Pyruvic acid

Pyruvic acid
Names
IUPAC name
2-oxopropanoic acid
Other names
α-ketopropionic acid; acetylformic acid; pyroracemic acid; Pyr
Identifiers
127-17-3 YesY
ChEBI CHEBI:32816 YesY
ChEMBL ChEMBL1162144 YesY
ChemSpider 1031 YesY
DrugBank DB00119 YesY
4809
Jmol 3D model Interactive image
KEGG C00022 N
PubChem 1060
UNII 8558G7RUTR YesY
Properties
C3H4O3
Molar mass 88.06 g/mol
Density 1.250 g/cm3
Melting point 11.8 °C (53.2 °F; 284.9 K)
Boiling point 165 °C (329 °F; 438 K)
Acidity (pKa) 2.50[1]
Related compounds
Other anions
pyruvate ion
ion of pyruvic acid
   
acetic acid
glyoxylic acid
oxalic acid
propionic acid
acetoacetic acid
Related compounds
propionaldehyde
glyceraldehyde
methylglyoxal
sodium pyruvate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO, is a key intermediate in several metabolic pathways.

Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or to fatty acids through a reaction with acetyl-CoA.[2] It can also be used to construct the amino acid alanine and can be converted into ethanol or lactic acid via fermentation.

Pyruvic acid supplies energy to cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactate when oxygen is lacking (fermentation).

Chemistry

In 1834, Théophile-Jules Pelouze distilled both tartaric acid (L-tartaric acid) and racemic acid (a mix of D- and L-tartaric acid) and isolated pyrotartaric acid (methyl succinic acid[3]) and another acid that Jöns Jacob Berzelius characterized the following year and named pyruvic acid.[4] Pyruvic acid is a colorless liquid with a smell similar to that of acetic acid and is miscible with water. In the laboratory, pyruvic acid may be prepared by heating a mixture of tartaric acid and potassium hydrogen sulfate,[5] by the oxidation of propylene glycol by a strong oxidizer (e.g., potassium permanganate or bleach), or by the hydrolysis of acetyl cyanide, formed by reaction of acetyl chloride with potassium cyanide:

CH3COCl + KCN → CH3COCN + KCl
CH3COCN → CH3COCOOH

Biochemistry

Pyruvate is an important chemical compound in biochemistry. It is the output of the metabolism of glucose known as glycolysis.[6] One molecule of glucose breaks down into two molecules of pyruvate,[6] which are then used to provide further energy, in one of two ways. Pyruvate is converted into acetyl-coenzyme A, which is the main input for a series of reactions known as the Krebs cycle (also known as the citric acid cycle, tricarboxylic acid cycle or, rarely, the Ashwal cycle when referring specifically to avocados). Pyruvate is also converted to oxaloacetate by an anaplerotic reaction, which replenishes Krebs cycle intermediates; also, the oxaloacetate is used for gluconeogenesis. These reactions are named after Hans Adolf Krebs, the biochemist awarded the 1953 Nobel Prize for physiology, jointly with Fritz Lipmann, for research into metabolic processes. The cycle is also known as the citric acid cycle or tricarboxylic acid cycle, because citric acid is one of the intermediate compounds formed during the reactions.

If insufficient oxygen is available, the acid is broken down anaerobically, creating lactate in animals and ethanol in plants and microorganisms. Pyruvate from glycolysis is converted by fermentation to lactate using the enzyme lactate dehydrogenase and the coenzyme NADH in lactate fermentation, or to acetaldehyde and then to ethanol in alcoholic fermentation.

Pyruvate is a key intersection in the network of metabolic pathways. Pyruvate can be converted into carbohydrates via gluconeogenesis, to fatty acids or energy through acetyl-CoA, to the amino acid alanine, and to ethanol. Therefore, it unites several key metabolic processes.

Reference ranges for blood tests, comparing blood content of pyruvate (shown in violet near middle) with other constituents.

