Enzyme Kinetics
The enzyme succinoxidase adds oxygen to succinate to give fumarate. The reaction follows Michaelis-Menton kinetics. The following rate data were determined for a solution in which the enzyme concentration is 10.0 uM:
[S](mM) ----------------- 0.33 10.00
vo (uM s-1) at 20 C ----- 0.50 1.17
vo (uM s-1) at 40 C ----- 2.41 5.65
(a) Determine Vmax and Km for the reaction at 20 C and 40 C.
For this question, I know that the Michaelis-Menton equation is:
vo = Vmax/1 + Km/[S]
- the equation then becomes:
vo = k2*[E]/ 1 + Km/[S]
We know what vo is for, [E],and [S], but k2 is not known. I'm not sure how to proceed with this question unless k2 is known.
(b) Compute the activation energy of this reaction (succinate + O2 --> fumarate).
For this question, would the equation K2/k1 = -Ea/R[1/T2 - 1/T1] be used. T2 and T1 is known, R is a constant (8.314) but how is k2 and k2 calculated. This part I do not understand.
(c) Will the activation energy be higher or lower in the absence of succinoxidase? Why?
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Another form of the Michaelis-Menten equation is: vo/Vmax = [S]/(Km + [S])
In the (a) part, since you know vo at two different substrate concentrations, you can substitute these into the MM equation. Then you ...
Solution Summary
This solution includes a rationale on how to answer all three parts of this question regarding enzyme kinetics. Based on what is known for parts a-c, guidance is given in terms of what equations to utilize to calculate certain values and how to interpret the question. All of this is done in about 250 words.
Understanding the Michaelis-Menten Equation, Enzyme Kinetics
For an enzyme which obeys Henri-Michaelis-Menten kinetics,
(1) At what substrate concentration will an enzyme characterized by a kcat of 30 s-1 and Km of 0.005 M show one quarter of its maximal rate?
(2) Calculate the fraction of Vmax that would be found when [S]=0.5 Km, [S]=3Km, and [S]=10Km
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