Evolution on the Molecular Level: From Bacteria to Humans

Evolution helped shape our world the way it appears today. This evolution, though, also occurred at the molecular level; it reshaped some of the enzymes that help complete crucial chemical processes. Now, scientists have described the evolution of the various forms of the enzyme "dihydrofolate reductase" as it occurred from bacteria to humans, revealing a bit more about how life functions today.

In order to learn a bit more about evolution in this particular enzyme, the researchers used bioinformatics, computer-based calculations, artificial mutagenesis and kinetic measurements. They studied "humanized" forms of an enzyme that originated with the common bacterium E. coli in order to relate the action of protein dynamics and catalysis to the process of enzyme evolution.

"Enzymes are critical components of every living cell, and they catalyze almost all chemical reaction in life," said Amnon Kohen, one of the researchers, in a news release. "This study is an attempt to understand how evolution of the whole organism (for example from bacteria like E. coli to humans) is expressed on the molecular level. We chose a 'housekeeping' enzyme, which is present in almost all organisms and is critical to life."

The researchers produced "humanized" bacterial enzyme by modifying parts of the enzyme to have the amino-acids sequences of the human enzyme. This "bridged" between the bacterial and human enzymes. This was done based on a comparison of enzyme sequences of many organisms ranging from bacteria to human.

So what did they find? It turns out that while many steps of the catalytic cascade of these enzymes are evolving, the actual chemical conversion catalyzed by the enzymes is conserved along evolution. This means that even in the bacteria, the enzyme already has perfectly oriented the reactants on its active site.

"The findings significantly affects how the scientific community understands what was important for evolutionary pressure to preserve and what is unimportant," said Kohen in a news release. "For example, the preservation of enzyme dynamics that are involved in catalyzing the chemical conversion are very fast and were not expected to play a role in evolution, thus our findings will bring researchers to consider such fast dynamics not only in evolution, but also in the design of drugs used against this enzyme (and maybe enzymes in general) or the design of bio-mimetic catalysts."

The findings are published in the Journal of Biological Chemistry.