MichaelisMentenKinetik

Michaelis-Menten kinetics, or Michaelis-Menten kinetics, is a model of enzyme-catalyzed reactions that describes how reaction velocity depends on substrate concentration. It assumes a simple mechanism in which an enzyme E binds substrate S to form an enzyme-substrate complex ES, which then converts to product P and regenerates free enzyme. The typical reaction is E + S ⇌ ES → E + P.

Under the steady-state approximation, the concentration of ES remains constant during the initial phase of the reaction. The resulting rate equation is v = (Vmax [S]) / (Km + [S]), where v is the initial velocity, [S] is the substrate concentration, Vmax is the maximum velocity at saturating substrate, and Km is the Michaelis constant, the substrate concentration at which v equals half of Vmax. Vmax is proportional to the total enzyme concentration and reflects turnover number when all enzyme molecules are saturated. Km is an apparent affinity measure; a lower Km indicates higher affinity between enzyme and substrate, though it depends on the kinetic rates of ES formation and breakdown.

The model is widely used to estimate kinetic parameters by fitting experimental data to the equation and to compare enzymes. It is most applicable under conditions where product inhibition and reverse reactions are negligible, at constant temperature and pH, and for initial-rate measurements. While foundational, Michaelis-Menten kinetics is a simplification; many enzymes exhibit substrate inhibition, multiple substrates, allosteric effects, or more complex mechanisms that require advanced models. The concept remains foundational in biochemistry and enzymology.