Question

What are characteristics of allosteric enzymes?

(A) They tend to have a hyperbolic curve of V0 vs. [S].
(B) They may have binding sites for regulatory molecules that are separate from active sites.
(C) They generally have more than one subunit.
(D) They conform to Michaelis–Menten kinetics.
(E) They interconvert between a more active form and a less active form.

Answer 1

Allosteric enzymes have both a binding site, for substrate binding and catalysis, and an allosteric site, for regulation of enzyme activity. They generally have more than one subunit and can interconvert between a more active form and a less active form. Allosteric enzymes show a hyperbolic curve in the graph plotting the rate of reaction against the concentration of the substrate.

Step-by-step explanation:

Allosteric enzymes have both a binding site, for substrate binding and catalysis, and an allosteric site, for regulation of enzyme activity. When a regulator molecule binds to the allosteric site of an enzyme, a conformational change occurs in the enzyme active site, affecting substrate binding and reaction rates. Allosteric regulation can be either positive, increasing reaction rates, or negative, decreasing reaction rates.

Allosteric enzymes generally have more than one subunit, allowing for highly-controlled reaction rates. They can also interconvert between a more active form and a less active form. The action of allosteric enzymes can be depicted using a hyperbolic curve in the graph plotting the rate of reaction (V0) against the concentration of the substrate ([S]).

Answer 2

(B) They may have binding sites for regulatory molecules that are separate from active sites.

(C) They generally have more than one subunit.

(E) They interconvert between a more active form and a less active form.

Step-by-step explanation:

Allosteric enzymes are the regulatory enzymes that have a specific site for binding of modulator or effector molecule. The activity of these enzymes is altered by the noncovalent binding of modulators at the allosteric site. The binding of the modulator brings about a conformational change in the allosteric enzymes.

The relatively inactive conformation of these enzymes is called T state while the active conformation is the R state. Most of the allosteric enzymes have multiple subunits and deviate from Michaelis–Menten kinetics and exhibit a sigmoid saturation curve of V0 vs. [S].