Coenzyme vs Cofactor
Enzymes are essential biological macromolecules. Enzymes are the biological catalysts, which increases the rate of biological reactions under very mild conditions. Enzymes are proteins, so when they are subjected to high level of heat, salt concentrations, mechanical forces, organic solvents and concentrated acid or base solutions, they tend to denaturize. The two properties that apparently make an enzyme a powerful catalyst are:
- Their specificity of substrate binding
- Optimal arrangement of catalytic groups in an active site of the enzyme
Normally enzymes need very specific conditions to function. For example, they function at optimal temperatures, pH conditions, etc. Other than these, enzymes need the support of another molecule or an ion to have the specific function.
What is Cofactor?
Cofactors are the assisting chemical species (a molecule or an ion), which are bound to enzymes in order to bring out the enzyme’s biological activity. Most of the enzymes need cofactors to exert their activity, whereas some enzymes may not need them. An enzyme without the cofactor is called an apoenzyme. When an apoenzyme is together with its cofactor, it is known as a holoenzyme. Some enzymes may associate with one cofactor while some may associate with several cofactors. Without the cofactors, the enzyme activity will be lost. Cofactors can be broadly divided into two as organic cofactors and inorganic co factors. Inorganic cofactors mainly include metal ions. These metal ions are often needed in trace amounts. Magnesium is essential for hexokinase, DNA polymerase and Glucose-6-phosphate enzymes. Zinc is an essential metal ion for alcohol dehydrogenase, carbonic anhydrase and DNA polymerase function. Other than magnesium and zinc, there are other metal ions like cupric, ferrous, ferric, manganese, nickel etc, which are associated with different types of enzymes. Metal ions in enzymes can participate in the catalytic process in three major ways.
• By binding to the substrate as to orient it properly for reaction
• By electrostatically stabilizing or shielding negative charges
• By facilitating oxidation, reduction reaction through reversible changes in the metal ions’ oxidation state
Organic cofactors are mainly vitamins and other non-vitamin organic molecules like ATP, glutathione, heme, CTP, coenzyme B, etc. Organic cofactors can be further divided into two as coenzyme and prosthetic group. Prosthetic groups have been bound tightly with the enzyme and participate in the enzyme catalysis reaction. During the reaction, the enzyme- prosthetic group complex may undergo structural changes, but they are coming to the original state when the reaction is over. FAD is a prosthetic group of succinate dehydrogenase enzyme, which reduces to FADH2 in the process of converting succinate to fumarate.
What is Coenzyme?
Coenzymes are smaller organic molecules than the enzyme (which is a protein). Coenzymes are mainly organic molecules, and many are derived from vitamins. For example, niacin produces the coenzyme NAD+ that is responsible for oxidation reactions. Further, coenzyme A is made from pantothenic acid, and they participate in reactions as acetyl group carriers.
What is the difference between Coenzyme and Cofactor?
• Coenzymes are a type of cofactors.
• Coenzymes are organic molecules, whereas there can be inorganic cofactors also.
• Coenzymes are bound loosely with the enzyme, and there are some other cofactors, which are bound tightly to the enzyme.