Fad – Flavin Adenine Dinucleotide

flavin adenine dinucleotide (FAD) is a redox cofactor, more specifically a prosthetic group, involved in several important reactions in metabolism.

1. FAD – Flavin Adenine Dinucleotide

2. FAD It derived from riboflavin, vitamin B2 They have function in oxidation and reduction reactions FAD is act as coenzyme for various enzymes like α- ketoglutarate dehydrogenase, succinate dehydrogenase, xanthine dehydrogenase, acyl co dehydrogenase . It exist in three different redox states, which are, Quinone (FAD) - fully oxidized form Semiquinone (FADH ) -half reduced form Hydroquinone (FADH2) - fully reduced form

3. STRUCTURE OF FAD Flavin adenine dinucleotide consists of two main portions an adenine nucleotide (adenosine monophosphate) a flavin mononucleotide It is bridged together through their phosphate groups . Riboflavin is formed by a carbon-nitrogen (C-N) bond between a isoalloxazine and a ribitol .

4. STRUCTURE OF FAD

5. FAD can be reduced to FADH2 through by the addition of two H+ and two e-.

6. Basic Physical and Chemical Properties Based on the oxidation state, flavins take specific colors when in aqueous solution. FAD (fully oxidized) is yellow, FADH(half reduced) is either blue or red based on the pH, FADH2the fully reduced form is colorless

7. FAD Chemical States

8. Biosynthesis of FAD FAD plays a major role as an enzyme cofactor originating from riboflavin. Bacteria, fungi and plants can produce riboflavin, but other eukaryotes, such as humans, have lost the ability to make it. humans must obtain riboflavin, also known as vitamin B2, from dietary sources. Riboflavin is generally absorbed in the small intestine and then transported to cells via carrier proteins.

9. FAD is synthesized in the cytosol and mitochondria and potentially transported where needed. Step 1 Riboflavin kinase (EC 2.7.1.26) adds a phosphate group to riboflavin to produce flavin mononucleotide. Step 2 FAD synthetase attaches an adenine nucleotide; both steps require ATP .

10. Biosynthesis

11. Biological Functions and Importance catalyze difficult redox reactions such as dehydrogenation of a C-C bond to an alkene FAD has a more positive reduction potential than NAD+ and is a very strong oxidizing agent. FAD plays a major role as an enzyme cofactor FAD-dependent proteins function in a large variety of metabolic pathways, electron transport, role in production of ATP The reduced coenzyme FADH2 contributes to oxidative phosphorylation in the mitochondria. FADH2 is reoxidized to FAD, which makes it possible to produce 1.5 equivalents of ATP.

12. DNA repair nucleotide biosynthesis FAD-dependent enzymes that regulate metabolism are glycerol-3-phosphate dehydrogenase (triglyceride synthesis) and xanthine oxidase involved in purine nucleotide catabolism beta-oxidation of fatty acids redox flavoproteins that non-covalently bind to FAD like Acetyl-CoA-dehydrogenases which are involved in beta-oxidation of fatty acids amino acid catabolism catabolism of amino acids like leucine ( isovaleryl -CoA dehydrogenase), isoleucine, (short/branched-chain acyl-CoA dehydrogenase), valine ( isobutyryl -CoA dehydrogenase), and lysine synthesis of other cofactors such as CoA, CoQ and heme groups.

13. EXAMPLES OF FAD DEPENDENT ENZYEMS

14. THANK YOU