Pyruvic acid

Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate (/pˈrvt/), the conjugate base, CH3COCOO, is a key 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 to fatty acids through a reaction with acetyl-CoA.[3] 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 (lactic acid fermentation).[4] 

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[5]) and another acid that Jöns Jacob Berzelius characterized the following year and named pyruvic acid.[6] Pyruvic acid is a colorless liquid with a smell similar to that of acetic acid and is miscible with water.[7] In the laboratory, pyruvic acid may be prepared by heating a mixture of tartaric acid and potassium hydrogen sulfate,[8] 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
Pyruvate is an important chemical compound in biochemistry. It is the output of the metabolism of glucose known as glycolysis.[9] One molecule of glucose breaks down into two molecules of pyruvate,[9] 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. 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 cycleor 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 (and carp[10]). 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.

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.

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
Phosphoenolpyruvate wpmp.svg Pyruvic-acid-2D-skeletal.svg
ADP ATP
Biochem reaction arrow reversible YYYY horiz med.svg
ADP ATP
pyruvate carboxylaseand PEP carboxykinase

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

]]
GlycolysisGluconeogenesis_WP534

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

pyruvate pyruvate dehydrogenase complex acetyl-CoA
Pyruvate wpmp.png Acetyl-CoA.svg
CoA +NAD+ CO2 +NADH + H+
Biochem reaction arrow forward YYNN horiz med.svg

Carboxylation by pyruvate carboxylase produces oxaloacetate.

pyruvate pyruvate carboxylase oxaloacetate
Pyruvate wpmp.png Oxaloacetate wpmp.png
ATP +CO2 ADP + Pi
Biochem reaction arrow forward YYNN horiz med.svg

Transamination by alanine transaminase produces alanine.

pyruvate alanine transaminase alanine
Pyruvate wpmp.png L-alanine-skeletal.svg
glutamate α-ketoglutarate
Biochem reaction arrow reversible YYYY horiz med.svg
glutamate α-ketoglutarate

Reduction by lactate dehydrogenase produces lactate.

pyruvate lactate dehydrogenase lactate
Pyruvate wpmp.png Lactic-acid-skeletal.svg
NADH NAD+
Biochem reaction arrow reversible YYYY horiz med.svg
NADH NAD+

Pyruvate is sold as a weight-loss supplement, though credible science has yet to back this claim. 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.[11]

There is also in vitro as well as in vivo evidence in hearts that pyruvate improves metabolism by NADH production stimulation and increases cardiac function.[12][13]

  1. ^ Jump up to: a b Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 748. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ Dawson, R. M. C.; et al. (1959). Data for Biochemical Research. Oxford: Clarendon Press.
  3. ^ Fox, Stuart Ira (2011). Human Physiology (12th ed.). McGraw=Hill. p. 146.[ISBN missing]
  4. ^ Ophardt, Charles E. “Pyruvic Acid – Cross Roads Compound”. Virtual Chembook. Elmhurst College. Retrieved April 7, 2017.
  5. ^ Thomson, Thomas (1838). “Chapter II. Of fixed acids Section”. Chemistry of organic bodies, vegetables. London: J. B. Baillière. p. 65. Retrieved December 1,2010.
  6. ^ Thorpe, Thomas Edward (1922). “Glutaric acid”. A dictionary of applied chemistry. 3. London: Longmans, Green, and Co. pp. 426–427. Retrieved December 1, 2010.
  7. ^ “Pyruvic Acid”. ChemSpider. Royal Society of Chemistry. Retrieved 21 April2017.
  8. ^ Howard, J. W.; Fraser, W. A. “Pyruvic Acid”. Organic Syntheses. 4: 63.; Collective Volume, 1, p. 475
  9. ^ Jump up to: a b 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.
  10. ^ Aren van Waarde; G. Van den Thillart; Maria Verhagen (1993). “Ethanol Formation and pH-Regulation in Fish”. Surviving Hypoxia. pp. 157–170. ISBN 0-8493-4226-0.
  11. ^ 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. 54 (1): 17–23. doi:10.1080/10408398.2011.565890. PMID 24188231.
  12. ^ Jaimes, R., III (Jul 2015). “Functional response of the isolated, perfused normoxic heart to pyruvate dehydrogenase activation by dichloroacetate and pyruvate”. Pflügers Arch. 468: 131–42. doi:10.1007/s00424-015-1717-1. PMC 4701640. PMID 26142699.
  13. ^ Hermann, H. P.; Pieske, B.; Schwarzmüller, E.; Keul, J.; Just, H.; Hasenfuss, G. (1999-04-17). “Haemodynamic effects of intracoronary pyruvate in patients with congestive heart failure: an open study”. Lancet. 353 (9161): 1321–1323. doi:10.1016/s0140-6736(98)06423-x. ISSN 0140-6736. PMID 10218531.

 

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