Question

An allosteric inhibitor of the enzyme acts by binding to the
A. Substrate
B. Product
C. Catalytic site of enzyme
D. Noncatalytic site of enzyme

Answer 1

Hint:-For most, if not all, of the processes needed for life, enzymes are required. By reducing the activation energy required for the reaction to occur, enzymes catalyse a reaction. However, to ensure that the levels of the substance do not rise to undesired levels, enzymes need to be closely regulated. Enzyme inhibition accomplishes this.

Complete answer:
By binding to the allosteric site, an allosteric inhibitor affects the protein conformation at the enzyme's active site, which ultimately affects the structure of the active site. The enzyme is now no longer able to bind to its unique substrate. The enzyme will now not carry out its catalytic function , i.e. the enzyme is now inactive. This process is called allosteric inhibition.

In comparison to the hyperbolic curve shown by Michaelis-Menten Enzymes, allosteric enzymes show a sigmoidal curve. This is since, as the substrate binds to the enzyme, most allosteric enzymes contain several subunits that may influence each other $K_{0.5}$, which is the substrate concentration for half-saturation, $V_{max}$ or both, may be influenced by inhibition. This results in a curve shift to the right and moves the curve down in the case of a $V_{max}$ reduction.

Allosteric enzymes have two states: the "T" state is dubbed a low affinity state and the "R" state with high affinity. Inhibitors function by binding to the T state of an allosteric enzyme preferentially, allowing this low affinity state to be retained by the enzyme. This is incredibly beneficial in limiting the quantity of the output of an enzyme, so the output will then proceed to suppress the same type of enzyme to ensure that the quantity of the product is not unnecessary. This is known as the inhibition of feedback.

For instance , in order to avoid increased formation of pyruvate, ATP allosterically inhibits pyruvate kinase, so less ATP is gradually produced. In addition, citrate, an intermediate in the Kreb cycle, is allosterically inhibited by phosphofructokinase. This means that when there is elevated ATP generation from the Kreb 's cycle, glycolysis will be limited.

From these discussions we can conclude that the allosteric inhibitor of the enzyme acts by binding to the noncatalytic site of the enzyme.

Therefore the correct answer is option (D).

Note:- Needs and situations differ from cell to cell and, over time, shift in individual cells. Stomach cells , for example, require different enzymes than cells for fat storage, skin cells , blood cells, or nerve cells. Often, during the time that accompanies a meal, a digestive cell works even harder to absorb and break down nutrients compared to several hours following a meal. When these cellular demands and requirements change, the concentrations and functionality of various enzymes change as well. They tend to be closely regulated since enzymes direct and regulate a cell 's metabolism.