Profile
Settings
Refer your friends
Sign out
Cofactor
Cofactor refers to the little, non-protein, helper, or accessory molecule essential to convert an inactive apoenzyme to an active condition called holoenzyme or complete enzyme. Apoenzymes are conjugated proteins, which need an extra factor to act like a helpful or catalytically active enzyme.
An enzyme includes an active site where the particular substrate combines tightly. Oppositely, the allosteric site is the area where the allosteric activators and inhibitors can unite predominantly to accelerate or restrain the enzymatic activity. Cofactors can be inorganic (comprises metal ions) and organic (comprises coenzymes and prosthetic groups).
The cofactors are categorised into two kinds as per the chemical nature and connection with an enzyme.
- A big group of metal ions like (Mg 2+, Cu +, Mn 2+) are inorganic cofactors that act as necessary trace elements in our diet. Enzymes that trigger in association with metal ions are referred to as metal activated enzymes or metalloenzymes.
- In a few cases, an enzyme must be allosterically controlled by binding definite inorganic elements. Here, the inorganic elements are usually effector molecules but not considered cofactors. For example, calcium partakes in the allosteric management of nitric oxide synthase, adenylate kinase, etc.
- Organic cofactors comprise coenzymes and prosthetic groups, which we will confer below in the definition of coenzyme.
Cofactor Instances
Below are a few examples of the enzymes and their cofactors:
- Fe2+ or Fe3+: Catalase, Peroxidase, etc.
- Cu2+: Cytochrome oxidase, superoxide dismutase
- Zn2+: Alcohol dehydrogenase, Carboxypeptidase
Coenzyme
Coenzyme denotes the co-substrate or secondary substrate that composes a group of stationary, non-protein, and small organic molecules of little molecular weight (< 1000Da). They straight take part in the enzyme catalytic reactions.
The coenzyme is a sub kind of cofactor molecule, which are organic and help in attaching a substrate molecule to an enzyme’s active site. Coenzymes bind faintly to the inactive protein or apoenzyme, which can be effortlessly separated by dialysis. It plays an irrefutable role in an immobile enzyme to function.
As we have seen above, some enzymes require a particular carrier or molecules to catalyse a reaction. Therefore, the coenzyme acts as a co-substrate that mainly connects with the substrate molecules, endures a few alterations during enzyme movement, and afterwards redevelops or functions as a recyclable shuttle.
Prosthetic groups are mixed organic groups that combine covalently with the protein. Their division from an enzyme is complex or only part of the enzyme denaturation. For example, heme is a prosthetic group holding an iron atom in the haemoglobin molecule.
Coenzyme Instances
Below are a few examples of coenzymes of vitamin B-complex:
- Thiamine (B1 vitamin)
Thiamine pyrophosphate is the coenzyme of thiamine precursor of vitamin B1 that partakes in the decarboxylation, aldehyde group transport, etc.
- Riboflavin (B2 vitamin)
FAD and FMN is the flavin molecule that works as a coenzyme of vitamin B2, which dynamically contributes to the redox reactions.
The disparity between cofactor and coenzyme is mostly distinguished based on chemical nature and purpose. Cofactors comprise a huge group of helper molecules (inorganic or organic). On the other hand, cofactors are minute organic molecules.
Coenzymes considerably work as carrier materials to alter the immobile protein (the apoenzyme) into the lively form (holoenzyme). On the contrary, cofactors act as biocatalysts that just fasten the enzymatic reaction within a cell.
Parameter | Cofactors | Coenzymes |
|---|---|---|
Alternative names | Some alternative names for Cofactor are helper molecules or accessory molecules | Some alternative names for Coenzyme are co-substrate or secondary substrate |
Definition | Cofactors are the nonprotein helper molecules needed for the action of apoenzymes or enzymes prepared of conjugated proteins, which may contain simple metal ions or complex organic groups | Coenzymes are the inactive non-protein organic co-substrates (with no protein part or apoenzyme) that straight partake in the enzyme catalysis |
Chemical nature | Cofactors could be organic and inorganic molecules | Cofactors are the organic molecules |
Association with an enzyme | Cofactors can covalently or noncovalently connect with an apoenzyme | Cofactors attach limply or non-covalently with an apoenzyme |
Separation | Division of cofactors can be simple or hard (separates only after enzyme denaturation) | Coenzymes are connected quickly to an apoenzyme and can be effortlessly detachable |
Dialysability | Some cofactors are dialysable, whereas others are non-dialysable | Coenzymes are dialysable |
Classification | Cofactors are classified into two kinds based on the enzymatic activity, specifically inorganic and organic cofactors | Coenzymes are a sub kind of cofactor that comes under the group of organic cofactors |
Function | Cofactors act as the helper molecule that quickens the enzymatic reaction | Coenzymes act as the substrate shuttle that aids in the translocation of atoms or groups |
Integral part | A cofactor is a combined term that symbolises activator metal ions, coenzymes, and prosthetic groups essential for an inactive enzyme to function | The essential part of the coenzymes are vitamins |
Conclusion
Thus, we can conclude that the cofactor is a collective term that comprises inorganic metal ions, organic compounds (coenzymes), and organic prosthetic groups. Coenzymes and cofactors are the supplementary factors that aid enzyme catalysis by combining with the inactive protein that alone cannot alter substrate into product.
