For the enzyme succinoxidase, which adds oxygen to succinate to give fumarate, t
ID: 630030 • Letter: F
Question
For the enzyme succinoxidase, which adds oxygen to succinate to give fumarate, the following
rate data were determined for solutions in which the enzyme concentration is 10.0 uM.
a) What are the values of the Michaelis constants for this enzyme at the two temperatures?
b) What are the values of the rate constants kcat for this enzyme at the two temperatures?
c) What is the activation energy for the reaction of product formation?
d) Would you expect the activation energy for the reaction to be higher or lower for the same
reaction in the absence of the enzyme? Explain.
Explanation / Answer
FOLLOW THIS 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.