What internal factor drives enzyme activity?

Enzyme activity is fundamentally influenced by the structure of the enzyme itself, notably its amino acid composition, which determines the enzyme's shape and active site configuration. The specific arrangement of amino acids in the protein structure is critical as it influences how the enzyme interacts with substrates. This relationship is often described by the "lock and key" model or the "induced fit" model, where the active site of the enzyme (which is shaped by its amino acids) must fit snugly with the substrate for the enzymatic reaction to occur efficiently.

Additionally, while factors such as pH, temperature, and substrate concentration can affect enzyme activity, they are external conditions rather than intrinsic characteristics of the enzyme itself. Changes in pH or temperature can lead to denaturation, altering enzyme function, while substrate concentration relates to the availability of reactants involved in the reaction. However, these factors do not change the fundamental design and capability of the enzyme that arises from its amino acid structure, which ultimately dictates how effectively it can catalyze reactions.