Enzymes A and B catalyze different reactions but use the same reactant molecule

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 underthese 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 10- C o Enzyme B 7.5 Enzyme A 2.5 2.5 7.5 10 12.5 Concentration of X (uM)

Explanation / Answer

The Km value is substrate concentration at half maximal velocity.

For enzyme A, Vmax is 6 uM/min and Km is 1.25 uM. For enzyme B, Vmax is 10 uM/min and Km is 3 uM.

The enzymes A and B are in competitive inhibition. So, if the enzyme A is absent, the Vmax value of enzyme B remains unchanged but Km value increases.

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