glyoxylaat

Glyoxylate, the conjugate base of glyoxylic acid, is a two‑carbon alpha‑oxo carboxylate that functions as a key metabolic intermediate in certain organisms. In plants, bacteria and fungi it is produced and consumed in the glyoxylate cycle: isocitrate is cleaved by isocitrate lyase to yield succinate and glyoxylate, and glyoxylate is then condensed with acetyl‑CoA by malate synthase to form malate, enabling the net conversion of acetyl‑CoA into four‑carbon dicarboxylic acids and ultimately glucose.

In other organisms glyoxylate arises from the oxidation of glycolate and from the catabolism of hydroxyproline. Animals generally lack a complete glyoxylate cycle; detoxification of glyoxylate mainly proceeds by transamination to glycine via alanine‑glyoxylate aminotransferase (AGT). Glyoxylate can also be oxidized to oxalate, particularly in peroxisomes, a route that can contribute to oxalate accumulation under certain conditions.

Clinical relevance: accumulation of glyoxylate and its conversion to oxalate is implicated in oxalate stone formation. Primary hyperoxaluria type 1 results from deficiency or mislocalization of AGT, causing glyoxylate to be diverted toward oxalate production rather than glycine. Treatments focus on reducing oxalate production and excretion, including pyridoxine (vitamin B6) responsiveness in some cases, aggressive hydration, and therapies aimed at lowering oxalate levels.

Chemistry and biology: glyoxylate is a reactive two‑carbon aldehyde‑carboxylate that participates in multiple enzymatic reactions in peroxisomes and the cytosol, linking carbon metabolism with detoxification pathways and, in plants, with the glyoxylate cycle that supports growth on C2 compounds.