Enzyme activity is the measurable rate at which an enzyme catalyzes the conversion of substrate molecules into reaction products under specified experimental or cellular conditions. It represents the amount of chemical transformation occurring per unit time and depends on the concentration of catalytically competent enzyme, substrate availability, temperature, pH, ionic composition, cofactors, and the concentrations of products and regulatory molecules ^[1][2]. In kinetic analysis, activity is commonly quantified as an initial reaction velocity, determined while substrate depletion and product accumulation remain limited. For enzymes following a steady-state single-substrate mechanism, the relationship between initial velocity and substrate concentration is described by the Michaelis–Menten equation, whose parameters include the maximal velocity (V_max) and the Michaelis constant (K_M) ^[1][3]. Catalytic turnover is expressed by k_cat, the number of substrate molecules converted per active site per unit time under saturating substrate conditions ^[2]. Enzyme activity also encompasses changes in catalytic rate produced by reversible inhibitors, irreversible inactivators, allosteric effectors, covalent modification, and substrate or product binding ^[2][4].