The correct answer is: C) an enzyme with more than one subunit
An allosteric regulation of an enzyme refers to the binding of effector molecules at a site other than the enzyme's active site. That site is called the allosteric site or regulatory site. When the regulator (effector molecule) binds enzyme usually goes through conformational change. When the activity of the enzyme is reduced, we call effector molecule inhibitor, otherwise it is activator.
Allosteric enzymes usually have multiple active sites located on different protein subunits, but when one effector molecule binds all sites on different subunits are changed .
