Finally and for comparison, the inhibitory potential of the porphine
derivative meso-5,10,15,20-tetrakis-(N-methyl-4-pyridinio)porphine
(TMPyP4) (Fig. 6B, inset) was tested. This compound has so far been
known as the most powerful inhibitor of the ribozyme cleavage
reaction [32]. The kinetics of the reaction in the presence of increasing
concentrations of TMPyP4 and the determination of the IC50 are
shown in Fig. 6A and B. The results show that indeed, TMPyP4 is also a
potent inhibitor of the CChMVd-HHR self-cleavage activity with an
IC50 of 177 ± 5 nM under the conditions used in these experiments.
The kobs of the reaction decreases from 4 min − 1 in the absence of
TMPyP4 to 0 in its presence at a concentration of 3 μM.