Goldbeter–Koshland module

In systems biology and biochemistry, a Goldbeter–Koshland module (also known as a Goldbeter–Koshland switch or a reversible covalent modification cycle) is a mathematical model that describes how a biological system can produce a sharp, switch-like response from a gradual chemical signal. Proposed by biochemists Albert Goldbeter and Daniel E. Koshland Jr. in 1981, the module represents a two-state biochemical system in which a target protein is continuously converted between an active and an inactive form by two opposing enzymes. This dynamic is commonly illustrated by a kinase adding a phosphate group to a protein, while a phosphatase removes it. The model mathematically demonstrates “ultrasensitivity,”