In 1982, Cech, along with his colleagues at the University of Colorado, discovered that certain RNA molecules could act as catalytic enzymes. This discovery challenged the long-held belief that all enzymes were proteins, and earned Cech the 1989 Nobel Prize in Chemistry.

These RNA molecules, known as ribozymes, were found to be involved in the splicing of RNA molecules in the protozoan *Tetrahymena thermophila*. This discovery opened up a new field of research in RNA biochemistry, and led to a greater understanding of the diverse roles that RNA plays in biological processes.