Enzyme Inhibition Mechanisms Quiz

Enzyme Inhibition

• Reversible Noncompetitive Inhibition: a molecule decreases enzyme activity by binding to a site on an enzyme other than the active site.
• Irreversible Inhibition: a molecule inactivates an enzyme by forming a strong covalent bond to an amino acid side-chain group at the enzyme's active site, permanently deactivating the enzyme.

Types of Inhibitors

• Inhibitors that decrease enzyme activity by binding to a site on the enzyme other than the active site are associated with Reversible Noncompetitive Inhibition.
• Inhibitors that inactivate enzymes by forming a strong covalent bond at the enzyme active site are associated with Irreversible Inhibition.
• Inhibitors that have a shape and charge distribution similar to that of the enzyme's normal substrate are associated with Reversible Competitive Inhibition.
• Inhibitors whose effect can be reduced by increasing the concentration of normal substrate present are associated with Reversible Competitive Inhibition.

Regulation of Enzymes

• Regulation of enzyme activity is important because a cell that continually produces large amounts of an enzyme for which substrate concentration is always very low is wasting energy.
• The production of the enzyme needs to be "turned off" when the product of an enzyme-catalyzed reaction is present in plentiful amounts in a cell.
• Enzyme concentration affects reaction rate, with a higher enzyme concentration resulting in a greater reaction rate.

Factors that Influence Enzyme Activity

• Increasing the substrate concentration increases the rate of a reaction.
• Increasing the enzyme concentration increases the rate of a reaction.
• Increasing the temperature from its optimum value to a value 10°C higher than this value decreases the rate of a reaction.
• Lowering the pH from the optimum value of 5.0 to a value of 3.0 decreases the rate of a reaction.

Allosteric Enzymes

• Allosteric enzymes are responsible for regulating many cellular processes.
• They have a quaternary structure, consisting of two or more protein chains.
• They have two kinds of binding sites: those for substrate and those for regulators.
• Active and regulatory binding sites are distinct from each other in both location and shape.
• Binding of a molecule at the regulatory site causes changes in the overall 3D structure of the enzyme, including structural changes at the active site.

Mechanisms of Regulating Enzymes

• Feedback Control: a process in which activation or inhibition of the first reaction in a reaction sequence is controlled by a product of the reaction sequence.