# Solutions 9

- Page ID
- 47384

### Q9.1

Which of the following assumptions are made in Michaelis-Menten kinetics?

### Q9.2

What is \(V_{max}\)?

### Q9.3

What is \(K_m\)?

### Q9.4

How would the ten-fold decrease in enzyme concentration affect the observed \(K_m\)?

### Q9.5

You have isolated the enzyme larsenase from the rare parasite (*Facultium ignorantus*). This enzyme cleaves the first two numbers off of four digit dates. You flex your skills as an enzymologist and come up with the following graph of initial velocity as a function of substrate concentration:

a) From the graph, estimate \(K_m\).

b) What is the approximate value of \(V_{max}\)?

c) Is larsenase an allosteric enzyme? Explain.

### Q9.6

A specific enzyme-catalyzed reaction, \(V_{max} = 0.2 \; mol/sec\) and \(K_m = 5 \;mM\). Assume the enzyme shows standard Michaelis-Menten kinetics.

- What is the rate of the reaction when \([ S ] = 10\; mM\) ?\

\[V_{max} = .2 mol/s = 200 mmol/s\]

\[K_m = 5 mM\]

\[[S] = 10 mM\]

\[V_0 = \frac{V_{max}*[S]}{K_m + [S]} = 133.333 mmol/s = .133333 mol/s\]

b. Draw a Michaelis-Menten plot of the reaction kinetics, labeling the axes and giving values for the point where you can determine \(K_m\).

### Q9.7

The following data were obtained for an enzyme in the absence of an inhibitor and in the presence of an inhibitor.

\([S] \; (mm)\) | \(V_o \; \text{(Experiment one)}\) | \(V_o \; \text{(Experiment two)}\) |

1 | 8.6 | 24 |

2 | 16 | 40 |

4 | 28 | 58 |

10 | 42 | 70 |

Draw a Lineweaver-Burke plot of the reaction kinetics, labeling the axes and giving values for the two points where each line crosses the axes.

\[x_1 intercept = -\frac{.01019}{.03104} = -.3279\]

\[x_2 intercept = -\frac{.01141}{.10415} = -.1095\]

### Q9.8

What is the chemical basis of enzyme specificity?

The chemical basis of enzyme specificity is the nature and design of the enzyme active site.