Wednesday, February 6, 2013

Creating enzymes with artificial evolution

It is impossible to create a functional multicellular organism from ordinary 'dead' matter without having the right set of molecules that allow for chemical reactions in the body, which is called metabolism. In order to be able to convert one product into the other, for example turning food into energy, bodies need enzymes. Because the required chemistry in the body is unlikely to happen by chance alone, enzymes are there to speed up the process, by favouring the conditions for a chemical reaction between specific compounds. Enzymes are therefore important and were created very early in evolution, as without them, it is very hard to produce something that is alive. Scientists have great interest in the artificial production of enzymes, something that would allow us to produce things of our own choice. A group of researchers has found a way to let evolution run its course in the artificial production of enzymes.

According to the University of Minnesota, it is possible to create our own enzymes by something called directed evolution. Specifically, they produced a large set of enzymes that all had different functions, which were subsequently selected for the desired capabilities. During the selection process, only the 'fittest' enzymes were able to survive, which is pretty much the same as natural selection. Eventually, only the enzyme with the required properties remained.
Many labs are currently trying to create artificial enzymes, being proteins with chemical properties that we do not find in nature. Design is mostly based on computerized models, and if the scientists from Minnesota are right, they are now the first ones to adopt a strategy that is based on natural selection. Using directed evolution has a large advantage over computer design when exact information about how the to-be-produced enzyme should look like is lacking. Obviously, when you do not know how a desired chemical property can be captured in structure, it is of no use to build a computer model.

The enzyme they created has a relatively simple function: it connects RNA molecules to each other. RNA is a derivative of DNA, and is produced when our genetic code is 'read', and a transcript is made. From the RNA information, specific cellular structures create amino acid chains, which later on are turned into proteins. Our cells contain many ligases, including those ligases that bind RNA. However, the one produced from the University of Minnesota is quite different than what a normal ligase looks like. And so far, it remains unclear to what extent the artificial enzyme is useful. Nevertheless, this is an interesting proof of concept, and a good use of evolution.

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