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Pyruvic acid (CH3COCOOH) is an organic acid, a ketone, as well as the simplest of the alpha-keto acids. The carboxylate (COOH) ion (anion) of pyruvic acid, CH3COCOO−, is known as pyruvate, and is a key intersection in several metabolic pathways.
It can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or to fatty acids through acetyl-CoA. It can also be used to construct the amino acid alanine and be converted into ethanol.
It supplies energy to living 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) and another acid which
Jöns Jacob Berzelius characterized the following year and named pyruvic acid. 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, 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:
:CH
3COCl + KCN → CH
3COCN + KCl
:CH
3COCN → CH
3COCOOH
Biochemistry
Pyruvate is an important
chemical compound in
biochemistry. It is the output of the anaerobic metabolism of
glucose known as
glycolysis. One molecule of
glucose breaks down into two molecules of pyruvate, 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. Pyruvate is also converted to
oxaloacetate by an
anaplerotic reaction which replenishes
Krebs cycle intermediates; alternatively, 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 called the
citric 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 anaerobic respiration 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.
, comparing blood content of pyruvate (shown in violet near middle) with other constituents.]]
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 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.
Pyruvate decarboxylation to acetyl CoA
Pyruvate decarboxylation by the
pyruvate dehydrogenase complex produces
acetyl-CoA.
Pyruvate carboxylation to oxaloacetate
Carboxylation by the
pyruvate carboxylase produces
oxaloacetate.
Transamination by the alanine aminotransferase
Reduction to lactic acid
Reduction by the
lactate dehydrogenase produces
lactic acid.
Interactive pathway map
Origin of life
Current evolutionary theory on the
origin of life posits that the first organisms were anaerobic because the atmosphere of prebiotic Earth was, in theory, almost barren of diatomic oxygen. As such, requisite biochemical materials must have preceded life. In vitro,
iron sulfide at sufficient pressure and temperature
catalyzes the formation of pyruvate. Thus, argues
Günter Wächtershäuser, the mixing of iron-rich crust with hydrothermal vent fluid is suspected of providing the fertile basis for the formation of life.
See also
Pyruvate scale
Notes
References
Category:Keto acids
Category:Cellular respiration
Category:Exercise physiology
