Direction: An enzyme (24000 Da) undergoes first-order deactivation kinetics while catalyzing a reaction according to Michaelis-Menten kinetics (K_m= 10^–4 M). The enzyme has a turnover number if 10⁴ molecules substrate/min-(molecule enzyme) and a deactivation constant (k_d) of 0.1 min^–1 at the reaction conditions. The reaction mixture initially contains 0.6 mg/l of active enzyme and 0.02 M of the substrate.