This lecture covers the catalytic strategies employed by enzymes, focusing on proteases and carbonic anhydrase. Topics include the cleavage of peptide bonds, stabilization of transition states, covalent catalysis, enzyme inhibition, and the specificity of serine proteases. The mechanisms of catalysis, including the role of zinc ions and water molecules, are discussed. Additionally, the lecture explores the catalytic mechanisms of restriction enzymes and the impact of inhibitors on enzyme kinetics.