The responses of enzyme ( E ) and mRNA concentrations with different k
values. First the reference signal r was set to 0.5. By adjusting the protein synthesis rate (ktrnl), the same steady state values of mRNA (i.e. mRNAss = (kED · Ess + r)/ktrnl = 0.5) and enzyme concentrations were produced. At t = 50 seconds, the reference signal r was changed from 0.5 to 0.4.