Open AccessSubunit neighbor interactions in enzyme kinetics: half-of-the-sites reactivity in a dimer.
Author(s) -
Terrell L. Hill,
Alexander Levitzki
Publication year - 1980
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.77.10.5741
Subject(s) - cooperativity , dimer , protein subunit , kinetics , chemistry , enzyme , reactivity (psychology) , cooperative binding , enzyme kinetics , biophysics , stereochemistry , biochemistry , biology , active site , physics , alternative medicine , organic chemistry , pathology , quantum mechanics , gene , medicine
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.