The world’s first enzymes made from artificial genetic material have been created by scientists in what could be a major step towards generating synthetic life.
The enzymes, which do not occur naturally, were created using a synthetic form of DNA called XNA and were capable of triggering chemical reactions in the lab.
The findings build on previous work that showed six types of XNA molecules were capable of storing and transmitting genetic information in the same way as DNA and RNA.
It had been previously thought that DNA and RNA, which form the basis for all life on Earth, were the only way of storing genetic material.
But now the latest research by synthetic biologists in Cambridge shows that this synthetic genetic material is also capable of performing another crucial biological role - catalysing biochemical reactions that are essential for life.
Using their lab-made XNAs as building blocks, the team were able to create synthetic enzymes, which they have named ‘XNAzymes’, that could cut up and stitch together small chunks of genetic material, just like naturally occurring enzymes.
The suggests that such molecules could be used to replicate some of the earliest steps needed to produce life itself and may even provide clues about what life on other planets may be like.
It is thought that life first began with the evolution of a segment of RNA that was able to copy itself and catalyse reactions.
If XNA is also capable of this, then it could also have led to different forms of life on other planets or could be used to create new synthetic forms of life.
However, Dr Philipp Holliger, who led the research at the MRC Laboratory of Molecular Biology in Cambridge, said: ‘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.
‘Until recently, it was thought that DNA and RNA were the only molecules that could store genetic information and, together with proteins, the only biomolecules able to form enzymes.
‘Life's 'choice' of RNA and DNA may just be an accident of prehistoric chemistry.
'The creation of synthetic DNA, and now enzymes, from building blocks that don't exist in nature also raises the possibility that if there is life on other planets it may have sprung up from an entirely different set of molecules, and widens the possible number of planets that might be able to host life.’
In 2012 Dr Holliger’s group showed that there were six alternative molecules to the oligonucleotides that form RNA and DNA, which they called XNAs.
They demonstrated that these could store information and could even evolve through natural selection.
In their latest research, which is published in the journal Nature, the team created four different types of synthetic enzyme from strands of XNA.
These XNAzymes were able to perform the role of a polymerase - an enzyme that cuts and joins RNA strands together - in a test tube.
One of the XNAzymes they created was also able to join XNA strands together to form longer molecules - a key step towards creating a living system that can replicate itself.
Although it will still be some time before these can be used to create living synthetic organisms, Dr Holliger believes that XNAzymes could also be useful for developing new therapies for range of diseases including cancers and some viral infections.
Dr Holliger added: ‘Our XNAs are chemically extremely robust and, because they do not occur in nature, they are not recognised by the body's natural degrading enzymes.
‘This might make them an attractive candidate for long-lasting treatments that can disrupt disease-related RNAs.’
Professor Patrick Maxwell, chair of the MRC's Molecular and Cellular Medicine Board, said the work could kick start an entirely new branch of medicine.
He said: ‘Synthetic biology is delivering some truly amazing advances that promise to change the way we understand and treat disease.
‘This latest advance offers the tantalising prospect of using designer biological parts as a starting point for an entirely new class of therapies and diagnostic tools that are more effective and have a longer shelf-life.’
Professor Jack Szostak, a Nobel prize winner at Harvard University who studies the origins of life, added that the research raises some fundamental questions about what life on other planets may be like.
He told New Scientist: ‘The possibility that life elsewhere, on exoplanets, could have started with something other than RNA or DNA is quite interesting.
‘But the primordial biopolymer for any form of life must satisfy other constraints as well, such as being something that can be generated by prebiotic chemistry and replicated efficiently.
‘Whether XNA can satisfy these constraints, as well as providing useful functions, remains an open question.’
