Tartronic acid semialdehyde is the organic compound with the formula OCHCH(OH)CO<sub>2</sub>H. The molecule has three functional groups, aldehyde, alcohol, and carboxylic acid. A white solid, it occurs naturally. At near neutral pH, it exists as the hydrated carboxylate (HO)<sub>2</sub>CHCH(OH)CO<sub>2</sub><sup>âÂÂ</sup>, which is referred to as tartronate semialdehyde. Tartronate semialdehyde is produced and consumed on a prodigious scale as an intermediate in photorespiration, an undesirable side reaction that competes with photosynthesis. It is produced biologically by the condensation of two equivalents of glyoxylate:
This condensation is catalyzed by tartronate-semialdehyde synthase.