You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. you notice it has two binding sites. one of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. what do these findings tell you about the mechanism of this protein?

a) it is probably a structural protein that is involved in cell-to-cell adhesion.
b) it is probably an enzyme that works through allosteric regulation.
c) it is probably an enzyme that works through competitive inhibition.
d) it is probably a cell membrane transport protein–like an ion channel.

The correct answer is: B) It is probably an enzyme that works through allosteric regulation.

An allosteric regulation of an enzyme refers to the binding of effector molecules at a site other than the enzyme's active site. So, in the example above, larger binding site is for the substrate, while the smaller one is for the effector molecule (regulator).  

The site for the binding of regulator 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 .