定性-活性关系的定向进化研究的调查表明，这些性状通常在几乎相同但表型不同的酶中分离。这表明，在某些情况下，经常报道的用于研究具有高平均序列差异的酶的推定权衡可能是在未选择的环境中酶功能随时间退化的结果。而不是热适应的直接影响。结果警告了在酶适应过程中稳定性-活性权衡的一般主张。
