( Re-think ( ( on ribozymes ) ( ( ( ( ( ( Until ( the ( late 1980s ) ) ) ( , ( ( protein enzymes ) ( were ( thought ( to ( be ( the ( only ( biological catalysts ) ) ) ) ) ) ) ) ) ) , ) then ) ( ( ( catalytic ( RNA molecules ) ) ( -LRB- ( ribozymes -RRB- ) ) ) ( were discovered ) ) ) . ) ) )
(ROOT (S (ADVP (RB Re-think)) (PP (IN on) (NP (NNS ribozymes))) (S (PP (IN Until) (NP (DT the) (JJ late) (NNS 1980s))) (, ,) (NP (NN protein) (NNS enzymes)) (VP (VBD were) (VP (VBN thought) (S (VP (TO to) (VP (VB be) (NP (DT the) (JJ only) (JJ biological) (NNS catalysts)))))))) (, ,) (RB then) (S (NP (NP (JJ catalytic) (NNP RNA) (NNS molecules)) (PRN (-LRB- -LRB-) (NP (NNS ribozymes)) (-RRB- -RRB-))) (VP (VBD were) (VP (VBN discovered)))) (. .)))
Re-think on ribozymes Until the late 1980s, protein enzymes were thought to be the only biological catalysts, then catalytic RNA molecules (ribozymes) were discovered.
(ROOT (S (NP (NP (DT The) (NN discovery)) (PP (IN of) (NP (NNS ribozymes)))) (VP (VBD nullified) (NP (DT the) (NN idea)) (SBAR (IN that) (S (NP (DT all) (JJ biological) (NNS catalysts)) (VP (VBP are) (NP (NNS proteins)))))) (. .)))