Coenzyme vs Cofactor: What’s the Difference?(review2024)

Enzymes are proteins that catalyze biochemical reactions in living cells. However, some enzymes require the assistance of non-protein molecules to function properly. These molecules are called cofactors and coenzymes. But what is the difference between them?

Cofactors

Cofactors are inorganic or organic molecules that bind to the enzyme and stabilize its structure or enhance its activity. Cofactors can be divided into two groups:

-Prosthetic groups: These are cofactors that bind tightly and permanently to the enzyme. They are usually metal ions or complex organic molecules, such as heme or flavin. For example, cytochrome c, an enzyme involved in the electron transport chain, contains a heme prosthetic group with iron.

-Co-substrates: These are cofactors that bind loosely and temporarily to the enzyme. They are usually small organic molecules that act as carriers of electrons or other groups between different enzymes. For example, NADH is a co-substrate that transfers electrons in oxidation-reduction reactions.

Coenzymes

Coenzymes are a specific type of co-substrates derived from vitamins. Vitamins are essential nutrients the body cannot synthesize and must be acquired from the diet. Coenzymes are involved in numerous metabolic pathways and regulate the activity of enzymes. Some examples of coenzymes are:

-Thiamine pyrophosphate (TPP): This coenzyme is derived from vitamin B1 (thiamine) and participates in the decarboxylation of alpha-keto acids, such as pyruvate. TPP is required for the function of pyruvate dehydrogenase, an enzyme that converts pyruvate to acetyl-CoA in the citric acid cycle.

-Pyridoxal phosphate (PLP): This coenzyme is derived from vitamin B6 (pyridoxine) and participates in the transamination of amino acids, such as alanine. PLP is required for the function of alanine aminotransferase, an enzyme that converts alanine to pyruvate in the gluconeogenesis pathway.

-Biotin: This coenzyme is derived from vitamin B7 (biotin) and participates in the carboxylation of substrates, such as acetyl-CoA. Biotin is required for the function of acetyl-CoA carboxylase, an enzyme that converts acetyl-CoA to malonyl-CoA in the fatty acid synthesis pathway.

NOTE: all coenzymes are cofactors, but not all cofactors are coenzymes. Remember, cofactors are the broader category, while coenzymes are a specific type of organic cofactor involved in carrying chemical groups.

What is the function of cofactors and coenzymes?

Cofactors and coenzymes are non-protein molecules that assist enzymes in catalyzing reactions. Cofactors are inorganic or organic molecules that stabilize the enzyme or the substrates, while coenzymes are small organic molecules that transfer electrons or other groups between molecules. Cofactors can be inorganic molecules such as magnesium ions, zinc ions, heme, and biotin. Coenzymes include NAD, FAD, and Coenzyme A.

Without cofactors or coenzymes, enzymes cannot effectively catalyze reactions. The enzyme may not function at all. When an enzyme acquires a coenzyme, it becomes a holoenzyme or active enzyme. Active enzymes transform substrates into the products necessary for an organism to perform essential chemical or physiological functions.

Summary

Cofactors and coenzymes are non-protein molecules that assist enzymes in catalyzing biochemical reactions. Cofactors can be prosthetic groups or co-substrates, depending on their binding affinity and the duration of their interaction with the enzyme. Coenzymes are a type of co-substrates derived from vitamins and act as carriers of electrons or other groups between enzymes. Cofactors and coenzymes are essential for properly functioning many metabolic pathways in the cell.