Suppose that your Ph.D. mentor asks you to compare the kinetic behavior of the two recently discovered peptidase isozymes PepA and PepB. Your mentor's initial studies identified a pentapeptide substrate called Tide5 that appeared to be able to distinguish the kinetic behaviors of PepA and PepB. All they had time to tell you was this: At low Tide5 concentration, the ?o (initial velocity) of PepA was greater than PepB, but at high Tide5 concentration, the reverse was true. Before you start your kinetic assays, you decide it would be wise to ponder this small bit of information. You have no numbers to work with, but does it tell you something about the relative values of ?m and ?max for PepA and PepB? Select the statements that are consistent with the information that you were given.

You design an enzyme assay and choose a substrate concentration equal to the Km of the enzymatic reaction. You measure the rate of the reaction at this substrate concentration to be 75.0 μmol/min. Calculate the Vmax of this reaction in μmol/min. Express your answer with one decimal place.  Your previous attempt suffered from low signal-to-noise ratio when you used a substrate concentration equal to the Km. So you decide to increase the substrate concentration to 0.45 mM. You remeasure the rate of the reaction at this new substrate concentration and find it to be 135.0 μmol/min. Using the same Vmax value found above, calculate the Km value of this enzymatic reaction. Express your answer in μM with one decimal place.  Considering the previous two questions, what would be the rate of the reaction at a substrate concentration of 0.01 mM? Express your answer in μmol/min with one decimal place.