ordered on-random off mechanism

or·dered on-·ran·dom off mech·a·nism

a scheme for substrate binding and product release for multisubstrate enzymes; for a two-substrate two-product enzyme with this mechanism, the reactants must bind to the enzyme in a distinct order; however, after the products have been formed, they may dissociate from the enzyme in either order. It has been suggested that hepatic pyruvate kinase has such a mechanism. The random on-ordered off mechanism is simply the reverse of this mechanism.