Question

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Which of the following are characteristics of allosteric enzymes? Choose all that apply. Allosteric enzymes may have binding sites for regulatory molecules that are separate from active sites, conform to Michaelis-Menten kinetics. generally have more than one subunit. undergo conformational changes as a result of modulator binding, tend to have a hyperbolic curve of V0 vs. [S].

Answer 1

Concepts and reason

The enzymes, which change their conformation upon binding of an effector that affects the binding affinity at a different ligand binding site, are known as allosteric enzymes. The binding site of the effector is known as the allosteric site. They may have one or more allosteric sites.

Fundamentals

Enzymes are the biological catalysts that enhance the rate of biological reactions by lowering the activation energy required for the reaction to take place without being itself consumed in the reaction. Allosteric enzymes have allosteric sites where the effectors bind. The effectors that increase the activity of the protein are known as the allosteric activators and those that decrease the activity of a protein are known as the allosteric inhibitors. Allosteric enzymes can act either by feedback or feed forward mechanism.

The allosteric enzyme does not follow the Michaelis-Menten kinetics and have a sigmoidal kinetics instead of hyperbolic curve. They exhibit cooperativity that results in the saturation. The graph is drawn by taking reaction velocity (V_o) on Y-axis and Concentration of substrate [S] on X-axis.

The different characteristics of the allosteric enzymes are:

• They have different binding sites for the ligands apart from the active sites

• They have more than one subunit

• These enzymes have a sigmoidal curve and do not follow the Michaelis-Menten kinetics

• They undergo changes when a modulator binds to the active site. The modulator can be homotropic or heterotropic.

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