Specificity Constant

Use the data in the chart below to provide answers to the following problems:

A) List the substrates from most preferred to least preferred under physiological conditions. 

            a) B, A, C.         b) C, B, A.         c) B, C, A.         d) A, C, B.

B) List the substrates from most preferred to least preferred under saturating [S].

            a) B, A, C.         b) C, B, A.         c) B, C, A.         d) A, C, B.

Practice: Which of the following options is correct concerning the turnover number (k _cat) and the specificity constant?

Practice: Use the Lineweaver-Burk plot to help you calculate the V_max, k_cat, K_m and specificity constant for the enzyme.

Assume the [E]_T = 2.9 nM. Hint: Pay close attention to units. 

V_max = ___________. 

k_cat = ___________. 

K_m = ___________.

k_cat / K_m = ___________.

Practice: Explain the steps you could take to accurately find the K _m, V_max, and specificity constant for an enzyme from the following kinetic data, assuming the experiments were all done with [E]_T = 0.1 mM.

Step #1: ___________________________________________

Step #2: ___________________________________________

Step #3: ___________________________________________

Step #4: ___________________________________________

Step #5: ___________________________________________

Practice: The specificity constant is obtained at low [S] via variable substitution into the Michaelis-Menten equation (V_max = k_cat[E]_T). Considering this about the MM-equation, what is the relationship between changes in [S] & V₀ when the [S] is super small and well below the K_m?