FIGURE 3.

A, catalytic activity rescue of mixed R51A and R239A mutants. Decay of the substrate, ACMS, in the first minute was monitored by UV-visible spectroscopy at 360 nm. Autodecay of substrate (black trace), in the presence of R51A (red trace), and in the presence of R239A (blue trace) are three overlapping lines. R51A and R239A were premixed on ice for 1 h (green trace), 7 h (pink trace), and 24 h (tan trace), respectively. B, the rescued activity increased as a function of incubation time of the two mutants. The data were fit to Equation 10. The incubation and kinetic reaction are done at room temperature. C, Michaelis-Menten kinetics of the 1:1 mixed R51A and R239A after 48 h of equilibration.