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In 1876, Wilhelm Kuhne coined the term enzymes. Enzymes are proteins and they can act as catalysts. Louis Pasteur identified the substance from the living cell which enhances the rate of reaction, such a substance is known as a catalyst.
All enzymes are bio-catalysts that enhance the speed of reaction without itself undergoing any prior modification in the overall structure.
enzyme+substrate gives rise to product+enzyme.
Principles of enzymes
There are various principles of enzymes some of which are discussed below
Proximity and orientation effect- according to this principle, it is observed that the rate of reaction increases due to a certain effect caused by proximity and orientation.
Acceptors- It is the process through which acceptance and donation of protons happens.It should be noted that it is the situation where both acid and base can become the components of one reaction.
Bond strain- As per the principal of bond strain, the affinity of an enzyme causes structural reorganisation because it is more significant than substrate in the state of transition.
Metal ion catalysis- The theory of metal ion catalysis states that, due to presence of positive charges via coordination of charges, the process will only stabilise the negatively charged ions.
Covalent Catalysis- As per this principle, a covalent bond is often broken to further produce enzymes and does not cause any reduction in activation energy.
Electrostatic Catalysis- As per this principle, the process of stabilisation is done by creating electrostatic attraction between the two core components that is enzyme and substrate.
Properties Of Enzymes:
Enzymes are colloidal in nature and thermolabile in nature and they are very specific in their action with the substrate.
Classification Of Enzymes :
According to the international union biochemistry, system enzymes are broadly classified in 6 ways. they are
- Oxidoreductase
- A) Dehydrogenase
B)Oxidase
C)Oxygenase
- Transferase
- Hydrolase
- Lyase
- Isomerase
6.Ligase/Synthetase
Oxidoreductase:
It’s an enzyme that is involved in both biological oxidation and reduction reactions in the living cell.
Dehydrogenase:
It’s an enzyme that catalyses the removal of hydrogen atoms between the substrate or from one substrate to another substrate.
Oxidase: Oxidase is an enzyme that catalyses the removal of the hydrogen atom from one substrate to molecular oxygen, formation of water takes place.
Transferase:
It’s an enzyme that catalyses the transfer of groups from one substrate to another substrate.
Hydrolase:
hydrolase is an enzyme that brings about complete hydrolysis that is the addition of water molecules across the bond which leads to cleavage.
Lyase:
It’s an enzyme that catalyses the addition or removal of groups from molecules to form double bonds in a molecule.
Isomerase:
It’s an enzyme that brings about a complete isomerization reaction that is isomers having the same molecular formula but different compounds.
Ligase:
It’s an enzyme that brings about a complete synthesis reaction by joining together two molecules coupled with the breakdown of the pyrophosphate bond of atp/gtp.
Holoenzyme:
Holoenzyme – apoenzyme +cofactor
apoenzyme – a protein part of a complex molecule is called apoenzyme.
cofactor- non-protein of a complex molecule called the cofactor.
Coenzyme:
If the cofactor is loosely or weakly bound to the protein part of the apoenzyme, such a cofactor is designated as a coenzyme. all coenzymes are low molecular weight organic compounds, easily dialysable, and occur in a free state.
Isoenzymes:
Some enzymes may exist in two or more forms that have a similar catalytic activity or similar functions. isoenzymes are abundantly found in the serum, tissues of mammals, birds, insects, and amphibians. isoenzymes of ldh have immense value in the diagnosis of heart and liver and muscle diseases like acute hepatitis, myocardial infarction.
Enzyme inhibition:
The chemical substances which lead to decreasing the rate of enzyme-catalysed reactions are known as inhibitors, this phenomenon is known as inhibition.
The compound which inactivates the enzymes and thus adversely affects the rate of an enzyme catalysed reactions are known as inhibitors. This whole process is known as inhibition.
Classification of enzyme inhibition:
- Reversible Inhibition
- Competitive Inhibition
- Non-Competitive Inhibition
- Uncompetitive Inhibition
- Irreversible Inhibition
- Allosteric Inhibition
Reversible inhibition: Once inactivation is made by the inhibitor to the enzyme, thereafter this inhibitor is then disassociated from the enzyme due to non-covalent interactions or binding between the enzyme and the inhibitor. This is known as a reversible reaction.
Competitive inhibition: It is a reversible inhibitor, non-covalent binding between enzyme and inhibitor. The competitive inhibitor has a structural resemblance with the substrate, so it is regarded as a substrate analog. The site of attachment of both inhibitor and substrate is the same, the inhibitor competes with the substrate, therefore, binds to the active site of the enzyme.
Active site: Each enzyme possesses some specific site on its surface called an active site.
Non-competitive inhibition: It is reversible inhibition, non-covalent bonding between enzyme and inhibitor, non-competition between substrate and inhibitor with the enzyme.
Non-competitive inhibitors have no structural resemblance with substrates. The sites of attachment of both substrate and inhibitor are different. The inhibitor binds with the enzyme at a site other than the active site known as an allosteric site.
Allosteric enzymes: Some enzymes that possess specific sites other than active sites are called allosteric sites.
Types Of Allosteric Enzymes:
these are two types:
- positive allosteric
- negative allosteric enzymes.
Positive Allosteric Enzymes:
enzyme activity decreases when positive allosteric modulator binds to an allosteric site
Negative Allosteric Enzymes:
Enzyme activity decreases when the negative allosteric modulator binds to the allosteric site.
Enzyme structure:
As we know enzymes are proteins so a protein is made of amino acids which are linked together by a polypeptide chain in a linear chain. The specific order of amino acids in the protein is encoded by the dna sequence.
Generally, proteins have 4 structures… primary structure, the linear order of amino acids, secondary structure, the folding or coiling of amino acids due to hydrogen bonding.
Enzyme Inhibition And Repression:
Inhibition: some compounds or substances which induce the increased synthesis of enzymes are called inducers and this phenomenon is called induction.
Repression: Some proteins which repress the synthesis of enzymes are called repression.
Conclusion
In this article, you will learn about the nitty gritties of the functioning of enzymes. you get a fair insight about how an enzyme functions inside a body. Enzymes are bio-catalysts that enhance the speed of reaction without itself undergoing any prior modification.
