Pyruvic acid (CH₃COCOOH) is the simplest of the alpha-keto acids, with a

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxyl ...

and a

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

functional group. Pyruvate, the conjugate base, CH₃COCOO⁻, is an intermediate in several

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical ...

s throughout the cell. Pyruvic acid can be made from

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...

through glycolysis, converted back to

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ...

s (such as glucose) via

gluconeogenesis Gluconeogenesis (GNG) is a metabolic pathway that results in the generation of glucose from certain non- carbohydrate carbon substrates. It is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In verteb ...

, or to

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

s through a reaction with acetyl-CoA. It can also be used to construct the amino acid alanine and can be converted into

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...

lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natur ...

via fermentation. Pyruvic acid supplies energy to cells through the

citric acid cycle The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and prote ...

(also known as the Krebs cycle) when oxygen is present ( aerobic respiration), and alternatively

ferments Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

to produce

lactate Lactate may refer to: * Lactation, the secretion of milk from the mammary glands * Lactate, the conjugate base of lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with ...

when oxygen is lacking.

Chemistry

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. The correct molecular structure was deduced by the 1870s. Pyruvic acid is a colorless liquid with a smell similar to that of

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main componen ...

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 Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

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 A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one ele ...

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology ...

. It is the output of the metabolism of

known as glycolysis. One molecule of

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 (also known as the citric acid cycle or tricarboxylic acid cycle). Pyruvate is also converted to oxaloacetate by an

anaplerotic reaction Anaplerotic reactions, a term coined by Hans Kornberg and originating from the Greeἀνά 'up' anπληρόω 'to fill', are chemical reactions that form intermediates of a metabolic pathway. Examples of such are found in the citric acid cycle (TC ...

, which replenishes Krebs cycle intermediates; also, the oxaloacetate is used for

. These reactions are named after

Hans Adolf Krebs Sir Hans Adolf Krebs, FRS (, ; 25 August 1900 – 22 November 1981) was a German-born British biologist, physician and biochemist. He was a pioneer scientist in the study of cellular respiration, a biochemical process in living cells that ext ...

, the biochemist awarded the 1953

Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfre ...

for physiology, jointly with Fritz Lipmann, for research into metabolic processes. The cycle is also known as the

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

in animals and

in plants and microorganisms (and

carp Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...

). Pyruvate from glycolysis is converted by fermentation to

using the

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

lactate dehydrogenase and the coenzyme NADH in lactate fermentation, or to acetaldehyde (with the enzyme pyruvate decarboxylase) and then to

in alcoholic fermentation. Pyruvate is a key intersection in the network of

s. Pyruvate can be converted into

s via

, to

s or energy through acetyl-CoA, to the

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

alanine, and to

. Therefore, it unites several key metabolic processes. Blood values sorted by mass and molar concentration

Pyruvic acid production by glycolysis

In glycolysis, phosphoenolpyruvate (PEP) is converted to pyruvate by pyruvate kinase. This reaction is strongly exergonic and irreversible; in

, it takes two enzymes, pyruvate carboxylase and PEP carboxykinase, to catalyze the reverse transformation of pyruvate to PEP. Pyruvate molecules

Decarboxylation to acetyl CoA

Pyruvate decarboxylation by the

pyruvate dehydrogenase complex Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and thi ...

produces acetyl-CoA.

Carboxylation to oxaloacetate

Carboxylation by pyruvate carboxylase produces oxaloacetate.

Transamination to alanine

Transamination by alanine transaminase produces alanine.

Reduction to lactate

Reduction by lactate dehydrogenase produces

Environmental chemistry

Pyruvic acid is an abundant carboxylic acid in

secondary organic aerosol A secondary organic aerosol (SOA) is a molecule produced via oxidation over several generations of a parent organic molecule. In contrast to primary organic aerosols, which are emitted directly from the biosphere, secondary organic aerosols are eith ...

Uses

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

systematic review A systematic review is a scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from published studies on t ...

of six trials found a statistically significant difference in body weight with pyruvate compared to

placebo A placebo ( ) is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills), inert injections (like Saline (medicine), saline), sham surgery, and other procedures. In general ...

. 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. There is also ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology and ...

'' as well as '' in vivo'' evidence in hearts that pyruvate improves metabolism by NADH production stimulation and increases cardiac function.

Notes

References

External links

Pyruvic acid mass spectrum
{{DEFAULTSORT:Pyruvic Acid Alpha-keto acids Cellular respiration Exercise physiology Metabolism Glycolysis