Ribozymes are RNA molecules with catalytic activity. These generally involve transesterification reactions, and most are concerned with RNA metabolism (splicing and endoribonuclease). Impoant: Recently, a rRNA component has been implicated in hydrolyzing an aminoacyl ester and thus to play a central role in peptide bond function - peptidyl transferases. These observations, made using RNA molecules derived from the organelles from plants, yeast, viruses, and higher eukaryotic cells, show that RNA can act as an enzyme, and have revolutionized thinking about enzyme action and the origin of life itself. Evidence that rRNA is a Peptidyltransferase Ribosomes can make peptide bonds even when proteins are removed or inactivated Ceain pas of the rRNA sequence are highly conserved in all species These conserved regions are on the surface of the RNA molecule. RNA can be catalytic Mutations that result in antibiotic resistance at the level of protein synthesis are more often found in rRNA than in the protein components of the ribosome X-ray crystal structure of large subunit bound to tRNAs suggest detailed mechanism Ref: Weil P. (2011). Chapter 37. Protein Synthesis & the Genetic Code. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e