Types of Cofactors

Cofactors can be broadly classified into two main types:

Inorganic Cofactors (Metal Ions)

• These include metal ions such as iron (Fe²⁺/Fe³⁺), magnesium (Mg²⁺), zinc (Zn²⁺), copper (Cu²⁺), and manganese (Mn²⁺). They are essential for stabilizing enzyme structure and participating directly in enzymatic reactions.

Organic Cofactors (Coenzymes)

These are organic molecules that often derive from vitamins and assist enzymes in their catalytic activity. Examples include:

• NAD⁺ (Nicotinamide adenine dinucleotide): Involved in redox reactions.
• FAD (Flavin adenine dinucleotide): Participates in redox reactions.
• Coenzyme A: Important for fatty acid metabolism and the Krebs cycle.
• Vitamins: Such as Vitamin B6 (pyridoxine) and Vitamin B12 (cobalamin), which act as coenzymes in various metabolic processes.

Additionally, cofactors can be classified based on how tightly they are bound to the enzyme:

• Prosthetic Groups: These are tightly or covalently bound to the enzyme and remain attached during the enzyme’s catalytic cycle (e.g., heme in hemoglobin).
• Cosubstrates: These are loosely bound and may be released from the enzyme during the reaction. They often participate in the reaction as substrates themselves (e.g., ATP).

Cofactors are non-protein chemical compounds or metallic ions that are essential for an enzyme’s biological activity. They can be organic molecules, called coenzymes, or inorganic ions. The cofactor’s function is to assist enzymes in catalyzing reactions by stabilizing transition states, enhancing substrate binding, or participating directly in the chemical reaction. Common cofactor examples include vitamins and metal ions like magnesium and iron.