Vitamin B3 (Niacin/Nicotinic Acid)

Author: Gianpiero Pescarmona
Date: 11/01/2010


Niacin, also known as vitamin B3 or nicotinic acid, is a derivative of pyridine, with a carboxyl group (COOH) at the 3-position.

Other forms of vitamin B3 include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH2), as well as more complex amides and a variety of esters. The terms niacin, nicotinamide, and vitamin B3 are often used interchangeably to refer to any member of this family of compounds, since they have the same biochemical activity.

Food Sources

Endogenous synthesis

The liver can synthesize niacin from the essential amino acid tryptophan, requiring 60 mg of tryptophan to make one mg of niacin

Niacin Functions

Precursor of NAD and NADP

2013-03-17T19:15:25 - Eugenio Grillo

Endogenous synthesis

Vitamin B3 can be synthetized from Tryptophan in the liver, with a conversion rate of about 60 mg of Trp for 1 mg of Niacin, depending on the efficiency of the metabolic pathway.

Involved enzymes

The first step of the metabolic pathway is catalysed by Indoleamine 2,3-dyoxygenase (IDO-2,3) and Tryptophan 2,3-dyoxygenase (TDO-2,3) that are heme-containing oxygenases and so iron dependent enzymes.

Use of proton pump inhibitors related to vitamin B3 deficiency

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