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How do ribozymes show that some enzymes are not proteins?
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Protein
The molecular structure of a peptide (a small protein) consists of a sequence of amino acids.
Ribozymes demonstrate that not all enzymes are proteins by proving that certain nucleic acids possess catalytic activity. Historically, it was believed that all enzymes were proteins; however, the discovery of ribozymes in the 1980s refuted this axiom.12
Ribozymes are RNA molecules that function as catalysts, regulating the rate of chemical reactions without being consumed in the process. Key examples include:132
- Self-splicing introns: Thomas Cech discovered that certain RNA sequences can excise themselves from a precursor molecule and rejoin the remaining ends in an autocatalytic reaction.1
- Ribonuclease P: Sidney Altman demonstrated that the RNA component of this complex is responsible for cleaving precursor tRNA into its mature form.1
These findings indicate that catalytic functions are not exclusive to protein-based structures, supporting the hypothesis of an early "RNA world" where RNA served as both the primary catalyst and the carrier of genetic information.1