Figure 2.

Saturation kinetics of light, ¹⁵N-labeled and heavy HIV-1 protease. Steady state kinetic rates of product formation are plotted as a function of fluorescent substrate concentration. Catalysts are 10 nM light (blue), ¹⁵N (pink), and heavy (black) HIV-1 protease. Curves were plotted as a function of initial rate (v_i) of product formation and substrate concentration and were fit to the equation v_i = k_cat[E][A]/(K_m + [A]).