Biochemistry: Niacin and the most important coenzymes

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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 Bthat 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.

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