MOLECULE

Glyceric acid

Glyceric acid is a colourless syrupy acid, obtained via the oxidation of glycerol. Glyceric acid is a weak 3-carbon sugar acid. Several phosphate derivatives of glyceric acid, including 2-phosphoglyceric acid, 3-phosphoglyceric acid, 2,3-bisphosphoglyceric acid, and 1,3-bisphosphoglyceric acid, are important biochemical intermediates in glycolysis. In particular, 3-phosphoglyceric acid is an important molecule for the biosynthesis of the amino acid serine, which in turn can be used in the synthesis of glycine and cysteine. Glyceric acid is not normally found in human biofluids, however high levels are secreted in the urine by patients suffering from D-glyceric aciduria, an inborn error of metabolism. It is also elevated in the serum of individuals suffering from D-glycerate anemia. A deficiency of human glycerate kinase has been shown to lead to D-glycerate acidemia/D-glyceric aciduria ( PMID: 20949620). Symptoms of the disease include progressive neurological impairment, hypotonia, seizures, failure to thrive, and metabolic acidosis. At sufficiently high levels, glyceric acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Abnormally high levels of organic acids (glyceric acid is an organic acid) in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis, the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of untreated glyceric aciduria. Many affected children with organic acidemias experience intellectual disability or delayed development. In adults, acidosis or acidemia is characterized by headaches, confusion, feeling tired, tremors, sleepiness, and seizures. Elevated values may also be due to microbial sources such as yeast (Aspergillus, Penicillium, probably Candida) or due to dietary sources containing glycerol (glycerine). Glyceric acid can be isolated from various crop plants (e.g. brassicas and pulses) and has also been found in peanuts, artichokes, tomatoes, apples, bananas, broad beans and grapes (PMID: 19621222).