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Metabolite Card

Note

4-Pyridoxic acid is a member of the class of compounds known as methylpyridines. More specifically it is a 2-methylpyridine derivative substituted by a hydroxy group at C-3, a carboxy group at C-4, and a hydroxymethyl group at C-5. 4-Pyridoxic acid is the catabolic product of vitamin B6 (also known as pyridoxine, pyridoxal and pyradoxamine) and is excreted in the urine. Urinary levels of 4-pyridoxic acid are lower in females than in males and will be reduced even further in persons with a riboflavin deficiency. 4-Pyridoxic acid is formed by the action of aldehyde oxidase I (an endogenous enzyme) and by microbial enzymes (pyridoxal 4-dehydrogenase), an NAD-dependent aldehyde dehydrogenase. 4-pyridoxic acid can be further broken down by the gut microflora via the enzyme known as 4-pyridoxic acid dehydrogenase. This enzyme catalyzes the four-electron oxidation of 4-pyridoxic acid to 3-hydroxy-2-methylpyridine-4,5-dicarboxylate, using nicotinamide adenine dinucleotide (NAD) as a cofactor.