Scientists have made a breakthrough in the field of synthetic biology by creating, for the first time, enzymes from artificial genetic material that does not exist in nature. This exciting new work not only offers new insights into the origins of life on Earth, but also has implications for our search for extraterrestrial life on other planets.
The foundations for this study were laid a couple of years ago when UK scientists created synthetic versions of DNA, the molecule that carries the genetic information of all living things on Earth, and its close chemical cousin, RNA. This synthetic genetic material was created using the same building blocks that are found in DNA and RNA, but the scientists strung them together with different molecules. These resulting synthetic molecules, which were dubbed ‘XNAs,’ or xeno nucleic acid, were found to be capable of storing and passing on genetic information.
Although it was widely believed that DNA and RNA, together with proteins, were the only molecules that could form enzymes, the same researchers have now demonstrated that it is possible to create synthetic enzymes using only these XNAs. These molecules, which have been named ‘XNAzymes,’ were capable of chopping up and stitching together bits of RNA, just like natural enzymes. One of them was even capable of joining up fragments of XNA.
Enzymes, nature’s catalysts, are fundamental to life on Earth because almost all of the biochemical reactions taking place in cells are inefficient at ambient temperatures. Enzymes are therefore required to give reactions, such as synthesizing DNA or digesting food, a kick-start, allowing them to occur at rates sufficient for life to exist.
Although the majority of enzymes are proteins, some RNA molecules possess catalytic activity. It’s widely believed that the evolution of early pieces of genetic information, which may have been RNA, into self-replicating enzymes was likely a key event in the emergence of life on Earth. This work is therefore important because it recreates one of the earliest stages towards life. However, it also teases us with the possibility that life could evolve without DNA or RNA, which are widely regarded as the prerequisites for life.
“Our work suggests that, in principle, there are a number of possible alternatives to nature’s molecules that will support the catalytic processes required for life,” said lead scientist Philip Holliger. “Life’s ‘choice’ of RNA and DNA may just be an accident of prehistoric chemistry.”
Because it is possible to create genetic material and enzymes from building blocks that don’t occur naturally, this suggests that life could emerge from different molecular backbones on other planets. This could therefore “potentially widen the number of exoplanets that one could consider would be hospitable for some form of life,” according to Holliger.
This work, the researchers say, could also lead to a new wave of treatments for a variety of diseases. As explained by Dr. Holliger, it may be possible to synthesize XNAs that are capable of chopping up pieces of RNA produced from cancer genes or fragments of viral RNA. And because the XNAs don’t occur naturally, it is unlikely that they will be recognized and destroyed by other enzymes in the body.