Table 1.

Natural ribozymes and what they do

Ribozyme	Number identified	Biological source	Reaction catalysed (product)
Group I introns	>1000	Eukaryotes (nucleus and mitochondria), prokaryotes, bacteriophages	Self-splicing transesterification (3’-OH)
Group II introns	>700	Eukaryotes (organelles), prokaryotes	Self-splicing transesterification (3’-OH)
Group-I intron like	6	Didymium, Naeglaria	Hydrolysis (3’-OH)
RNase P RNA	>300	Eukaryotes (nucleus and organelles), prokaryotes	Hydrolysis (3’-OH)
Hammerhead ribozyme	11	Plant viroids and satellite RNAs, newt	Self-cleaving transesterification (2’,3’-cyclic phosphate)
Hairpin ribozyme	4	Plant viroids and satellite RNAs	Self-cleaving transesterification (2’,3’-cyclic phosphate)
Hepatitis delta virus ribozyme	2	Human hepatitis delta virus	Self-cleaving transesterification (2’,3’-cyclic phosphate)
VS ribozyme	1	Neurspora mitochondria	Self-cleaving transesterification (2’,3’-cyclic phosphate)
Ribosomal RNAs	>5000	Eukaryotes, prokaryotes	Peptidyl transfer (peptide bond)
Spliceosomal RNAs	>100	Eukaryotes	Trans-splicing transesterification (3’-OH)