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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 A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...
, 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, u ...
through
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
, 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 o ...
s (such as glucose) via gluconeogenesis, 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, f ...
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 ...
or
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 nat ...
via fermentation. Pyruvic acid supplies energy to
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
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 prot ...
(also known as the Krebs cycle) when oxygen is present (
aerobic respiration Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...
), and alternatively ferments 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 w ...
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 and is miscible with water. In the laboratory, pyruvic acid may be prepared by heating a mixture of tartaric acid and
potassium hydrogen sulfate Potassium bisulfate/ Potassium Sulphate is an inorganic compound with the chemical formula KHSO4 and is the potassium acid salt of sulfuric acid. It is a white, water-soluble solid. Preparation More than 1 million tons were produced in 1985 as ...
, 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 ...
of
propylene glycol Propylene glycol ( IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two alcohol groups, it is classed as a diol. It ...
by a strong oxidizer (e.g., potassium permanganate or bleach), or by the hydrolysis of
acetyl cyanide Acetyl cyanide is the organic compound with the formula CH3C(O)CN. It is an acyl cyanide. Acetyl cyanide is a colorless liquid. Structure Its structure was determined through the use of electron diffraction intensities and rotational spectros ...
, 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 element ...
in
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 and ...
. It is the output of the metabolism of
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, u ...
known as
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
. One molecule of
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, u ...
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 gluconeogenesis. These reactions are named after Hans Adolf Krebs, 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." Alfr ...
for physiology, jointly with Fritz Lipmann, for research into metabolic processes. The cycle is also known as 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 prot ...
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 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 w ...
in animals and
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 ...
in plants and microorganisms (and carp). Pyruvate from glycolysis is converted by fermentation to
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 w ...
using the
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
lactate dehydrogenase and the
coenzyme A cofactor is a non- protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst (a catalyst is a substance that increases the rate of a chemical reaction). Cofactors can be considered "helper molecules" that as ...
NADH in lactate fermentation, or to
acetaldehyde Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the ...
(with the enzyme pyruvate decarboxylase) and then to
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 ...
in alcoholic fermentation. Pyruvate is a key intersection in the network of
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. Pyruvate can be converted into
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 o ...
s via gluconeogenesis, 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, f ...
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
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 ...
. Therefore, it unites several key metabolic processes.


Pyruvic acid production by glycolysis

In
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
, phosphoenolpyruvate (PEP) is converted to pyruvate by
pyruvate kinase Pyruvate kinase is the enzyme involved in the last step of glycolysis. It catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP), yielding one molecule of pyruvate and one molecule of ATP. Pyr ...
. 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 molecules


Decarboxylation to acetyl CoA

Pyruvate decarboxylation by the pyruvate dehydrogenase complex 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
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 w ...
.


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 ...
s.


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 In law, a trial is a coming together of parties to a dispute, to present information (in the form of evidence) in a tribunal, a formal setting with the authority to adjudicate claims or disputes. One form of tribunal is a court. The tribun ...
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 Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall densi ...
(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 a ...
'' as well as ''
in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and p ...
'' evidence in hearts that pyruvate improves metabolism by NADH production stimulation and increases cardiac function.


See also

*
Pyruvate scale The pyruvate scale measures pungency in onions and garlic with units of μmol/gfw (micromoles per gram fresh weight). It is named after pyruvic acid, the alpha-keto acid co-product created in the biochemical pathway that forms ''syn''-propanethial ...


Notes


References

*


External links


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