In the field of biochemistry, the specificity constant (also called kinetic efficiency or
), is a measure of how efficiently an enzyme converts substrates into products.
The higher the specificity constant, the more the enzyme "prefers" that substrate.
[1] The following equation, known as the Michaelis–Menten model, is used to describe the kinetics of enzymes: where E, S, ES, and P represent enzyme, substrate, enzyme–substrate complex, and product, respectively.
denote the rate constants for the "forward" binding and "reverse" unbinding of substrate, and for the "catalytic" conversion of substrate into product, respectively.
The Michaelis constant in turn is defined as follows: The Michaelis constant is equal to the substrate concentration at which the enzyme converts substrates into products at half its maximal rate and hence is related to the affinity of the substrate for the enzyme.
) is the rate of product formation when the enzyme is saturated with substrate and therefore reflects the enzyme's maximum rate.