What order of reaction depends solely on enzyme concentration?

The order of reaction that depends solely on enzyme concentration is zero order. In a zero-order reaction, the rate of the reaction remains constant and is independent of the substrate concentration. This occurs when the enzyme is saturated with substrate, meaning that all active sites of the enzyme molecules are occupied, and the reaction rate reaches a maximum velocity (Vmax).

In this state, even if substrate concentration increases, it does not affect the rate of reaction because the enzyme is operating at its maximum capacity. The reaction rate is solely dependent on the concentration of the enzyme itself.

This concept is important in enzyme kinetics, particularly in the Michaelis-Menten model where, at high substrate concentrations, the reaction follows zero-order kinetics. Understanding this principle helps in laboratory settings to determine enzyme activity and optimize conditions for various biochemical reactions.