Question

Non-competitive inhibitor changes active site of an enzyme after binding at?

Answer 1

Enzymes can be defined as biological polymers that can catalyse biochemical reactions. They are proteins having catalytic capabilities crucial to perform different processes. Enzymes carry out metabolic processes and other chemical reactions which are necessary to sustain life.

Complete answer:
In non-competitive inhibition, there is no structural similarity between inhibitor and substrate. The substrate binds with the enzyme at different sites other than the active site. Non-competitive inhibitor changes the active site of the enzyme after binding at an allosteric site.

Therefore, there is no competition between substrate and inhibitor as the formation of enzyme inhibitor, enzyme-substrate and enzyme-substrate inhibitor take place. The inhibitor and substrate can bind simultaneously to the same enzyme molecule as their binding sites are different and hence do not overlap. The maximum velocity is lowered in non-competitive inhibition by reducing the proportion of enzyme molecules that are bound to the substrate.

So, the non-competitive inhibition cannot be overcome by increasing substrate concentration because even though the substrate is still binding the enzyme-substrate inhibitor does not form a product and hence maximum velocity and concentration of active enzyme is reduced by the inhibitor.

Note:
i) Substances that decrease the rate of an enzyme-catalysed reaction are called enzyme inhibitors and the process is known as enzyme inhibition. Enzyme inhibition is differentiated into
- Reversible inhibition
- Irreversible inhibition.
ii) In reversible inhibition, there is the dissociation of inhibitors from the enzyme-inhibitor complex. There are three types of reversible inhibitions:
- Competitive inhibition
- Non-competitive inhibition
- Uncompetitive inhibition.
iii) Allosteric enzymes consist of more than one protein subunit and they have more than one active site.