Glyoxylate

Glyoxylate refers to the deprotonated form of glyoxylic acid (glyoxalic acid), which has the structural arrangement HOOC-CHO. In neutral form, the molecule is glyoxalic acid with formula C2H2O3; the glyoxylate anion, formed by loss of the carboxyl proton, has the formula C2HO3− and occurs in salts such as glyoxylates.

In biology, glyoxylate is an important metabolic intermediate. In plants, bacteria, and fungi, it features prominently in the glyoxylate cycle, a variation of the tricarboxylic acid (TCA) cycle that enables growth on two-carbon compounds. The cycle uses isocitrate lyase to cleave isocitrate into glyoxylate and succinate, and malate synthase to combine glyoxylate with acetyl-CoA to form malate. This pathway allows organisms to convert stored fats into carbohydrate precursors.

In animals, glyoxylate is produced during metabolism and can be detoxified by alanine-glyoxylate aminotransferase (AGXT) to form glycine. Deficiency of AGXT, as seen in primary hyperoxaluria type I, can lead to accumulation of glyoxylate and its conversion to oxalate, increasing the risk of kidney stones and other oxalate-related damage.

Chemically, glyoxylate is a reactive aldehyde and participates in various redox and condensation reactions. It exists mainly as the glyoxylate ion under physiological and aqueous conditions, with its exact speciation depending on pH. It serves as a key intermediate in metabolism and, in certain organisms, as a substrate linking energy production to biosynthesis.