Amino Acids & Proteins MCAT Practice Question
A biochemist characterizes a mutant enzyme and finds that substituting leucine with aspartate at a critical position reduces enzyme activity to 5% of wild-type levels. The enzyme's Michaelis constant (Km) increases dramatically while kcat remains relatively unchanged. Which structural change most likely explains these kinetic observations?
Answer choices
- ADecreased substrate binding affinity due to loss of hydrophobic interactions in the substrate binding pocketCorrect answer
- BImpaired catalytic efficiency due to reduced cofactor binding capacity
- CIncreased allosteric inhibition by the substrate itself
- DEnhanced proteolytic degradation of the mutant enzyme in cells
- EDisruption of the enzyme's oligomeric quaternary structure
- FAltered substrate specificity leading to preferential binding of alternative substrates with lower catalytic rates
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