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Pyruvic acid

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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 an intermediate in several metabolic pathways throughout the cell.

Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or converted to fatty acids through a reaction with acetyl-CoA.[1] 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.[2]

History

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In 1834, Théophile-Jules Pelouze distilled tartaric acid and isolated glutaric acid and another unknown organic acid. Jöns Jacob Berzelius characterized this other acid the following year and named pyruvic acid because it was distilled using heat.[3][4] The correct molecular structure was deduced by the 1870s.[5]

Production

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Pyruvic acid is prepared by treating tartaric acid with acid.[6] It can also be produced by oxidation of propylene glycol by potassium permanganate or bleach. The hydrolysis of acetyl cyanide, formed by reaction of acetyl chloride with potassium cyanide, represents yet another route:[citation needed]

CH3COCN + 2 H2O → CH3COCO2H + NH3

Structure

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Pyruvic acid crystallizes as the keto acid, not the enol. The six non-hydrogen atoms are nearly coplanar. More relevant to biochemistry is the structure of the pyruvate anion. Several salts of pyruvate have been examined by X-ray crystallography. These tests confirm that pyruvate anion also exists in the keto form.[7][8]

Reactivity

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As a simple, abundant and bifunctional compound, pyruvic acid has been shown to participate in many reactions. Pyruvate reacts with amino acids to give alanine by the process called transamination:

CH3C(O)CO−2 + RCH2NH2 → CH3CH(NH2)CO−2 + RCHO

Pyruvic acid self-condenses to give zymonic acid, a cyclic dehydrated dimer:

2 CH3C(O)CO2H → (O=C)(HOC)(HC)C(CH3)(CO2H) + H2O

The dehydration can be induced by distillation of pyruvic acid.[9] Zymonic acid in turn forms a variety of derivatives in aqueous solution.[10]

Pyruvic acid is a precursor to several types of heterocycles. When treated with phenethylamine, it gives tetrahydroisoquinoline by a sequential condensation/acylation process (Bischler–Napieralski reaction). With ortho-phenylenediamine it condenses to give quinoxalines. Condensation with 4,5-diaminopyrimidine give hydroxypteridines.[11]

Biochemistry

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Pyruvate is important in biochemistry. It is the output of the metabolism of glucose known as glycolysis.[12] One molecule of glucose breaks down into two molecules of pyruvate,[12] 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 or tricarboxylic acid cycle). Pyruvate is also converted to oxaloacetate by an anaplerotic reaction, which replenishes Krebs cycle intermediates; also, the oxaloacetate is used for gluconeogenesis.[13]

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.[citation needed]

If insufficient oxygen is available, the acid is broken down anaerobically, creating lactate in animals and ethanol in plants and microorganisms (and in carp[14]). Pyruvate from glycolysis is converted by fermentation to lactate using the enzyme lactate dehydrogenase and the coenzyme NADH in lactate fermentation, or to acetaldehyde (with the enzyme pyruvate decarboxylase) and then to ethanol in alcoholic fermentation.[citation needed]

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.[15]

File:Blood values sorted by mass and molar concentration.png
Reference ranges for blood tests, comparing blood content of pyruvate (shown in violet near middle) with other constituents.

Pyruvic acid production by glycolysis

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In the last step of 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.[citation needed] Template:Enzymatic reaction Template:KEGG compound Template:KEGG enzyme Template:KEGG compound

Template:GlycolysisGluconeogenesis WP534

Decarboxylation to acetyl CoA

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Pyruvate decarboxylation by the pyruvate dehydrogenase complex produces acetyl-CoA. Template:Enzymatic Reaction

Carboxylation to oxaloacetate

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Carboxylation by pyruvate carboxylase produces oxaloacetate. Template:Enzymatic Reaction

Transamination to alanine

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Transamination by alanine transaminase produces alanine. Template:Enzymatic Reaction

Reduction to lactate

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Reduction by lactate dehydrogenase produces lactate. Template:Enzymatic Reaction

