Final answer:
Enzyme affinities changes occur in or near the enzyme's active site due to alterations in amino acid sequences. These changes can impact the enzyme's specificity and catalytic action, which are determined by the precisely folded amino acid chains that form the active site. This specificity and function can also be influenced by post-translational modifications and the induced fit model.
Step-by-step explanation:
Changes in amino acid sequence that lead to alterations in enzyme affinities generally occur in or near the enzyme's active site. This is because the active site is the specific region within the enzyme where the substrate binds and undergoes a chemical reaction. Amino acid side chains within this region contribute to its unique chemical environment, which determines the enzyme's specificity and catalytic activity. When these amino acid sequences are modified, for example through genetic mutations or post-translational modifications (PTMs), the enzyme's affinity for its substrate can increase or decrease. This specificity arises because the sequences of amino acids fold into a precise three-dimensional shape, contributing to the creation of the active site with an environment perfectly apt for the catalysis of a particular reaction. Active sites often show a strong conservation of these amino acid sequences because they have evolved for optimal interaction with particular substrates. Nonetheless, the active site is not rigid; it is dynamic and can undergo conformational changes upon substrate binding, a phenomenon known as the induced fit model.