How does an enzyme make a metabolic reaction run much faster?

Core Concept

Every reaction must pass through a transition state in which bonds are partially broken and formed, and the energy needed to reach that state controls the reaction rate. An enzyme positions substrate groups and stabilizes this strained arrangement, lowering the barrier so a far larger fraction of collisions succeeds. The enzyme is not consumed, supplies no energy of its own, and cannot move the equilibrium, which is fixed by the thermodynamics of substrates and products.