Ribozyme

A ribozyme (from ribonucleic acid enzyme, also called RNA enzyme) is an RNA molecule, that catalyzes a chemical reaction. Many natural ribozymes catalyze either their own cleavage or the cleavage of other RNAs, but they have also been found to catalyze the aminotransferase activity of the ribosome. Investigators studying the origin of life have produced ribozymes in the laboratory that are capable of catalyzing their own synthesis under very specific conditions.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Before the discovery of ribozymes, proteins were the only known biological catalysts. In 1967, Carl Woese, Francis Crick, and Leslie Orgel were the first to suggest that RNA could act as a catalyst based upon findings that it can form complex secondary structures. The first ribozyme was discovered in the 1980s by Thomas R. Cech, who was studying RNA splicing in the ciliated protozoan Tetrahymena thermophila. This ribozyme was found in the intron of an RNA transcript and removed itself from the transcript. Ribozymes often have divalent metal ions such as Mg2+ as cofactors. In 1989, Thomas R. Cech and Sydney Altman won the nobel prize in chemistry for their "discovery of catalytic properties of RNA." Nobel prize announcement

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Although ribozymes are quite rare in the cell, their roles are sometimes essential to life. For example, the functional part of the ribosome, the molecular machine that translates RNA into proteins, is fundamentally a ribozyme.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

RNA can also act as a hereditary molecule, which encouraged Walter Gilbert to propose that in the past, the cell used RNA as both the genetic material and the structural and catalytic molecule, rather than dividing these functions between DNA and protein as they are today. This hypothesis became known as the "RNA world hypothesis" of the origin of life.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

If ribozymes were the first molecular machines used by early life, then today's remaining ribozymes -- such as the ribosome machinery -- could be considered living fossils of a life based primarily on nucleic acids.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A recent test-tube study of prion folding suggests that an RNA may catalyze the pathological protein conformation in the manner of a chaperone enzyme.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Some known ribozymes include RNase P, Group I and Group II introns, leadzyme, hairpin ribozyme, hammerhead ribozyme, hepatitis delta virus ribozyme, and tetrahymena ribozyme.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

RNA: Ribonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. It is biochemically distinguished from DNA by the presence of an additional hydroxyl group, attached to each pentose ring. While RNA usually contains uracil instead of thymine, this is not always true, f...

Enzyme: An enzyme (from Greek ?nsimo (??????), formed by ?n = at or in and simo = leaven or yeast) is a protein that catalyzes, or speeds up, a chemical reaction....

Molecule: A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. The science of molecules is called molecular chemistry or molecular physics, depending on the particular aspect of focus. Molecular chemistry is concerned with the laws gover...