Question

Which of the following is the most common method of regulation for a regulatory enzyme in a metabolic pathway?

Select one:

a. Phosphorylation

b. It is the first enzyme in the series

c. It is an allosteric enzyme

d. A product from the end of a pathway inhibits the enzyme, which operates higher up in the pathway.

Answer 1

a. Phosphorylation

Phosphorylation is the addition of phosphate groups to proteins, which is the most frequent regulatory modification mechanism in our cells. the addition of phosphoryl group to an enzyme is catalysed by kinase enzymes, while the elimination of this group is catalysed by phosphatase group. The frequency of phosphorylation as a regulatory mechanism is due to the ease of changing from phosphorylated form to dephosphorylated form.

Phosphorylation or dephosphorylation make the enzyme be functional at the time when the cells need the reaction to happen.The effects produced by addition of phosphoryl groups that regulates the kinetics of a reaction can be divided into two groups

• Phosphorylation changes the confirmation of an enzyme to a more active or inactive way.
• Phosphorylation modifies the affinity of an enzyme to the substrate.