No, FAD (flavin adenine dinucleotide) is not a protein. It is a coenzyme.
What is FAD?
FAD is a crucial redox-active coenzyme involved in a wide array of enzymatic reactions within metabolism. It is typically associated with various proteins, acting as a helper molecule to facilitate their function.
FAD vs. Flavoproteins
While FAD itself is not a protein, it often works in conjunction with proteins. A protein that contains either FAD or flavin mononucleotide (FMN) is called a flavoprotein. The flavoprotein is the protein, and the FAD (or FMN) is the flavin group bound to it. This flavin group is essential for the protein's enzymatic activity.
Key Differences Summarized
| Feature | FAD | Flavoprotein |
|---|---|---|
| Definition | Redox-active coenzyme | Protein containing FAD or FMN |
| Function | Facilitates enzyme reactions | Catalyzes specific reactions |
| Composition | Adenine, ribose, phosphate, flavin | Amino acids + FAD/FMN |
| Example | Part of succinate dehydrogenase | Succinate dehydrogenase itself |
In essence, FAD is a component that assists certain proteins (flavoproteins) in carrying out their enzymatic duties. It is akin to a tool that a carpenter (the protein) uses to build something; the tool is not the carpenter itself.
