2.00 24. Explain the energetic benefits of making the enzyme active site complementary to the transition state rather than to the substrate conformation. Also explain how multiple weak interactions contribute to enzyme action. (In other words, how do these weak interactions between the enzyme and the transition state lower the activation energy?) 25. T/F. The pk's of titratable groups of amino acids remain constant irrespective of chemical or sequence environment 26. Look for the slide in Lecture 6 titled "Binding/Entropy Reduction". Using the images in this screen, explain how an enzyme further lowers the activation energy by reducing entropy 27. In the progress curve to the right one observes the so called "burst phase kinetics" that illustrate the action of proteases and other enzymes. Explain the shape of the curve. In other words, why would there appear to be an initial burst at the onset of the enzymatic reaction? 28. How do serine proteases interact with their peptide/protein ligands in a sequence-specific way? In the peptide below, identify the peptide bonds that will be cut by the three different kinds of serine proteases. (EXTRA CREDIT: identify the sequence of the peptide and give an approximate pH of the solution) p-Nitrophenol (mol/mol of enzymel 1.0 Time (min) NH OH 29. Hypothesize what would happen if there's a mutation in the oxyanion hole of serine proteases for instance, if the Gly193 is mutated into a Pro, a Glu, or a Trp. 30. Describe the roles of each residue in the so-called "catalytic triad" of serine proteases. 31. The so-called "tetrahedral intermediate" (pictured on the right) occurs during the transition state of serine protease action. Is this a stable or an unstable structure? Explain. Tetrahedral intermediate