Question

The following rate constants were determined for a Michaelis-type enzyme: k1 = 2.5 x 10^9 M-1 s -1 , k-1 = 5.0 x 10^3 s -1 , and k2 = 5.0 x 10^4 s -1 . a. What are the values of Km, Ks, and kcat for this enzyme? Is this a rapid equilibrium enzyme or does it just follow steady state kinetics? Explain the basis for your answer. b. What substrate concentration is needed to achieve half maximal velocity? Explain the basis for your answer. c. If the substrate concentration from part b is increased 5-fold, how many fold will the initial velocity increase? d. If the enzyme is present at 10 pM in a 1-ml reaction mixture and has one active site per enzyme, what is the Vmax? e. Assume this enzyme is a serine protease. If 2 nmol of the irreversible protease inhibitor PMSF is added to the reaction mixture in part d and is completely reacted with the enzyme prior to the addition of substrate, what will be the resultant Km and Vmax values?

Answer 1