Chemistry

Hothouse Catalysis

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Science  07 Jan 2011:
Vol. 331, Issue 6013, pp. 11
DOI: 10.1126/science.331.6013.11-d

Although some have said that physical organic chemistry is a field whose time has passed, it still is possible, with a bit of creativity, to extract provocative ideas from the growing compendium of chemical data collected on those most interesting of catalysts, enzymes. Stockbridge et al. begin with Arrhenius plots, which relate the logarithm of the rate constant to the reciprocal of temperature. They use these to estimate the rates of reaction of a variety of conversions, such as the hydrolysis of peptide bonds and of phosphate monoesters, and find large enhancements as the temperature increases from the common laboratory setting of 25°C to the primordial environment of 100°C, which turn out to be 3000-fold for the former and 107-fold for the latter. Why should we care? Because the rates of the slowest reactions increase the most, and thus the synthesis and transformation of small organic molecules would have flourished at 100°C. Enzymes, which make these reactions go fast enough at 25°C to sustain life today, would have been highly sought after as the ambient conditions cooled. Furthermore, lowering enthalpic barriers, as most enzymes do, is a more effective catalytic strategy than boosting entropy as temperatures drop.

Proc. Natl. Acad. Sci. U.S.A. 107, 22102 (2010).

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