The role of 2',3'-cyclic phosphodiesters in the bovine pancreatic ribonuclease A catalysed cleavage of RNA: intermediates or products?
There is a considerable degree of ambiguity in the literature regarding the role of the 2',3'-cyclic phosphodiesters formed during the reaction of RNA cleavage catalysed by ribonuclease. Usually the reaction is considered to take place in two steps: in the first step there is a transphosphorylation of the RNA 3',5'-phosphodiester bond broken yielding a 2',3'-cyclic phosphodiester which in the second step is hydrolysed to a 3'-nucleotide. Although in many occasions, either explicitly or implicitly, the reaction is treated as taking place sequentially, this is not the case as it has been shown that the 2',3'-phosphodiesters are actually released to the medium as true products of the reaction and that no hydrolysis of these cyclic compounds takes place until all the susceptible 3',5'-phosphodiester bonds have been cyclised. Comparison of the hydrolysis and alcoholysis of the 2',3'-phosphodiesters catalysed by RNase A indicates that the hydrolysis reaction has to be considered formally as a special case of the transphosphorylation back reaction in which the R group of the R-OH substrate is just H. It is thus concluded that the 2',3'-cyclic phosphodiesters formed in the ribonuclease A reaction are true products of the transphosphorylation reaction and not intermediates as usually considered.
Cuchillo
C M
CM
Departament de Bioquímica i Biologia Molecular, Facultat de Ciències, Universitat Autònoma de Barcelona, Spain.
Parés
X
X
Guasch
A
A
Barman
T
T
Travers
F
F
Nogués
M V
MV
D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D006868:Hydrolysis; D008962:Models, Theoretical; D010766:Phosphorylation; D012313:RNA / Q000378:metabolism*; D012259:Ribonuclease, Pancreatic / Q000378:metabolism*
D012313:RNA; D012259:Ribonuclease, Pancreatic; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases