Enzyme Kinetics and Reaction Rates

Enzyme kinetics examines the rates of enzyme-catalyzed reactions and how these rates change under different experimental conditions. It is fundamental to characterizing enzyme function, comparing catalytic efficiency, and evaluating the effects of inhibitors or activators.

The Michaelis–Menten model describes the relationship between substrate concentration and reaction velocity for many enzymes under appropriate conditions.

The equation is:

v = (Vmax × [S]) / (Km + [S])

Where:

• v is the initial reaction velocity.
• Vmax is the maximum reaction velocity under the specified conditions.
• [S] is the substrate concentration.
• Km is the Michaelis constant, corresponding to the substrate concentration at half of Vmax in the classical Michaelis–Menten model.

A lower Km often indicates that half-maximal velocity is reached at a lower substrate concentration, but Km is not universally equivalent to the binding affinity of an enzyme for its substrate.

The parameter kcat, known as the turnover number, describes how many substrate molecules one enzyme molecule can convert into product per unit of time when the enzyme is saturated with substrate. The ratio kcat/Km is commonly used to compare catalytic efficiency, particularly at low substrate concentrations.

Experimental kinetic analysis requires careful control of temperature, pH, reaction time, and substrate concentration to produce reliable and reproducible results.