Dissociation constant

The affinity is a measure of the biochemistry of the binding strength between the binding partners for protein -ligand interactions ( also known binding constant ) The higher the affinity, the greater the association constant, Ka.

Properties

Commonly, the reciprocal measure, the dissociation constant, Kd is today, however, instead of the association constant used: the higher the affinity of a protein to its ligand, the lower the dissociation constant of the complex. The example of the formation / decay of an enzyme- substrate complex, [ES ]

The definitions in the mass action law and kinetic constants are listed ( rate constant k) here:

In the enzyme kinetics is sometimes Km, the Michaelis constant, as a measure of the affinity of an enzyme to its substrate. This has a certain justification, theoretically the dissociation constant of the ES complex Kd and the Michaelis constant, however, are to be strictly distinguished in practice. The Michaelis constant depends by Briggs and Haldane and the AC number k2 and is calculated as follows:

A conclusion of Km on Kd is only possible if. This assumption is not appropriate in every case, but was originally made ​​by Leonor Michaelis and Maud Menten to derive the Michaelis -Menten equation.

The affinity can be determined by ligand binding assays.