Final answer:
The enzyme's ability to bind only with specific substrates is referred to as its specificity, resembling a 'lock and key' mechanism.
Step-by-step explanation:
The characteristic of an enzyme to react with only limited, selected substrates is known as the enzyme's specificity. Enzymes are highly specific due to the unique combination of amino acid residues within their active sites, which create a specific chemical environment suitable for the binding of their designated substrates, ensuring that the enzyme only catalyzes specific biochemical reactions.
This specificity is often compared to a 'lock and key' mechanism where only the right key (substrate) fits into the lock (enzyme's active site). Enzymes undergo a process called induced fit, where they slightly change their structure to achieve the best match between the enzyme's active site and the transition state of the substrates. Therefore, this selective binding is essential for the enzyme's function to lower the activation energy and speed up chemical reactions.