Induced Fit Mechanisms

Question 1

What is an induced fit mechanism?

Answer 1

Conformational change upon substrate binding (using enzyme-substrate binding energy) forms the active site, and activates catalysis.

Question 2

What reaction does hexokinase catalyse?

Answer 2

Glc => Glc-6-P in glycolysis

Question 3

How is unwanted ATP hydrolysis prevented in hexokinase?

Answer 3

The conformational change excludes water.

Question 4

What are the possible mechanisms for hexokinase?

Answer 4

a) Nucleophilic attack of the C6-OH in glc on the phosphate- gives electrons to oxygen to break the P-O-P bond in ATP
b) Addition mechanism involving an intermediate. ADP forms to stabilise the intermediate

Question 5

What type of catalysis is hexokinase an example of?

Answer 5

Metal-ion catalysis as the magnesium ions stabilise the negatively charged groups.

Question 6

Where is maltose binding protein found and what does it do?

Answer 6

In the periplasm of E.coli. Binds any maltose found in the periplasm and transfers it to a translocator, which passes it over the inner membrane.

Question 7

What is the binding energy of maltose used for?

Answer 7

To form a closed structure.

Question 8

How can maltose binding protein be used to produce a biosensor?

Answer 8

By coupling a fluorophore to a lys residue in MBP. A different fluorescence is emitted whether the MBP is in the closed or open structure.