ABSTRACT
Feedback regulation In biological systems, the rates of many enzymes are altered by the presence of other molecules such as activators and inhibitors (collectively known as effectors). A common theme in the control of metabolic pathways is when an enzyme early on in the pathway is inhibited by an end-product of the metabolic pathway in which it is involved. This is called feedback inhibition and often takes place at the committed step in the pathway (conversion of A to B in Figure 1a). The committed step is the first step to produce an intermediate which is unique to the pathway in question, and therefore normally commits the metabolite to further metabolism along that pathway. Control of the enzyme that carries out the committed step of a metabolic pathway conserves the metabolic energy supply of the organism, and prevents the build-up of large quantities of unwanted metabolic intermediates further along the pathway. Such feedback inhibition is seen, for example, in the pathways involved in the biosynthesis of amino acids (Section M2).
