Ribozymes and the mechanisms that underlie RNA catalysis

Ribozymes are widespread, and catalyze some extremely important reactions in the cell. Mechanistically most fall into one of two classes, using either metal ions or general acid-base catalysis. The nucleolytic ribozymes fall into the latter class, mostly using nucleobases. A sub-set of these use a combination of guanine base plus adenine acid to catalyze the cleavage reaction. New ribozymes are still being discovered at regular intervals and we can speculate on the potential existence of ribozymes that catalyze chemistry beyond phosphoryl transfer reactions, perhaps using small-molecule coenzymes. [Figure not available: see fulltext.]