Enzymes as Catalysts

• Enzymes are proteins that act as catalysts—molecules that can accelerate the rate of a reaction.
• Enzymes are specific for various substrates because of the selective nature of the binding sites on the enzyme.
• The catalytic (active) site is the portion of the enzyme molecule at which the reaction occurs.
• Enzymes accelerate reaction rates by decreasing the amount of energy required to reach a high-energy intermediate stage of the reaction, known as the transition state complex. This is referred to as lowering the energy of activation.
• Enzymes utilize functional groups at the active site, provided by coenzymes, metals, or amino acid residues, to perform catalysis.
• Enzymes utilize general acid-base catalysis, formation of covalent intermediates, and transition state stabilization as various mechanisms to accelerate reaction rates.
• Many drugs and toxins act by inhibiting enzymes.
• Enzymes can be regulated to control reaction rates through a variety of mechanisms.