FIGURE 3. Saturation plot for the bimolecular reaction involving the final selected ribozyme and an RNA substrate, both of which contained only D and U residues.

Initial rates were determined for the ligation reaction involving 0.25–25 nM ribozyme and a trace amount of [5'-³²P]-labelled substrate. The reaction mixture contained 100 mM MgCl₂, 0.01% SDS and 30 mM CHES (pH 9.0), which was incubated at 23 °C. Each value for k_obs represents the average of three independent experiments, with the error bars corresponding to one standard deviation. The data were fit to a Michaelis–Menten saturation plot to obtain a k_cat of 0.0041 0.0006 h^-1 and K_m of 1.6 0.9 nM. The k_cat was adjusted to account for a 6% maximum extent of reaction, giving a value of 0.068 0.010 h^-1.