Mimicking natural evolution in a test tube, scientists at The Scripps Research Institute have devised an enzyme with a unique property that might have been crucial to the origin of life. Aside from illuminating one possible path for life’s beginnings, the achievement is likely to yield a powerful tool for evolving new and useful molecules.
"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, professor in TSRI’s Departments of Chemistry and Cell and Molecular Biology and director of the Genomics Institute of the Novartis Research Foundation.
The new enzyme is called a ribozyme because it is made from ribonucleic acid (RNA). Modern DNA-based life forms appear to have evolved from a simpler "RNA world," and many scientists suspect that RNA molecules with enzymatic properties were Earth’s first self-replicators.
The new ribozyme works essentially in that way. It helps knit 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, like the left hand to its right, and, in turn, that "left-hand" ribozyme can help make copies of the original.
No one has ever made such "cross-chiral" enzymes before. The emergence of such enzymes in a primordial RNA world, which the new study shows was plausible could have overcome a key obstacle to the origin of life.