Biology – Mode of action of enzymes | e-Consult

The function of an enzyme is directly related to its three-dimensional structure. The specific arrangement of amino acids in the polypeptide chain determines the shape of the enzyme, including the shape and chemical properties of the active site. The active site is precisely shaped to bind to a specific substrate, forming the enzyme-substrate complex.

Tertiary and quaternary structure are crucial for maintaining the active site's shape. These structures are maintained by various bonds (hydrogen, ionic, disulfide). Changes to these structures, such as those caused by heat, pH changes, or denaturation agents (e.g., alcohol or detergents), can disrupt the enzyme's 3D conformation. This disruption can lead to unfolding of the protein and a loss of the active site's specific shape. As a result, the enzyme loses its ability to bind to the substrate and catalyze the reaction. This is known as denaturation.

Enzyme inhibition often involves binding of a molecule (an inhibitor) to the enzyme, which can alter its structure and affect its activity. Inhibitors can be competitive (binding to the active site, preventing substrate binding) or non-competitive (binding to a different site on the enzyme, causing a conformational change that affects the active site). The degree of inhibition depends on the inhibitor's affinity for the enzyme and the concentration of the inhibitor.