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Biochemistry

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Disruption of Feedback Inhibition

BIOCHM-M6TEYE

Enzymes are organized into metabolic pathways which are often regulated by feedback inhibition where the product of a pathway acts as a negative effector for an allosteric enzyme in the pathway. Typically, it is the first enzyme. This ensures that product won't be made when it has reached sufficient levels.

Effectors bind to the regulatory site on the enzyme and mutation to the gene that encodes the enzyme can alter the binding of those effectors. A hypothetical pathway regulated by feedback inhibition is shown.

$$A\xrightarrow [ 1 ]{ } B\xrightarrow [ 2 ]{ } C\xrightarrow [ 3 ]{ } D\xrightarrow [ 4 ]{ } E$$

Assume this pathway shows feedback inhibition.

Which choice best describes what would happen to the level of E if a mutation caused the regulatory site for enzyme 1 to have a ${ S }_{ 0.5 }$ value of 0.1 nM for E and the value for the unmutated enzyme is 1 nM?

A

The level of E would increase.

B

The level of E would decrease.

C

The level of E would not change.

D

There is not enough information to determine this.