Enzymes A and B catalyze different reactions but use the same reactant molecule
ID: 133706 • Letter: E
Question
Enzymes A and B catalyze different reactions but use the same reactant molecule as a substrate. The graph in Figure below presents the reaction rates observed when enzyme A and enzyme B are mixed together in a single test tube containing molecule X. What are the Vmax and the apparent Km values for each enzyme under these conditions? How might these values change for enzyme B if it were analyzed in the absence of enzyme A? Explain your answer (20 points). 4) 12.5 C o Enzyme B 10 - 7.5 Enzyme A 2.5 2.5 7.5 10 12.5 Concentration of X (uM)Explanation / Answer
Enzyme catalysis is carried out in a very discrete manner where reaction coordinates can be mathematically used to evaluate as well as predict the reaction kinetics further. Two most important parameters for such enzyme catalysis are Vmax and Km. Vmax refers to the maximum velocity of conversion of the substrate into product in the presence of enzyme. Km refers to the substrate concentration at which the reaction rate is half of the maximum.
According to the graphical representation, the reaction coordinates intersect each other at a point. It can be clearly seen from the graphical representation that the values of Vmax and Km are as follows:
Enzyme A: Vmax = nearly 6 units, Km = nearly 2.5 units
Enzyme B" Vmax = nearly 11 units, Km = nearly 3 units
This suggests that the reaction coordingates for these enzymes respresent to have nearly similar Km value. This is a kind of non-competetive inhibition.
Thus, the enzymes A and B tend to act as non-competetive inhibitors of each other and conduct the reaction under appropriate conditions. Thus, the reaction coordinates will remain similar in the absent of any of the enzymes A or B either since non-competetive inhibiton does not lead to any change in Km.
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