The following statements refer to Phosphoenolpyruvate carboxykinase (PEPCK). Which statement in A through D is INCORRECT?
a. ADP is a negative allosteric modifier
b. its activity is increased following phosphorylation
c. it catalyzes the synthesis of a high energy bond
d. it is one of the energy consuming steps in gluconeogenesis
e. it catalyzes a decarboxylation reaction
Ans: b ). Option b is the incorrect statement regarding the PEPCK enzyme.
Dephosphorylation increases the activity of PEPCK.
When the energy status of the cell is high then gluconeogenesis takes place and there will be a lot of ATP available. This promotes gluconeogenesis. If energy status is low, that is free ADP is available in large amounts, then gluconeogenesis will not take place. The free ADP allosterically inhibit PEPCK.
PEPCK catalyzes the conversion of oxaloacetate to phosphoenolpyruvate by decarboxylation. In this step 1 GTP molecule is used to create a high energy bond.
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