regulatory subunit

A regulatory subunit is a component of a larger protein complex, such as an enzyme, that controls its activity. Think of it as a "governor," binding to the active part of the enzyme and either activating or inhibiting its function. The regulatory subunit doesn’t perform the main action itself but influences when or how the enzyme works, often in response to signals like hormones or cellular conditions. This regulation helps ensure the enzyme operates only when needed, maintaining proper cellular function and balance.