Vmax

Vmax (or V_max) is a term used in enzyme kinetics to denote the maximum rate of an enzyme-catalyzed reaction. It is the rate of the reaction when the enzyme is saturated with the substrate. The term Vmax is derived from the Michaelis-Menten kinetics, which is a model for the kinetics of a simple enzyme-catalyzed reaction.

Overview

Vmax is a measure of the amount of product that can be formed by an enzyme in a given amount of time under saturating conditions of substrate concentration. It is a theoretical maximum rate of reaction, which can only be approached under ideal conditions. The actual rate of an enzyme-catalyzed reaction is usually less than the Vmax because the substrate concentration is not usually high enough to saturate the enzyme.

Calculation

Vmax can be calculated from the Michaelis constant (Km) and the enzyme concentration ([E]) using the following equation:

Vmax = kcat[E]

where kcat is the turnover number of the enzyme, which is the maximum number of substrate molecules an enzyme molecule can convert to product per unit time.

Factors affecting Vmax

Vmax is affected by several factors including the enzyme concentration, the substrate concentration, the temperature, the pH, and the presence of any inhibitors or activators.

See also

• Enzyme kinetics
• Michaelis-Menten kinetics
• Turnover number
• Substrate (chemistry)