Enzyme Kinetics Explorer

The Michaelis-Menten equation describes how the rate of an enzyme-catalyzed reaction depends on substrate concentration.

V_max is the maximum reaction velocity when all enzyme active sites are saturated with substrate. K_m (the Michaelis constant) is the substrate concentration at which the reaction rate is half of V_max. A lower K_m indicates higher substrate affinity.

The Lineweaver-Burk (double-reciprocal) plot linearizes the Michaelis-Menten equation, making it easier to determine K_m and V_max graphically.

The y-intercept gives 1/V_max, the slope gives K_m/V_max, and the x-intercept gives −1/K_m. This plot is especially useful for distinguishing between types of enzyme inhibition.

Competitive inhibition occurs when an inhibitor competes with substrate for the active site. This increases the apparent K_m while V_max remains unchanged. High substrate can overcome competitive inhibition.

Uncompetitive inhibition occurs when the inhibitor binds only the enzyme-substrate complex. Both apparent V_max and K_m decrease by the same factor.

Noncompetitive inhibition occurs when the inhibitor binds an allosteric site on either free enzyme or enzyme-substrate complex. Apparent V_max decreases while K_m stays the same.

Temperature affects enzyme activity in two ways. Moderate increases raise reaction rates because molecules have more kinetic energy. However, temperatures above the enzyme's optimal range cause denaturation, where the protein unfolds and loses its catalytic function. This creates an asymmetric bell-shaped activity curve.

pH affects the ionization state of amino acid residues in the active site. Each enzyme has an optimal pH range where the correct protonation states allow substrate binding and catalysis. Extreme pH values can denature the enzyme entirely. Most human enzymes function near pH 7.4, although exceptions exist (pepsin works best near pH 2).