Environmental chemistry

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Pyruvic acid is an abundant carboxylic acid in secondary organic aerosols.[16]

Uses

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Aside from its major role in the functioning of living organisms, pyruvic acid is of interest as a reagent in the synthesis of specialized organic compounds as discussed above in the reactivity section.[11]

See also

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Notes

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  1. ↑ Fox, Stuart Ira (2011). Human Physiology (12th ed.). McGraw=Hill. p. 146.Template:ISBN missing
  2. ↑ Ophardt, Charles E. "Pyruvic Acid - Cross Roads Compound". Virtual Chembook. Elmhurst College. Archived from the original on July 31, 2018. Retrieved April 7, 2017.
  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. ↑ Berzelius, J. (1835). "Ueber eine neue, durch Destillation von Wein-und Traubensäure erhaltene Säure". Annalen der Pharmacie. 13 (1): 61–63. doi:10.1002/jlac.18350130109.
  5. ↑ "Pyruvic acid". Journal of the Chemical Society, Abstracts. 34: 31. 1878. doi:10.1039/CA8783400019.Berzelius, J. J. (1835). "Ueber die Destillationsproducte der Traubensäure" [About the Distillation of Grape Acid (Tartaric Acid)]. Annalen der Physik. 112 (9): 1–29. doi:10.1002/andp.18351120902.
  6. ↑ Template:OrgSynth
  7. ↑ Caro Garrido, Camila; Robeyns, Koen; Debecker, Damien P.; Luis, Patricia; Leyssens, Tom (2023). "From Liquid to Solid: Cocrystallization as an Engineering Tool for the Solidification of Pyruvic Acid". Crystals. 13 (5): 808. doi:10.3390/cryst13050808. hdl:2078.1/274837.
  8. ↑ Rach, W.; Kiel, G.; Gattow, G. (1988). "Über Chalkogenolate. 187. Untersuchungen über Salze der Pyruvinsäure 2. Kristallstruktur von Kaliumpyruvat, Neubestimmung der Struktur von Natriumpyruvat". Zeitschrift für Anorganische und Allgemeine Chemie. 563: 87–95. doi:10.1002/zaac.19885630113.
  9. ↑ Heger, Dominik; Eugene, Alexis J.; Parkin, Sean R.; Guzman, Marcelo I. (2019). "Crystal structure of zymonic acid and a redetermination of its precursor, pyruvic acid". Acta Crystallographica Section E. 75 (6): 858–862. doi:10.1107/S2056989019007072. PMC 6658982. PMID 31391982.
  10. ↑ Perkins, Russell J.; Shoemaker, Richard K.; Carpenter, Barry K.; Vaida, Veronica (2016). "Chemical Equilibria and Kinetics in Aqueous Solutions of Zymonic Acid". The Journal of Physical Chemistry A. 120 (51): 10096–10107. doi:10.1021/acs.jpca.6b10526. PMID 27991786.
  11. ↑ 11.0 11.1 Klingler, Franz Dietrich; Ebertz, Wolfgang (2000). "Oxocarboxylic Acids". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a18_313. ISBN 978-3-527-30385-4.
  12. ↑ 12.0 12.1 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.
  13. ↑ Template:Lehninger4th
  14. ↑ Aren van Waarde; G. Van den Thillart; Maria Verhagen (1993). "Ethanol Formation and pH-Regulation in Fish". Surviving Hypoxia. CRC Press. pp. 157–170. hdl:11370/3196a88e-a978-4293-8f6f-cd6876d8c428. ISBN 0-8493-4226-0.
  15. ↑ Template:Lehninger4th
  16. ↑ Guzman, Marcelo I.; Eugene, Alexis J. (2021-09-01). "Aqueous Photochemistry of 2-Oxocarboxylic Acids: Evidence, Mechanisms, and Atmospheric Impact". Molecules. 26 (17): 5278. doi:10.3390/molecules26175278. PMC 8433822. PMID 34500711.

References

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Template:Glycolysis Template:Amino acid metabolism intermediates

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