The graph of enzyme activity versus substrate concentration for an enzyme has a sigmoidal (S-shaped) appearance.Such an activity curve indicates which type of enzyme?

Question

Quizplus · Accepted Answer

A sigmoidal activity curve is characteristic of a multisubunit allosteric enzyme. In multisubunit enzymes, subunits can have different conformations, and binding of substrate or other effectors can induce conformational changes that affect the activity of the enzyme as a whole. This type of regulation enables the enzyme to respond to changes in the environment and maintain a steady-state of product formation. Noncompetitive and competitive inhibition, nonallosteric regulation, and irreversible phosphorylation are not associated with sigmoidal activity curves.

The Graph of Enzyme Activity Versus Substrate Concentration for an Enzyme