Localization of various metabolic pathways in the membranous compartments regulate metabolic processes. This is the mechanism in which regulation of enzyme activity is achieved by physical separation and localization of specific groups of enzymes in membrane bound compartments in the all. Different metabolic pathways take place in these different intracellular locations which are called organelles. For example, in both animal and plants, process of respiration take place in two parts Glycolysis and Krebcycle. Enzymes involved in Krebs cycle are physically separated from those of glycolysis. Krebs cycle is confined with in the mitochondria and glycolysis takes place in the cytosol. Prokaryotic cell contain no compartments, yet there is some degree of segregation of certain enzymes in bacteria, e.g. the enzymes participating in the biosynthesis of phospholipids are located in the cell membrane.
Localization of different metabolic processes in Cytosol or in the organelle enables the regulation of these processes independent of processes proceeding elsewhere. But at the same time translocation of metabolities across the membranes of the compartment is achieved via shuttle mechanism which converts the metabolic into permeable form. So that it can move cross the membrane and transported out. Once the metabolic is outside the compartment, it is converted back to its original form. Such type of inter conversion is carried out with the help of enzyme catalysis. As these enzymes are physically separated by the compartmental barrier, they are regulated independently. Interconversions of metabolites in mitochondrial and cytosolic form during Krebs’s cycle and glycolysis is example of such type of inter conversion.