Implications for enzymic catalysis from free-energy reaction coordinate profiles

The constraints on the internal ground and transition states of enzyme-bound intermediates are mandated by the overall free-energy change in the direction of flux (Chin 1983; Stackhouse et al. 1985; Raines 1986) and the barrier for combination with reagent. Within these confines there are many solutions to transit the reaction coordinate. The path taken may reflect the function of the enzyme in question; particularly, whether in addition to catalysis there is a need to optimize reaction accuracy (Cramer and Freist 1987), to perform mechanochemical coupling (Jencks 1980), or to create metabolic control (Newsholme and Crabtree 1981; Koshland 1984).