Spermine could have also altered the kinetics of the cleavage
through increasing the rate of the ligation reaction. This is very unlikely
since that would have shifted the value of the reaction equilibrium, an
effect which is not observed. In addition, it was shown previously that
the 65% maximal cleavage at the end of the reaction did not change
upon addition of an excess of the large product of cleavage to the
incubation mixture, indicating that the plateau does not correspond to
an equilibrium but to the presence of an inactive conformation of the
ribozyme. It might be that this inactive conformation is stabilized by
the polyamine.