Ribozymes are RNA molecules that act as chemical catalysts.The hairpin ribozyme most probably uses a closely similar mechanism.The nucleolytic ribozymes comprise a class of five structurally-distinct species that bring about site-specific cleavage by nucleophilic attack of the 2?-O on the adjacent 3?-P to form a cyclic 2?,3?-phosphate.In the Varkud satellite ribozyme, we have shown that the cleavage reaction is catalysed by guanine and adenine nucleobases acting as general base and acid, respectively.