1^st part:

Enzyme inhibitors-

An enzyme inhibitor is a molecule of a bunch of molecules that bind to an enzyme and somehow inhibits or decreases its activity.

Many drugs are enzyme inhibitors because they can block the active sites of the enzymes or changes shape of it and causes prevention in the interaction between the enzyme and its substrate or inhibiting its catalytic activities.

2^nd part:

Enzyme inhibitors can be classified into 2 separate categories according to their mode of attachment on the active site of the enzymes-

(i)Competitive inhibitors & (ii) non-competitive inhibitors .

3^rd part:

Inhibition of enzymatic activity by enzyme inhibitors-

(i)Competitive inhibitors-

• This kinds of inhibitors (drugs) usually mimic the chemical structures of a natural substrate which is to bind in the active site of the enzyme.

• They compete with the natural substrate for their attachment on the active sites of enzyme and thus inhibiting the catalytic activity of that enzyme.

(iii) Non-competitive inhibitors –

• These drugs do not bind to the exact active site of the enzyme.

• Instead, it binds to another site of the enzyme than the active site, which is generally called allosteric site.

• This binding of the inhibitors at allosteric site brings change in the shape of the active site of the enzyme in such a manner that it will not be possible for the substrate to recognise and bind to the active site of the enzyme.

• Therefore non-competitive inhibitors destroy enzymatic action without any direct interaction with the active site of the enzyme.

• If the bond formed between the enzyme and the inhibitor during drug-target interaction is strongly covalent by nature then the enzyme gets blocked permanently that as that bond cannot be degraded easily; then the body has to degrade the whole enzyme-inhibitor complex and synthesize new enzyme, instead.