Allosteric Regulation

Question 1

What does a low Km indicate?

Answer 1

R state (more active) -> low Km (uninhibited state). Activators favour the R state

Question 2

What does a high Km indicate?

Answer 2

T state (less active) -> high Km (inhibited state). Inhibitors favour the T state

Question 3

What is Km?

Answer 3

Michaelis-Menten constant

Km=1/2Vmax (same Vmax for R and T states)

Question 4

What is an allosteric regulator of PFK-1?

Answer 4

ATP and citrate are negative modulators - high ATP lowers the activity while low ATP doesn’t

F-2,6bisP and AMP, ADP are positive modulators - The presence of F-2,6bisP increases the activity

Question 5

What is an allosteric regulator in liver and muscle (hexokinase)?

Answer 5

Liver- Glucokinase
Low Km value
Stabilisation of the R state

Muscle - Hexokinase
High Km value
Stabilisation of the T state
G-6-P is allosterically inhibited by the product of the reaction it catalyses

Question 6

Pyruvate kinase allosteric regulators

Answer 6

Liver: L-PK (inhibited by ATP and alanine - activated by F-1,6-bisP)

Muscle: M-PK (inhibited by ATP and alanine- activated by F-1,6-bisP)