Question

Enzymes. The enzyme tryptophan-tRNA synthetase binds to three different substrates, with the following Michaelis constants: ATP (KM = 50µM), tryptophan (KM = 0.5µM), and tRNA^Trp (KM = 1.5µM).

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A) Which substrate binds to the enzyme with highest affinity? _________________________

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B) When is the enzyme mostly saturated (i.e., mostly bound to all three substrates)?

[Circle one number (1 – 3).]

1) 1 µM ATP, 10 µM tryptophan, and 100 µM tRNA^Trp

2) 100 µM ATP, 1 µM tryptophan, and 10 µM tRNA^Trp

3) 10 µM ATP, 100 µM tryptophan, and 1 µM tRNA^Trp

Answer 1