Glyoxylic acid

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Glyoxylic acid
Skeletal formula of glyoxylic acid
Space-filling model of glyoxylic acid
Names
Preferred IUPAC name
Oxoacetic acid[1]
Systematic IUPAC name
Oxoethanoic acid
Other names
Glyoxylic acid[1]
2-Oxoacetic acid
Formylformic acid
Identifiers
3D model (
JSmol
)
741891
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
100.005.508 Edit this at Wikidata
EC Number
  • 206-058-5
25752
KEGG
UNII
  • InChI=1S/C2H2O3/c3-1-2(4)5/h1H,(H,4,5) checkY
    Key: HHLFWLYXYJOTON-UHFFFAOYSA-N checkY
  • InChI=1/C2H2O3/c3-1-2(4)5/h1H,(H,4,5)
    Key: HHLFWLYXYJOTON-UHFFFAOYAU
  • C(=O)C(=O)O
Properties
C2H2O3
Molar mass 74.035 g·mol−1
Density 1.384 g/mL
Melting point 80 °C (176 °F; 353 K)[4]
Boiling point 111 °C (232 °F; 384 K)
Acidity (pKa) 3.18,[2] 3.32 [3]
Related compounds
Other anions
glyoxylate
formic acid
acetic acid
glycolic acid
oxalic acid
propionic acid
pyruvic acid
Related compounds
acetaldehyde
glyoxal
glycolaldehyde
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Glyoxylic acid or oxoacetic acid is an organic compound. Together with acetic acid, glycolic acid, and oxalic acid, glyoxylic acid is one of the C2 carboxylic acids. It is a colourless solid that occurs naturally and is useful industrially.

Structure and nomenclature

The structure of glyoxylic acid is shown as having an

carbonyl rapidly converts to a geminal diol (described as the "monohydrate"). The equilibrium constant (K) is 300 for the formation of dihydroxyacetic acid at room temperature:[5] Dihydroxyacetic acid has been characterized by X-ray crystallography.[6]

In aqueous solution, this monohydrate exists in equilibrium with a hemiacylal dimer form:[7]

In isolation, the aldehyde structure has as a major

carboxyl hydrogen:[8]

The Henry's law constant of glyoxylic acid is KH = 1.09 × 104 × exp[(40.0 × 103/R) × (1/T − 1/298)].[9]

Preparations

The

amidation process in biosynthesis of several amidated peptides
.

For the historical record, glyoxylic acid was prepared from oxalic acid electrosynthetically:[10][11] in organic synthesis, lead dioxide cathodes were applied for preparing glyoxylic acid from oxalic acid in a sulfuric acid electrolyte.[12]

Hot

oxidize glyoxal
to glyoxylic; however this reaction is highly exothermic and prone to thermal runaway. In addition, oxalic acid is the main side product.

Also, ozonolysis of maleic acid is effective.[7]

Biological role

Glyoxylate is an intermediate of the glyoxylate cycle, which enables organisms, such as bacteria,[13] fungi, and plants [14] to convert fatty acids into carbohydrates. The glyoxylate cycle is also important for induction of plant defense mechanisms in response to fungi.[15] The glyoxylate cycle is initiated through the activity of isocitrate lyase, which converts isocitrate into glyoxylate and succinate. Research is being done to co-opt the pathway for a variety of uses such as the biosynthesis of succinate.[16]

In humans

Glyoxylate is produced via two pathways: through the oxidation of glycolate in peroxisomes or through the catabolism of hydroxyproline in mitochondria.[17] In the peroxisomes, glyoxylate is converted into glycine by AGT1 or into oxalate by glycolate oxidase. In the mitochondria, glyoxylate is converted into glycine by AGT2 or into glycolate by glyoxylate reductase. A small amount of glyoxylate is converted into oxalate by cytoplasmic lactate dehydrogenase.[18]

Oxalate and glyoxylate metabolism in hepatocytes. AGT1 and 2, alanine:glyoxylate aminotransferase 1 and 2; GO, glycolate oxidase; GR, glyoxylate reductase; HKGA, 4-hydroxy-2-ketoglutarate lyase; LDH, lactate dehydrogenase

In plants

In addition to being an intermediate in the glyoxylate cycle, glyoxylate is also an important intermediate in the photorespiration pathway. Photorespiration is a result of the side reaction of RuBisCO with O2 instead of CO2. While at first considered a waste of energy and resources, photorespiration has been shown to be an important method of regenerating carbon and CO2, removing toxic phosphoglycolate, and initiating defense mechanisms.[19][20] In photorespiration, glyoxylate is converted from glycolate through the activity of glycolate oxidase in the peroxisome. It is then converted into glycine through parallel actions by SGAT and GGAT, which is then transported into the mitochondria.[21][20] It has also been reported that the pyruvate dehydrogenase complex may play a role in glycolate and glyoxylate metabolism.[22]