Pyruvic acid production by glycolysis

In glycolysis, phosphoenolpyruvate (PEP) is converted to pyruvate by pyruvate kinase. This reaction is strongly exergonic and irreversible; in gluconeogenesis, it takes two enzymes, pyruvate carboxylase and PEP carboxykinase, to catalyze the reverse transformation of pyruvate to PEP.

phosphoenolpyruvate pyruvate kinase pyruvate
 
ADP ATP
ADP ATP
 
  pyruvate carboxylase and PEP carboxykinase

Compound C00074 at KEGG Pathway Database. Enzyme 2.7.1.40 at KEGG Pathway Database. Compound C00022 at KEGG Pathway Database.

Click on genes, proteins and metabolites below to link to respective articles. [§ 1]

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Glycolysis and Gluconeogenesis edit

  1. The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534".

Decarboxylation to acetyl CoA

Pyruvate decarboxylation by the pyruvate dehydrogenase complex produces acetyl-CoA.

pyruvate pyruvate dehydrogenase complex acetyl-CoA
 
CoA + NAD+ CO2 + NADH + H+
 
 

Carboxylation to oxaloacetate

Carboxylation by pyruvate carboxylase produces oxaloacetate.

pyruvate pyruvate carboxylase oxaloacetate
 
ATP + CO2 ADP + Pi
 
 

Transamination to alanine

Transamination by alanine transaminase produces alanine.

pyruvate alanine transaminase alanine
 
glutamate α-ketoglutarate
glutamate α-ketoglutarate
 
 

Reduction to lactate

Reduction by lactate dehydrogenase produces lactate.

pyruvate lactate dehydrogenase lactate
 
NADH NAD+
NADH NAD+
 
 

Uses

The pyruvic acid derivative bromopyruvic acid is being studied for potential cancer treatment applications by researchers at Johns Hopkins University in ways that would support the Warburg hypothesis on the cause(s) of cancer.

Pyruvate is sold as a weight-loss supplement, though evidence supporting this use is lacking. A systematic review of six trials found a statistically significant difference in body weight with pyruvate compared to placebo. However, all of the trials had methodological weaknesses and the magnitude of the effect was small. The review also identified adverse events associated with pyruvate such as diarrhea, bloating, gas, and increase in low-density lipoprotein (LDL) cholesterol. The authors concluded that there was insufficient evidence to support the use of pyruvate for weight loss.[7]

There is also in vitro evidence in hearts that pyruvate improves metabolism by NADH production stimulation and increases cardiac function.[8]

See also

Notes

  1. Dawson, R. M. C.; et al. (1959). Data for Biochemical Research. Oxford: Clarendon Press.
  2. Fox, Stuart Ira (2011). Human Physiology (12th ed.). McGraw=Hill. p. 146.
  3. Thomson, Thomas (1838). "Chapter II. Of fixed acids Section". Chemistry of organic bodies, vegetables. London: J. B. Baillière. p. 65. Retrieved December 1, 2010.
  4. Thorpe, Thomas Edward (1922). "Glutaric acid". A dictionary of applied chemistry 3. London: Longmans, Green, and Co. pp. 426–427. Retrieved December 1, 2010.
  5. Howard, J. W.; Fraser, W. A. "Pyruvic Acid". Org. Synth. 4: 63.; Coll. Vol. 1, p. 475
  6. 1 2 Lehninger, Albert L.; Nelson, David L.; Cox, Michael M. (2008). Principles of Biochemistry (5th ed.). New York, NY: W. H. Freeman and Company. p. 528. ISBN 978-0-7167-7108-1.
  7. Onakpoya, I.; Hunt, K.; Wider, B.; Ernst, E. (2014). "Pyruvate supplementation for weight loss: a systematic review and meta-analysis of randomized clinical trials". Crit. Rev. Food Sci. Nutr. 51 (1): 17–23. doi:10.1080/10408398.2011.565890. PMID 24188231.
  8. Jaimes, R., III (Jul 2015). "Functional response of the isolated, perfused normoxic heart to pyruvate dehydrogenase activation by dichloroacetate and pyruvate.". Pflugers Arch. doi:10.1007/s00424-015-1717-1. PMID 26142699.

References

External links

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