Question

Chymotrypsin serves as a catalyst in the "Hydrolysis" of pepdite bonds - found in carboxylic groups of amino acids, which consist of aromatic pedand groups and large hydrophobic groups. Chymotrypsin is also known to serve as a catalyst in the Hydrolysis of "ester - and amide bonds" , found in hydrophobic groups. 1. Would you expect the KM of the reactions of Chymotrypsin with the different substrates to have the same value ? explain your reasoning. 2. Would you expect the Vmax of the reactions of Chymotrypsin with the different substrates to have the same value ? explain your reasoning. 3. Would you expect the " pH-dependence " of the "hydrolysis - reactions" of the different substrates to be the same for all substrates ? explain your reasoning.

Answer 1

1. The K_m of the reactions of Chymotrypsin with the different substrates will have different values. That's because the active site best accommodates substrates with a bulky hydrophobic or aromatic residue contributing carbonyl group to peptide bond to be hydrolyzed.Thus, with different incoming substrates, the value of K_m will be different.

Low K_m values mean high binding affinity and high K_m value mean low binding affinity.

2. K_m is the substrate concentration that is required for the reaction to occur at 1/2 V_max. In other words, it is how much substrate is needed for the reaction to occur at 1/2 its max possible rate. Obviously V_max is the maximum rate that the reaction can proceed at. Thus, V_max also changes with different substrates.

3. pH dependence of the hydrolysis doesn't matter as Km is independent of enzyme concentration