Reaction Process: Reactome:R-SCE-880009

D-2-Hydroxyglutaric acid

C5H8O5 (148.0371718)

In humans, D-2-hydroxyglutaric acid is formed by a hydroxyacid-oxoacid transhydrogenase whereas in bacteria it is formed by a 2-hydroxyglutarate synthase. D-2-Hydroxyglutaric acid is also formed via the normal activity of hydroxyacid-oxoacid transhydrogenase during conversion of 4-hydroxybutyrate to succinate semialdehyde. The compound can be converted to alpha-ketoglutaric acid through the action of a 2-hydroxyglutarate dehydrogenase (EC 1.1.99.2). In humans, there are two such enzymes (D2HGDH and L2HGDH). Both the D and the L stereoisomers of hydroxyglutaric acid are found in body fluids. D-2-Hydroxyglutaric acid is a biochemical hallmark of the inherited neurometabolic disorder D-2-hydroxyglutaric aciduria (OMIM: 600721) and the genetic disorder glutaric aciduria II. D-2-Hydroxyglutaric aciduria (caused by loss of D2HGDH or gain of function of IDH) is rare, with symptoms including cancer, macrocephaly, cardiomyopathy, mental retardation, hypotonia, and cortical blindness. An elevated urine level of D-2-hydroxyglutaric acid has been reported in patients with spondyloenchondrodysplasia (OMIM: 271550). D-2-Hydroxyglutaric acid can be converted to alpha-ketoglutaric acid through the action of 2-hydroxyglutarate dehydrogenase (D2HGDH). Additionally, the enzyme D-3-phosphoglycerate dehydrogenase (PHGDH) can catalyze the NADH-dependent reduction of alpha-ketoglutarate (AKG) to D-2-hydroxyglutarate (D-2HG). Nyhan et al. (1995) described 3 female patients, 2 of them sibs, who were found to have excess accumulation of D-2-hydroxyglutaric acid in the urine. The phenotype was quite variable, even among the sibs, but included mental retardation, macrocephaly with cerebral atrophy, hypotonia, seizures, and involuntary movements. One of the patients developed severe intermittent vomiting and was given a pyloromyotomy. The electroencephalogram demonstrated hypsarrhythmia. There was an increased concentration of protein in cerebrospinal fluid, an unusual finding in inborn errors of metabolism. D-2-Hydroxyglutaric acid can also be produced via gain-of-function mutations in the cytosolic and mitochondrial isoforms of isocitrate dehydrogenase (IDH). IDH is part of the TCA cycle and this compound is generated in high abundance when IDH is mutated. Since D-2-hydroxyglutaric acid is sufficiently similar in structure to 2-oxoglutarate (2OG), it is able to inhibit a range of 2OG-dependent dioxygenases, including histone lysine demethylases (KDMs) and members of the ten-eleven translocation (TET) family of 5-methylcytosine (5mC) hydroxylases. This inhibitory effect leads to alterations in the hypoxia-inducible factor (HIF)-mediated hypoxic response and alterations in gene expression through global epigenetic remodeling. The net effect is that D-2-hydroxyglutaric acid causes a cascading effect that leads genetic perturbations and malignant transformation. Depending on the circumstances, D-2-hydroxyglutaric acid can act as an oncometabolite, a neurotoxin, an acidogen, and a metabotoxin. An oncometabolite is a compound that promotes tumour growth and survival. A neurotoxin is compound that is toxic to neurons or nerual tissue. 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. As an oncometabolite, D-2-hydroxyglutaric acid is a competitive inhibitor of multiple alpha-ketoglutarate-dependent dioxygenases, including histone demethylases and the TET family of 5mC hydroxylases. As a result, high levels of 2-hydroxyglutarate lead to genome-wide histone and DNA methylation alterations, which in turn lead to mutations that ultimately cause cancer (PMID: 29038145). As a neurotoxin, D-2-hydroxyglutaric acid mediates its neurotoxicity through activation of N-methyl-D-aspartate receptors. D-2-Hydroxyglutaric acid is structurally similar to the excitatory amino acid glutamate and stimul... Tissue accumulation of high amounts of D 2 hydroxyglutaric acid is the biochemical hallmark of the inherited neurometabolic disorder D 2 hydroxyglutaric aciduria.

alpha-Ketoglutarate

C5H4O5-2 (144.00587339999998)

FADH2 dianion

C27H33N9O15P2-2 (785.1571288000001)

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FAD trianion

C27H30N9O15P2-3 (782.1336550000001)

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