Biochemistry free online lectures for medical students by Biochemistry Club
Niacin (Vitamin B3)
- Niacin or Nicotinic acid is also known as the Pellagra Preventing Factor of Goldberger.
- Niacinamide is the active form of the Vitamin B3 that is present in the tissues.
- It was originally named as Coenzyme I but finally as NAD+.
- The biologically active forms of niacin are Nicotinamide Adenine Dinucleotide (NAD+) and its phosphorylated derivative, Nicotinamide Adenine Dinucleotide Phosphate (NADP+).
- The Niacin is attached to ribose phosphate to a mononucleotide, it is then attached to AMP to form a dinucleotide
- Nicotinamide, a derivative of nicotinic acid that contains an amide rather than carboxyl group, also occurs in the diet.
- NAD+ and NADP+ serve as coenzymes in many oxidation-reduction reactions. Also a source of ADP-ribose.
- The term Nicotinic acid SHOULD NOT be confused with Nicotine.
- Nicotinic acid is a vitamin; but,
- Nicotine is the potent poison from tobacco.
Structure/Chemistry of Niacin
- Niacin is Pyridine-3-carboxylic acid.
- Niacinamide is the acid amide.
- In NAD+ or NADP+ , the reactive site is the carbon atom 4 and the nitrogen atom of the nicotinamide ring.
- The co-enzyme is bound to the apo-enzyme.
Coenzyme forms of Niacin
- Niacin is converted to its co-enzyme forms, Nicotinamide adenine dinucleotide (NAD+ ) & Nicotinamide adenine dinucleotide phosphate (NADP+).
- The niacin is attached to a ribose phosphate to form a mononucleotide.
- It is then attached to AMP, to form the dinucleotide…
FOR COMPLETE LESSON KINDLY VISIT THE VITAMINS PART IN “BIOCHEMISTRY I”. CLICK CURRICULUM TO SEE THE FULL LIST OF LESSONS.