Multiple Choice
Which of the following would be altered on a Lineweaver-Burk plot in the presence of a competitive inhibitor?
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7. Enzyme Inhibition and Regulation
Competitive Inhibition
Multiple Choice
N-hydroxy-L-arginine (an intermediate in nitric oxide biosynthesis) can bind to the active site of arginase making its manganese reactive metal center unavailable for catalysis. How would an increased concentration of this intermediate be expected to affect the kinetic parameters of this enzyme?
A
The apparent Vmax will decrease.
B
The apparent Km for arginine will decrease.
C
The apparent Vmax will increase.
D
The apparent Km for arginine will increase.
Verified step by step guidance1
Understand the role of N-hydroxy-L-arginine: It acts as a competitive inhibitor by binding to the active site of arginase, preventing the substrate (arginine) from binding.
Recall the effect of competitive inhibition on enzyme kinetics: Competitive inhibitors increase the apparent Km (Michaelis constant) because a higher concentration of substrate is needed to reach half of the Vmax.
Note that Vmax remains unchanged in competitive inhibition: Since the inhibitor can be outcompeted by a high concentration of substrate, the maximum reaction velocity (Vmax) is not affected.
Analyze the given options: The apparent Vmax will not decrease or increase because competitive inhibition does not affect Vmax. The apparent Km for arginine will increase due to the need for more substrate to achieve the same reaction rate.
Conclude that the correct effect of increased N-hydroxy-L-arginine concentration is an increase in the apparent Km for arginine, consistent with competitive inhibition.
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