Intramolecular signal transmission in regulatory enzymes: Are polarons involved?

The regulatory enzyme Aspartate transcarbamylase (ATCase), the first enzyme of the pyrimidine pathway, catalyses the carbamylation of the amino group of aspartate by carbamylphosphate. This reaction is feedback inhibited by the end products of the pathway, CTP and UTP. In contrast, it is stimulated by ATP which binds to a regulatory site distant from the catalytic site by 60 Å. The structural features specifically involved in this effect of ATP delineate a path for the transmission of this regulatory signal over that distance. The nature of these structural features suggests the possible implication of polarons in the transmission of a long-distance electromechanical signal.