Biochemistry
Biochemistry
9th Edition
ISBN: 9781319114671
Author: Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher: W. H. Freeman
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**Title: Enzyme Kinetics Analysis of Wild-Type and Mutant Enzymes**

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**Graph Explanation:**

The provided graph is a Michaelis-Menten plot illustrating the enzymatic activity of a wild-type (WT) enzyme and a mutant (V105A) enzyme, both isolated from the bacterium *Staphylococcus aureus*. The plot shows enzyme velocity (\(v\), in \(\mu\)mol/s/mg) versus substrate concentration (\([s]\), in mM).

- **Curve for WT (black circles):** The wild-type enzyme shows a gradual increase in reaction velocity as substrate concentration increases. The curve appears to begin leveling off around a velocity of 0.5 \(\mu\)mol/s/mg.
  
- **Curve for V105A (red circles):** The mutant enzyme demonstrates a rapid increase in reaction velocity, leveling off at a higher maximum velocity compared to the WT, around 1.25 \(\mu\)mol/s/mg.

Both curves highlight the differences in kinetic behaviors between the wild-type and mutant enzymes.

---

**Questions and Discussion:**

**(a) Estimate the \(K_m\) and \(V_{max}\) for the wild-type and mutant enzyme from the graph.**

- **Wild-Type (WT):**
  - \(V_{max}\) is approximately 0.5 \(\mu\)mol/s/mg.
  - \(K_m\) is roughly where the velocity is half of \(V_{max}\), estimated around 250 mM.

- **Mutant (V105A):**
  - \(V_{max}\) is approximately 1.25 \(\mu\)mol/s/mg.
  - \(K_m\) is estimated around 100 mM, where the velocity reaches half of \(V_{max}\).

**(b) Calculate the \(K_{cat}\) and \(K_{cat}/K_m\) for the wild-type and mutant enzyme based on your estimated values in (a) if the total enzyme concentration is 0.5 \(\mu\mol\)/mg.**

- **Wild-Type (WT):**
  - \(K_{cat} = \frac{V_{max}}{[\text{Enzyme}]} = \frac{0.5}{0.5} = 1 \, \text{s}^{-1}\)
  - \(K_{cat
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Transcribed Image Text:**Title: Enzyme Kinetics Analysis of Wild-Type and Mutant Enzymes** --- **Graph Explanation:** The provided graph is a Michaelis-Menten plot illustrating the enzymatic activity of a wild-type (WT) enzyme and a mutant (V105A) enzyme, both isolated from the bacterium *Staphylococcus aureus*. The plot shows enzyme velocity (\(v\), in \(\mu\)mol/s/mg) versus substrate concentration (\([s]\), in mM). - **Curve for WT (black circles):** The wild-type enzyme shows a gradual increase in reaction velocity as substrate concentration increases. The curve appears to begin leveling off around a velocity of 0.5 \(\mu\)mol/s/mg. - **Curve for V105A (red circles):** The mutant enzyme demonstrates a rapid increase in reaction velocity, leveling off at a higher maximum velocity compared to the WT, around 1.25 \(\mu\)mol/s/mg. Both curves highlight the differences in kinetic behaviors between the wild-type and mutant enzymes. --- **Questions and Discussion:** **(a) Estimate the \(K_m\) and \(V_{max}\) for the wild-type and mutant enzyme from the graph.** - **Wild-Type (WT):** - \(V_{max}\) is approximately 0.5 \(\mu\)mol/s/mg. - \(K_m\) is roughly where the velocity is half of \(V_{max}\), estimated around 250 mM. - **Mutant (V105A):** - \(V_{max}\) is approximately 1.25 \(\mu\)mol/s/mg. - \(K_m\) is estimated around 100 mM, where the velocity reaches half of \(V_{max}\). **(b) Calculate the \(K_{cat}\) and \(K_{cat}/K_m\) for the wild-type and mutant enzyme based on your estimated values in (a) if the total enzyme concentration is 0.5 \(\mu\mol\)/mg.** - **Wild-Type (WT):** - \(K_{cat} = \frac{V_{max}}{[\text{Enzyme}]} = \frac{0.5}{0.5} = 1 \, \text{s}^{-1}\) - \(K_{cat
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