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Evolutionary trade-offs in natural versus engineered enzymes

PI(s): Scott Miller (University of Montana-Missoula (Missoula,MT))
Start Date: 10-Mar-2012
End Date: 15-May-2012
Keywords: adaptation, thermal biology, natural selection, molecular biology

A longstanding idea in evolutionary physiology is that an enzyme can’t be good at its job at both high and low temperatures. The idea is based on our intuition that the changes in a protein which make it more stable at high temperature invariably slow its activity at lower temperatures. That is, a rigid protein may better resist unfolding but is also less flexible to perform the movements required for its function. This results in a trade-off in performance at physiological extremes. We know of many examples of this trade-off from comparisons among related enzymes of organisms adapted to different temperatures. No law of physical chemistry imposes this trade-off, however, and recent work on enzymes engineered in the absence of organisms has revealed a growing number of exceptions to this idea. Nonetheless, for both natural and engineered enzymes, we still lack a comprehensive synthesis of available data required to address the relative strength of support for a trade-off between thermostability and catalytic activity. Here, I appraise the merits of the trade-off hypothesis for both natural and engineered enzymes. I also seek to provide a possible explanation for any observed difference between these enzyme categories. The project promises novel insights into the nature of the biological constraints on enzyme adaptation.