Enzyme Inhibition And Its Types

        ENZYME INHIBITION:

Today our topic is enzyme inhibition which is define as
                                        The phenomene in which enzyme fail to catalyze a reaction is called enzyme inhibition
First question that arise in our mind is that why enzyme fail to catalyze a reaction? Answer is enzyme fails to catalyze a reaction due to ENZYME INHIBITOR
What is enzyme inhibitor?
It is a substance that attach to enzyme but not change into product
Why enzyme inhibitor not change into product?
Enzyme inhibitor may be similar to substrate or not. Take first condition in which enzyme inhibitor similar to substate so it attach to active site of enzyme. But it is not 100% similar due to which enzyme doesnot change into product and in result enzyme active site don't available for substrate because it is attach to enzyme inhibitor. Second condition is that when enzyme inhibitor is not similar to substrate. If it is not similar to substrate then how it attach to active site? Actually this type of enzyme inhibitor doesnot attach to active site. It attach to enzyme other then binding site which is known as ALLOSTERIC SITE. As a result enzymes activity stops
TYPES OF ENZYME INHIBITION:
1-Competitive inhibition
2-Non-competitive inhibition

COMPETITIVE INHIBITION:

A type of enzyme inhibition in which enzyme activity is blocked by the presence of chemical which is competing with substrate to get bind with active site. As we discussed that enzyme inhibitor is similar to substrate in that case both substrate and inhibitor trying to attach to active site mean their goal was same because both have ability to get bind with active site. The level of inhibition is depend on the releative concentration of substrate and inhibitor, If the concentration of substrate is increased releative to the concentration of the inhibitor, the active site will usually  be occupied by the substratee. Usually competitive inhibition is temporary, and the inhibitor evantually leaves the enzyme hence it is also called REVERSIBLE INHIBITION. An example of competitive inhibitor is MALONATE

NON-COMPETITIVE INHIBITION:

In non-competitive inhibition inhibitor molecule binds to an enzyme other then active site. The other binding site of enzyme is called ALLOSTERIC SITE. The non-competitive inhibitor is of two type
1-Reversible non-competitive inhibitor
2-Irreversible non-competitive inhibitor:
Reversible non-competitive enzyme inhibitor  block the enzyme active temporaly. They don't work by preventing the formation of enzyme-substrate complex, but work by preventing enzyme-product complex. Feedback inhibition is a type of this inhibition
Irreversible non-competitive enzyme inhibitor block the enzyme activity by changing its shape so in this way substrate cannot bind to the active site. Example of such inhinitor are cyanides and salts of heavy metal. Cyanides are potent poison for living organism because they can block the enzyme cytochrome oxidase essential for cellular respiration. They block this activity by combining with iron present in prosthetic group. Ions of heavy metal can block the enzyme activity by combining with tiol group(-SH) in the enzyme breaking the disulphide bridge. These bridges are important for keeping tertiary structure of enzyme. When these bridges are broken enzyme become denaturered and inactive.

FEEDBACK INHIBITION:

When activity of enzyme is inhibited by its own product. It is called feedback inhibition
Example:
Amino acid asparate become amino acid threonine by a sequence of five enzymetic reaction. When threonine(last product) is present in large amount. Its bind to allostratic site of enzyme1 on this pathway. In this conversion of asparate into threonine stops. As threonine use by celllular events its amount decreases and finally it would completely consumed then threonine leave active site of enzyme 1 on this pathway and threonine production again started