Regulation of Enzymes

• Enzyme activity is regulated to reflect the physiological state of the organism.
• The rate of an enzyme-catalyzed reaction is dependent on substrate concentration and can be represented mathematically by the Michaelis-Menten equation.
• Allosteric activators or inhibitors are compounds that bind at sites other than the active catalytic site and regulate the enzyme through conformational changes affecting the catalytic site.
• A number of different mechanisms are available to regulate enzyme activity. These include:
• Feedback inhibition, which often occurs at the first committed step of a metabolic pathway
• Covalent modification of an amino acid residue (or residues) within the protein
• Interactions with modulator proteins, which when bound to the enzyme, alter the conformation of the enzyme, and hence activity
  Altering the primary structure of the protein via proteolysis
• Increasing or decreasing the amount of enzyme available in the cell via alterations in the rate of synthesis of degradation of the enzyme
• Metabolic pathways are frequently regulated at the slowest, or rate-limiting, step of the pathway.