2) The initial rate for an enzyme-catalyzed reaction has been determined at a nu

Question

2) The initial rate for an enzyme-catalyzed reaction has been determined at a number of substrate concentrations. Data are given below.

[S](M)_________ vo(Mmin-1)

5 _________________20

10_________________ 39

20_________________ 67

50_________________ 105

100________________ 118

200________________ 137

500________________ 148

a) Estimate Vmax and Km from a direct (Michaelis-Menton) graph of vo vs [S]

b) Use a Lineweaver-Burk plot to analyze the same data. What are the values of Vmax and Km?

c) If the total enzyme concentration is 50 pM, what is kcat?

d) Calculate kcat/Km for this enzyme. Is the enzyme an efficient enzyme?

Explanation / Answer

a) plot Vo vs [S], from the graph: Vmax = 160 uMmin-1, Km = 30 uM

b) using Lineweaver-Burk plot, Vmax = 181.82 uMmin-1, Km = 39.07 uM

c) Kcat = Vmax/ total concentration = 181.82 uMmin-1/0.00005 uM = 3.62E6

d) Kcat/Km = 3.62E6/39.07 uM = 9.27E4, thus the enzyme is efiicient

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