Question

Which of the following coenzymes is a derivative of pantothenic acid (vitamin B complex)?
(a)NAD
(b)NADP
(c)FAD
(d)CoA

Answer 1

A coenzyme is a type of cofactor. Cofactors are non-protein constituents that bind to the enzyme to make the enzyme catalytically active. In such cases, the protein part is known as apoenzyme which binds with the cofactor to form the holoenzyme which is the whole active enzyme.

Complete answer:
Pantothenic acid which is also known as vitamin ${ B }_{ 5 }$ is a water-soluble essential nutrient that is present naturally in some foods or can be taken as a dietary supplement. The main function of pantothenic acid is the synthesis of coenzyme A or CoA and acyl carrier protein. About 85% of dietary pantothenic acid is converted into CoA and this conversion takes place by the enzyme pyruvate dehydrogenase. Coenzyme A is a primary substrate for the Krebs cycle, essential for the fatty acid synthesis and degradation and transfer of acetyl and acyl groups.

Additional Information: Let us learn more about the cofactors of enzymes. Cofactors are classified into three types known as:
Prosthetic groups: Prosthetic groups are made up of organic compounds and can be differentiated from other cofactors by the fact that these groups are in very close association with the apoenzyme by binding to it tightly. Example- The enzymes catalase and oxidase which break down hydrogen peroxide into water and oxygen, heme is the prosthetic group of these enzymes.
Coenzymes: Coenzymes are also organic compounds but their association with the apoenzyme takes place only during the course of catalysis. Vitamins make up many coenzymes for example the coenzyme nicotinamide adenine dinucleotide (NAD) contains vitamin niacin.
Metal ions: Metal ions form coordination bonds with the side chains of the active site of the enzyme as well as the substrate thus help in the catalysis of the reaction. An example includes Zn as a cofactor for the enzyme carboxypeptidase.
So, the correct option is ‘CoA’.

Note:
-Coenzymes can act as cofactors for a number of different enzyme-catalyzed reactions.
-The importance of cofactors is realized by the fact that the catalytic activity stops after the cofactor is removed from the enzyme.
-The enzyme carboxypeptidase is a proteolytic enzyme that is synthesized in the pancreas and secreted into the small intestine.