Basic overview of photorespiration in Arabidopsis. GGAT, glyoxylate:glutamate aminotransferase; GLYK, glycerate kinase; GO, glycolate oxidase; HPR, hydroxypyruvate reductase; PGLP, phosphoglycolate phosphatase; Rubisco, RuBP carboxylase/oxygenase; SGAT, serine:glyoxylate aminotransferase; SHM, serine hydroxymethyltransferase

Disease relevance

Diabetes

Glyoxylate is thought to be a potential early marker for

alpha-oxoaldehydes. In a study, glyoxylate levels were found to be significantly increased in patients who were later diagnosed with Type II diabetes.[23]
The elevated levels were found sometimes up to three years before the diagnosis, demonstrating the potential role for glyoxylate to be an early predictive marker.

Nephrolithiasis

Glyoxylate is involved in the development of hyperoxaluria, a key cause of nephrolithiasis (commonly known as kidney stones). Glyoxylate is both a substrate and inductor of sulfate anion transporter-1 (sat-1), a gene responsible for oxalate transportation, allowing it to increase sat-1 mRNA expression and as a result oxalate efflux from the cell. The increased oxalate release allows the buildup of calcium oxalate in the urine, and thus the eventual formation of kidney stones.[18]

The disruption of glyoxylate metabolism provides an additional mechanism of hyperoxaluria development. Loss of function mutations in the HOGA1 gene leads to a loss of the 4-hydroxy-2-oxoglutarate aldolase, an enzyme in the hydroxyproline to glyoxylate pathway. The glyoxylate resulting from this pathway is normally stored away to prevent oxidation to oxalate in the cytosol. The disrupted pathway, however, causes a buildup of 4-hydroxy-2-oxoglutarate which can also be transported to the cytosol and converted into glyoxylate through a different aldolase. These glyoxylate molecules can be oxidized into oxalate increasing its concentration and causing hyperoxaluria.[17]

Reactions and uses

Glyoxylic acid is about ten times stronger an acid than acetic acid, with an acid dissociation constant of 4.7 × 10−4 (pKa = 3.32):

OCHCO2H ⇌ OCHCO
2
+ H+

With concentrated base, glyoxylic acid

hydroxyacetic acid and oxalic acid:[citation needed
]

2 OCHCO2H + H2O → HOCH2CO2H + HO2CCO2H

Glyoxylic acid gives heterocycles upon

1,2-diaminobenzene
.

Phenol derivatives

In general, glyoxylic acid undergoes an electrophilic aromatic substitution reaction with phenols, a versatile step in the synthesis of several other compounds.

The immediate product with

4-hydroxyphenylacetic acid, a precursor to the drug atenolol
.

The sequence of reactions, in which glyoxylic acid reacts with guaiacol the phenolic component followed by oxidation and decarboxylation, provides a route to vanillin as a net formylation process.[7][26][27]

Hopkins Cole reaction

Glyoxylic acid is a component of the Hopkins–Cole reaction, used to check for the presence of tryptophan in proteins.[28]

Environmental chemistry

Glyoxylic acid is one of several ketone- and aldehyde-containing carboxylic acids that together are abundant in

photochemical oxidation. Several different reaction pathways can ensue, leading to various other carboxylic acid and aldehyde products.[29]

Safety

The compound is not very toxic with an LD50 for rats of 2500 mg/kg.

See also

References

  1. ^ .
  2. ^ Dissociation Constants Of Organic Acids and Bases (600 compounds), http://zirchrom.com/organic.htm.
  3. ^ pKa Data Compiled by R. Williams, "Archived copy" (PDF). Archived from the original (PDF) on 2010-06-02. Retrieved 2010-06-02.{{cite web}}: CS1 maint: archived copy as title (link).
  4. ^ Merck Index, 11th Edition, 4394
  5. .
  6. .
  7. ^
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  10. .
  11. ^ Cohen, Julius (1920). Practical Organic Chemistry 2nd Ed (PDF). London: Macmillan and Co. Limited. pp. 102–104.
  12. .
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  17. ^ .
  18. ^ .
  19. ^ "photorespiration". Archived from the original on 2006-12-11. Retrieved 2017-03-09.
  20. ^
    PMID 22303256
    .
  21. .
  22. .
  23. ^ .
  24. .
  25. .
  26. .
  27. ^ Kamlet, Jonas; Mathieson, Olin (1953). Manufacture of vanillin and its homologues U.S. Patent 2,640,083 (PDF). U.S. Patent Office.
  28. .
  29. .