Literature model average. A) Model averages of Table 2 were equally weighted to form the literature average in Eq. (9) (thick line). B) The literature average was extrapolated to [ET] in the range of [ST]. Although solutions to Eqs. (2-4) match their rational polynomial approximation in Eq. (7) at [ET] = 0.0001 μM (o), this approximation fails at [ET] = 0.1 μM (Δ) and fails drastically at [ET] = 0.6 μM (+). All six of the 3-parameter mass action models (dashed lines) fit the literature average at [ET] = 0.0001 μM (o) but diverge in their extrapolated predictions at [ET] = 0.1 μM and [ET] = 0.6 μM.