History and Background
In 1967, Carl Woese, Francis Crick and Leslie Orgel hypothesized that RNA molecules could be used as catalysts based on their complex secondary structures. It was not until 1982 when Thomas R. Cech first showed that RNA molecules could be used as catalysts of chemical reactions, for which he won the Nobel prize along with Sidney Altman in 1989. However, the term "ribozyme" was coined by Kelly Kruger et al in a paper published in Cell in 1982. Since then, ribozymes have proven to be an important area of research in gene technology (Wikipedia).
Function in Natural Systems
The existence of ribozymes in natural systems is fairly rare, which is not to say that they are not important. In essense, the active part of the ribosome that translates RNA can be considered a ribozyme. Some examples of known ribozymes are listed below (such as the hammerhead ribozyme, which is of particular interest for its property of self-cleaving catalytic activity) (Wikipedia).
Types of Natural Ribozymes
- Peptidy transferase 23S rRNA
- RNase P
- Group I and Group II introns
- Hairpin ribozyme
- Hammerhead ribozyme
- Hepatitis delta virus (HDV) ribozyme
- Mammalian CPEB3
- Varkud satellite (VS) ribozyme
- Glucosamine-6-phosphate activated ribozyme glmS ribozyme
- Beta-globin co-transcriptional cleavage ribozyme CoTC ribozyme
Structure of a hammerhead ribozyme
RNA world hypothesis
Walter Gilbert proposed in 1986 that in the cell's ancient past, RNA was used both for carrying genetic material and for catalyzing chemical reactions, unlike the classical division between DNA and proteins. This theory is known as the "RNA world hypothesis" and became a popular view for the origin of cellular function. According to this theory, RNA preceded DNA as the method for transmition of cellular information by acting as both an enzyme and a nucleic acid (Wikipedia).