New Lab-Created Enzyme May Explain Origins of Life on Earth

A certain enzyme may help explain the origins of life on Earth. Scientists have created a test tube enzyme with a unique property that may have been crucial when life was first beginning to emerge.

"When I start to tell people about this, they sometimes wonder if we're merely suggesting the possibility of such an enzyme-but no, we actually made it," said Gerald F. Joyce, senior author of the new study, in a news release.

The newly created enzyme is called a ribozyme, since it's made from ribonucleic acid (RNA). Scientists believe that DNA first evolved from simpler RNA over time and that RNA molecules with enzymatic properties were Earth's first self-replicators.

The ribozyme works by knitting together a "copy" strand of RNA, using an original RNA strand as a reference or "template." However, it doesn't make a copy of a molecule completely identical to itself. Instead, it makes a copy of a mirror image of itself. This mirror ribozyme can then help make copies of the original. Until now, no one has ever created such "cross-chiral" enzymes before.

Life on Earth evolved in such a way that each class of molecules, one chirality, or handedness, came to predominate. For example, virtually all RNA are right-handed and called D-RNA. This structural sameness makes interactions within that class more efficient. Yet it seems likely that simple RNA molecules on a primordial Earth could have consisted of mixes of both right- and left-handed forms.

In this case, the scientists decided to create a ribozyme that worked cross-chirally, on opposite-handed RNA, in order to mimic what might have been seen on primordial Earth. Using "test-tube evolution," they created a ribozyme that managed just that.

"Ultimately what one wants is to turn it loose-in the lab, of course, not in the wild-to let it start replicating and evolving and seeing what results," said Joyce.

The findings are published in the journal Nature.