Gateway Technical College BIO 806-177 Lecture 9 : Enzyme Mechanisms 1)Which of the following is NOT a method that an enzyme would use to achieve rate enhancement in a reaction S ? P? Introduce favorable hydrogen bonds to the substrate S Introduce favorable hydrogen bonds to the transition state of the reaction Providing a residue to serve as a general base for the reaction Coordinate a metal ion that acts as a general acid for the reaction When chymotrypsin cleaves a peptide bond, which of the following best describes the role of Ser 195? Acting as a general base to deprotonate a water molecule Acting as a nucleophile to attack the amide carbonyl of the peptide Stabilizing an intermediate state by forming a covalent bond to the peptide residue C-terminal to the scissile bond Stabilizing the deprotonated His 57 When chymotrypsin cleaves a peptide bond, which of the following best describes the role of His 57? Acting as a nucleophile to attack the amide carbonyl of the peptide Stabilizing Asp 102 Contributing a backbone amide proton to form the oxyanion hole stabilizing the transition state Acting as a general base to deprotonate a water molecule When chymotrypsin cleaves a peptide bond, which of the following best describes the role of Asp 102? Acting as a general base to deprotonate a water molecule Stabilizing the protonated His 57 Acting as a nucleophile to attack the amide carbonyl of the peptide Contributing a backbone amide proton to form the oxyanion hole stabilizing the transition state Which of the following is NOT a role metal may play in enzyme catalysis? Binding a substrate Oxidation and reduction Binding water molecules Coordination of nonpolar side chains