Ruminations on How Enzymes Evolved

By Kaiser, Jocelyn | Science News, March 4, 1995 | Go to article overview

Ruminations on How Enzymes Evolved


Kaiser, Jocelyn, Science News


It's not quite Jurassic Park, but researchers are getting closer to recreating extinct life -- or at least extinct molecules. Working backwards from the molecular structures of digestive enzymes in cattle and their modern relatives, a Swiss research team claims to have synthesized ancestral forms of these enzymes from millions of years ago.

In the process, they have found biochemical clues to the evolution of the molecules.

The team, led by Steven A. Benner of the Swiss Federal Institute of Technology (ETH) in Zurich, is among the first to recreate possibly ancient molecules in the laboratory and to compare the results with fossil evidence.

"It's kind of like using a DNA synthesizer [a machine that can assemble genes] as a time machine," says Clyde A. Hutchison III of the University of North Carolina at Chapel Hill. "It's just one molecule, but this is really exciting."

Benner and his colleagues studied a protein, a form of the enzyme ribonuclease, that breaks down bacterial RNA in the digestive systems of cows, sheep, deer, giraffes, and other ruminants.

The fossil record shows that these creatures' common ancestor, a small, deerlike animal, branched off from nonruminants 40 million years ago by developing the rumen, a stomach chamber that holds cellulose-chomping bacteria. With these bacteria, and with enzymes such as ribonuclease to digest the bacteria, ruminants can thrive on fibrous plants such as grass.

The 124 amino acids that make up this ribonuclease vary slightly among modern ruminants. …

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