Question

What does it mean for a molecule to show ALLOSTERIC properties? How does this relate to enzymes? That is, what does it mean if an enzyme is allosterically activated? How about inhibited? What mechanism(s) can explain how this is possible?

Answer 1

An allosteric molecule refers to the property of a molecule which does not exactly perform the primary function when bound to an enzyme. An enzyme has an active site to which a specific substrate binds and brings about conformational changes. These changes activate the enzyme to peform a catalysis reaction to generate a product. On the other hand, allosteric molecule is a molecule which does not bind to the active site, but binds to another site of the enzyme and modulates the rate of enzyme catalysis produced, either by increasing or decreasing it.

Most of the enzymes are allosterically inhibited but some type of catalysis can also activate them. This catalysis takes place independently of the active site and the kinetics are also different.

Similarly, binding of an allosteric molecule can also altogether prevent enzyme catalysis by permanently blocking or re-orienting the active sites so that the substrate cannot bind to it.

The mechanisms behind these modulations include formation of covalent, ionic or non-covalent bonds between the allosteric molecule and the enzyme.