Exam 6: Mechanisms of Enzymes

The reaction catalyzed by a certain phosphatase enzyme is found to follow ping-pong kinetics and involves the transfer of a phosphate group from substrate A to substrate B. Which mode of catalysis is likely for this reaction?

Active trypsin formation by the action of enteropeptidase can be viewed as the master activation step because

Zymogens are inactive enzyme precursors which are made active by

A histidine was determined to be the critical residue involved in an enzyme-catalyzed reaction. If the pK_a of the histidine is known to be 6.5 in the active site and the pH of maximum catalytic activity is 7.2, what is likely the primary role of histidine in the catalytic reaction?

A key role of the hydroxyl group at position 6 in the purine ring in the formation of a transition state by the enzyme adenosine deaminase is obtained by comparing a and a .

Antibodies raised against transition state analogs are always enzymatic.

An enzymeʹs active site contains an arginine residue and a glutamate residue with pK_aʹs of 2.9 and 9.1, respectively. Both residues are actively involved in the catalytic mechanism and they are the only two ionizable residues in the active site. What would you expect for the optimum pH of the enzyme?

The movement of is key to understanding chemical and enzymatic reactions.

On the energy diagram below, which point represents an intermediate?

Which amino acid is least likely to participate in acid-base catalysis?

Glycoside hydrolases such as bacterial cellulase have been shown to differ in mechanisms from that of lysozyme. They

Acid-base catalysis is estimated to accelerate a typical enzymatic reaction by what factor?

Superoxide dismutase enzyme catalysis is faster than the rate of diffusion because it

The active site of a certain enzyme contains a serine residue. When the enzyme is incubated for a short time with its substrate, a form of the enzyme in which the active site serine is acetylated can be isolated and purified. In the native protein the serine is never found to be acetylated. This information supports .

When the concentration of a substrate inside a cell falls below the substrate concentration at half maximal velocity .

Which modes) of catalysis is/are classified as chemical effects? 1. Transition state stabilization 2. Acid-base catalysis 3. Covalent catalysis 4. Proximity effect

In this reaction, the carbon is .

Zymogens are often active only in the environment in which they are functional.

Which statement does not apply to transition states?

Intermediates are more stable and have longer lifetimes than transition states.