Subunit neighbor interactions in enzyme kinetics: half-of-the-sites reactivity in a dimer.
We consider an isologous enzyme dimer in which the subunits, if operating independently, would obey Michaelis-Menten kinetics. However, because of neighbor interactions, the rate constants of the kinetic cycle in either subunit depend on the state (E or ES) of the other subunit. The steady-state behavior of this dimer system, with interactions, is investigated. In what is probably the most important special case, ES x ES is destabilized considerably by the neighbor interaction compared to E x ES. This leads to half-of-the-sites reactivity (one subunit is in state ES; the other subunit cycles between E and ES), negative cooperativity, and a considerable enhancement of enzyme activity relative to the activity of independent subunits.
D000494:Allosteric Regulation; D001665:Binding Sites; D004798:Enzymes / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008962:Models, Theoretical; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D004798:Enzymes; D046911:Macromolecular Substances