galactarate

Galactarate is the anionic form of galactaric acid, a six‑carbon dicarboxylic acid derived from the oxidation of galactose at both primary alcohol positions. Its chemical formula is C6H7O8− when protonated as the free acid the formula is C6H8O8. The compound can exist in several stereoisomeric forms; the most common naturally occurring forms are the D‑galactarate and L‑galactarate, corresponding to the enantiomers of the parent D‑galactaric and L‑galactaric acids.

In the biochemical context galactarate is produced during the catabolism of galactose via the Leloir pathway, where galactose is converted to galactonate and subsequently to galactarate through dehydrogenation. Some microorganisms, particularly certain bacterial strains, can further oxidize galactarate to produce glyoxal and formate. The compound also appears as a minor metabolite in plant tissues, where its presence may reflect oxidative modification of sugars under stress conditions.

Galactarate salts, such as sodium galactarate or potassium galactarate, are used in industrial settings as pH buffers and as precursors in the synthesis of pharmaceuticals and fine chemicals. In the laboratory, galactarate is occasionally employed as a reagent in carbohydrate chemistry, particularly in the synthesis of glycolipids and glycopeptides. Its solubility in water is high, and it typically displays an acidic pKa around 4.4 for the first carboxyl group and 4.9 for the second. Analytical methods for detecting galactarate include high‑performance liquid chromatography coupled with mass spectrometry, as well as enzymatic assays that measure its conversion to downstream metabolites.

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