Cofactor

A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst (a substance that increases the rate of a chemical reaction). Cofactors can be considered "helper molecules" that assist in biochemical transformations.

Types of Cofactors

Cofactors can be divided into two main types:

• Coenzymes: Organic molecules that are often derived from vitamins and are required for enzyme function. Examples include NADH, FADH2, and Coenzyme A.
• Prosthetic groups: Tightly bound cofactors that are integral to the enzyme's structure. Examples include heme in hemoglobin and cytochromes.

Role in Enzyme Activity

Cofactors are essential for the proper functioning of many enzymes. They can:

• Stabilize enzyme structure
• Participate in the enzyme's catalytic mechanism
• Assist in the binding of the enzyme to its substrate

Examples of Cofactors

• Metal ions: Such as magnesium (Mg²⁺), zinc (Zn²⁺), and iron (Fe²⁺/Fe³⁺).
• Vitamins: Many vitamins act as precursors to coenzymes. For example, vitamin B1 (thiamine) is a precursor to thiamine pyrophosphate (TPP).

Cofactor vs. Coenzyme

While all coenzymes are cofactors, not all cofactors are coenzymes. Coenzymes are a subset of cofactors that are organic molecules, whereas cofactors can also include inorganic ions.

Related Concepts

• Apoenzyme: The protein part of an enzyme, without its cofactor.
• Holoenzyme: The complete, active enzyme with its cofactor.
• Metalloenzyme: Enzymes that contain one or more metal ions as cofactors.

See Also

• Enzyme
• Catalysis
• Metabolism
• Biochemistry
• Vitamin

Related Pages

• Enzyme
• Coenzyme
• Prosthetic group
• Metal ion
• Vitamin
• Apoenzyme
• Holoenzyme
• Metalloenzyme