Enzymes are catalysts that increase the rate of reactions by pulling two substrates together.   lowering the energy of activation.   binding to a substrate and releasing protons.   binding to a substrate and producing energy.

Catalysts speed up the chemical reaction without being changed themselves. All living organisms prepare biological catalysts called enzymes. Enzymes are globular proteins that act as biocatalysts for many chemical reactions. In the absence of enzymes, many chemical processes occur at a very slow rate in living organisms. By preparing enzymes, cells can regulate what chemical reactions happen in their cytoplasm.