Synthetic constructs functionally mimicking ribonuclease A

The mechanism of hydrolysis of RNA substrates-diribonucleoside monophosphat e CpA and decaribonucleotide UUCAUGUAAA-by chemical constructs Functionally mimicking ribonuclcase A was studied. It is shown that RNA cleavage by che mical RNases 2L2 and 2D3 proceeds similar to the RNase A-induced RNA hydrol ysis through 2',3'-cyclophosphate as an intermediate product. A comparison of hydrolyses of CpA in water and D2O revealed an isotope effect (K-H/K-D = 2.28), which implies acid-base catalysis at the limiting stage of the reac tion. Two feasible mechanisms of RNA hydrolysis by chemical RNases (linear and adjacent) are discussed.