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Chapter 12: Q23P (page 399)

You are trying to determine the KM for an enzyme. Due to a labmishap, you have only two usable data points:

Substrate concentration (μM)

Reaction velocity (μM s⁻¹)

1

5

100

50

Use these data to calculate an approximate value for KM. Is this valuelikely to be an overestimate or an underestimate of the true value? Explain.

Short Answer

Expert verified

The KM value of an enzyme with the substrate concentration and the reaction velocity is 9μM.

Step by step solution

01

Enzymes

Enzymes are biological protein catalyststhat change the rate of a process in a living organism. The molecule that binds to the enzyme's substrate binding site is referred to as the substrate.

02

KM_value of enzyme with substrate concentration and reaction velocity

v0=VmaxSKM+SKM+S=VmaxSv0KM=VmaxSv0-SKM=50μMs-11μM5μMs-1-1μM=50-55μM=9μM

Thus, theKM value of enzyme with the substrate concentration and the reaction velocity has been calculated.

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Most popular questions from this chapter

Explain why each of the following data sets from a Lineweaver Burk plot are not individually ideal for determining KM for an enzyme catalysed reaction that follows Michaelis-Menten kinetics.

Set A

1/[S] (mM⁻¹)

1/v0 (𝛍M⁻¹.s)

0.5

2.4

1.0

2.6

1.5

2.9

2.0

3.1

Set B

1/[S] (mM⁻¹)

1/v0(𝛍M⁻¹.s)

8

5.9

10

6.8

12

7.8

14

8.7

For an enzyme-catalyzed reaction, the presence of 5 nM of a reversible inhibitor yields a Vmax value that is 80% of the value in the absenceof the inhibitor. The KM value is unchanged. (a) What type of inhibition is likely occurring? (b) What proportion of the enzyme molecules have bound inhibitor? (c) Calculate the inhibition constant.

Ethanol in the body is oxidized to acetaldehyde (CH₃CHO) by liveralcohol dehydrogenase (LADH). Other alcohols are also oxidized byLADH. For example, methanol CH₃OH), which is mildly intoxicating, isoxidized by LADH to the quite toxic product formaldehyde (CH₂O). Thetoxic effects of ingesting methanol (a component of many commercialsolvents) can be reduced by administering ethanol. The ethanol acts as acompetitive inhibitor of the methanol by displacing it from LADH. Thisprovides sufficient time for the methanol to be harmlessly excreted bythe kidneys. If an individual has ingested 100 mL of methanol (a lethaldose), how much 100 proof whiskey (50% ethanol by volume) must beimbibe to reduce the activity of his LADH toward methanol to 5% of itsoriginal value? The adult human body contains -40 L of aqueous fluidsthroughout which ingested alcohols are rapidly and uniformly mixed.The densities of ethanol and methanol are both 0.79 g .cm-3. Assumethe KM values of LADH for ethanol and methanol to be 1.0 X 10⁻³Mand 1.0 X 10⁻²M, respectively, and that KI = KM for ethanol.

Identify the enzymes in Table 12-1 whose catalytic efficiencies are near the diffusion-controlled limit.

How does cytochrome P450 participate in drug metabolism?
See all solutions

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