Exam 8: Mechanisms and Inhibitors

The antibiotic penicillin is an example of a(n) ________________ inhibitor.

In conducting an experiment with a new drug, you find that regardless of the concentration of substrate, the drug is able to inhibit the enzyme activity. You are likely to not have a(n) ________________ type of inhibitor.

Where does cleavage of the scissile bond by chymotrypsin occur?

In this type of inhibition, the inhibitor can only bind to the ES complex to form an ESI complex.

The mechanism of chymotrypsin involves the formation of an unstable ________________-shaped intermediate that is stabilized by the oxyanion hole.

What conclusion can be drawn concerning an inhibitor if the KM is the same in the presence and absence of the inhibitor?

Why are substrate analogs used to monitor enzyme activity?

The straight-line kinetic plot of 1/V0 versus 1/S is called a ________________.

What is an affinity label?

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -____________: A type of catalysis where the proton donor is not water.

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -____________: A protease enzyme with a low pH optimum.

Which type(s) of inhibition can be reversed?

What is the difference between KM and KM app?

A protein that is optimally active at neutral pH is likely to have which in the active site?

What is the challenge for a protease to facilitate hydrolysis of a peptide bond?

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -____________: A molecule that is also known as a substrate analog.

Draw and describe the reaction pathway for a noncompetitive inhibitor.

A(n) ________________ inhibitor has a structure similar to the substrate and reversibly binds to the active site of the enzyme.

You measure the initial velocity of an enzyme in the absence and presence of two inhibitors. In each case, the inhibitor is at 10 µM. Shown in the table below is the primary data for all three cases. Construct a Lineweaver-Burk plot for each case. Calculate the KM and Vmax for each case, both graphically and mathematically. Determine the mechanism for each inhibitor and where each will interact on the enzyme. Initial Velocity (µmol/ml min) Enzyme Enzyme Enzyme [S] mM Alone + Inhibitor 1 + Inhibitor 2 0.33 1.65 1.05 0.79 0.50 2.13 1.43 1.02 1.00 2.99 2.22 1.43 2.00 3.72 3.08 1.79 5.00 4.00 3.80 2.00

A site-directed mutagenesis converting histidine-57 of chymotrypsin to a lysine results in an inactive enzyme even though lysine has an amino group in its side chain. Describe why the scientist may have thought this result surprising and why it wasn't.