Kinetic analysis of a general model of activation of aspartic proteinase zymogens involving a reversible inhibitor. II. Contribution of the uni- and bimolecular activation routes

Figures & data

Scheme 1 Model of autocatalytic activation of aspartic proteinase zymogens in the presence of a reversible inhibitor of the proteinase.

Figure 1 Time course of [E]_u, [E]_b and [E]_a according to Equations (3), (4) and I-(19) and from the numerical integration of the set of differential Equations 4-8 and (13). The set of values used for the equilibrium constants, rate constants and initial concentrations were the same as in Figure I-1, i.e.: K₁ = 100, K₄ = 0.005 M, k₂ = 0.005 s^-1, k₃ = 600 M^-1 s^-1, [E]₀ = 10 nM, [Z]₀ = 1 μ M and [I]₀ = 0.1 mM. In each case the progress curves from the equation and from the simulation overlap in the scale used.

Scheme 2 A simpler model for activation of aspartic proteinase zymogens emanating from Scheme 1.

Figure 2 Time course of R_u, according to Equation (8). The set of values used for the equilibrium constants, rate constants and initial concentrations were the same as in Figure 1.

Figure 3 (A) Dependence of R_u,0 upon [I]₀, according to Equation (29), at a fixed [Z]₀-value (1 μM) and at different fixed values of [E]₀ (0, 10 nM, 100 nM and 1000 nM). (B) Dependence of R_u,0 upon [E]₀, according to Equation (29), at a fixed [Z]₀-value (1 μM) and at different fixed values of [I]₀ (0, 1 mM, 10 mM and 50 mM). Both in (A) and (B) the values of the equilibrium and rate constants were the same as in Figure 1.

Figure 4 (A) Dependence of R_u,∞ upon [Z]₀, according to Equation (30), at a fixed value of [I]₀ (0.1 mM) and different fixed values of [E]₀ (0.01 M, 0.1 M, 1 M and 10 M) (B)) Dependence of R_u,∞ upon [Z]₀, according to Equation (30), at a fixed value of [E]₀ (0.01 μM) and different fixed values of [I]₀ (0.1 mM, 10 mM, 50 mM and 100 mM). Both in (A) and (B) the values of the equilibrium and rate constants were the same as in Figure 1.