Like lifelong Floridians dropped into a Wisconsin winter, enzymes accustomed to warmth don’t always fare well in colder climes. But ancient heat-loving enzymes forced to adapt to a cooling Earth managed to swap out parts to keep chemical reactions going, scientists report online December 22 in Science,
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By reconstructing enzymes as they might have looked billions of years ago, the research “helps to explain the natural evolutionary history of life on this planet,
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,” says Yousif Shamoo, a biochemist at Rice University in Houston who wasn’t part of the study. And the findings question the idea that enzymes must sacrifice their stability to become more active.
Enzymes are natural catalysts that jump-start essential chemical reactions inside living things. Most work only within a specific temperature range. Too cold,
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, and they can’t get going. Too hot, and they lose their shape — and by extension, their function.
Life on Earth is believed to have started out in warm environments like hot springs or hydrothermal vents,
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, so the first enzymes probably worked best in those toasty temperatures, says study coauthor Dorothee Kern,
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, a biochemist at Brandeis University in Waltham,
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, Mass. But gradually, Earth cooled. For life to continue,
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, early enzymes had to shift their optimal temperature range.
Kern and her colleagues looked at the evolutionary history of an enzyme called adenylate kinase. Some version of this protein is found in every cell,
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,

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