ribozyme

Ribozyme Enzymology: "Ribozymes are antisense RNA molecules that have catalytic activity. They function by binding to the target RNA moiety through Watson-Crick base pairing and inactivate it by cleaving the phosphodiester backbone at a specific cutting site.

Five classes of ribozymes have been described based on their unique characters in the sequences as well as three-dimensional structures (Bunnell,1997). They are denoted as (1) the Tetrahymena group I intron, (2) RNase P, (3) the hammerhead ribozyme, (4) the hairpin ribozyme, and (5) the hepatitis delta virus ribozyme. They may catalyze self-cleavage (intramolecular or 'in-cis' catalysis) as well as the cleavage of external substrates (intermolecular or 'in-trans' catalysis) (Ohkawa, 1995). "

Ribosomes are large intracellular aggregates attached to the endoplasmic reticulum. They comprise several RNAs and scores of proteins, and function as ribozymes.