Enzyme kinetics

K_m, V_max, k_cat and catalytic efficiency from initial rates, plus K_i and the inhibition mechanism from a global fit, with the model choice justified by AICc.

Kinetics

How the analysis works

Rates are fitted directly by nonlinear least squares, never through a linearised plot, which distorts the errors. Three single-substrate models are compared:

v = V_max[S] / (K_m + [S])

plus substrate inhibition (K_si) and the Hill equation (h). The corrected Akaike criterion balances fit against complexity; Akaike weights give the relative support for each model.

Inhibition data are fitted globally. All inhibitor concentrations share one set of parameters, under four mechanisms:

v = V_max[S] / (K_m(1 + [I]/K_i) + [S](1 + [I]/αK_i))

Competitive (α → ∞), non-competitive (α = 1) and uncompetitive inhibition are special cases of this mixed model. k_cat = V_max/[E]_T, and its interval is propagated by the delta method. Validation report.