Solution:

A heterotropic allosteric modulator is a regulatory molecule that is not the enzyme’s substrate. It may be either an activator or an inhibitor of the enzyme. For example, H+, CO2, and 2,3-bisphosphoglycerate are heterotropic allosteric modulators of hemoglobin. Once again, in IMP/GMP specific 5′ nucleotidase, binding of GTP molecule at the dimer interface in the tetrameric enzyme leads to increased affinity for substrate GMP at the active site indicating towards K-type heterotropic allosteric activation.

As has been amply highlighted above, some allosteric proteins can be regulated by both their substrates and other molecules. Such proteins are capable of both homotropic and heterotropic interactions.