Pyruvic acid

Pyruvic acid
IUPAC name	2-oxopropanoic acid
Other names	α-ketopropionic acid; acetylformic acid; pyroracemic acid; Pyr
Identifiers
CAS number	[127-17-3]
SMILES	CC(C(O)=O)=O
Properties
Molecular formula	C3H4O3
Molar mass	88.06 g/mol
Density	1.250 g/cm³
Melting point	11.8 °C
Boiling point	165 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Pyruvic acid is a three-carbon, alpha-keto acid that plays an important role in biochemical processes. It has the chemical formula CH₃COCO₂H. The carboxylate anion of pyruvic acid is known as pyruvate.

Pyruvic acid is formed as an end product of glycolysis, which breaks down glucose (a six-carbon-molecule) into pyruvate (a three-carbon molecule). This not only produces a small net gain of the universal energy storage molecule adenosine triphosphate (ATP), to power cellular function, but as part of aerobic respiration also provides pyruvate that can be converted to acetyl-CoA (acetyl coenzyme A) for the critically important citric acid cycle (also known as the Krebs cycle). In the absence of oxygen, pyruvate can be reduce to lactic acid.

intricacy

Chemistry

Carboxylic acids are organic acids characterized by the presence of one or more carboxyl groups in their molecules. A carboxyl group consists of a carbon atom attached to an oxygen atom with a double covalent bond and to a hydroxyl group by a single covalent bond. The chemical formula of the carboxyl group may be written as -C(=O)OH, -COOH, or -CO₂H. Salts and anions of carboxylic acids are called carboxylates.

Keto acids are organic acids containing a ketone functional group and a carboxylic acid group.

Common types of keto acids include:

• Alpha-keto acids, or 2-oxo acids, such as pyruvic acid have the keto group adjacent to the carboxylic acid

Pyruvic acid is a colorless liquid with a smell similar to that of acetic acid. It is miscible with water, and soluble in ethanol and diethyl ether. In the laboratory, pyruvic acid may be prepared by heating a mixture of tartaric acid and potassium hydrogen sulfate, or by the hydrolysis of acetyl cyanide, formed by reaction of acetyl chloride with potassium cyanide:

CH₃COCl + KCN → CH₃COCN

CH₃COCN → CH₃COCOOH

Biochemistry

Pyruvate is an important chemical compound in biochemistry. It is the output of the aerobic 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.

In carbohydrate catabolism (the breakdown of sugars), the citric acid cycle follows glycolysis, which breaks down glucose (a six-carbon-molecule) into pyruvate (a three-carbon molecule). In eukaryotes, pyruvate moves into the mitochondria. It is converted into acetyl-CoA (acetyl coenzyme A) and enters the citric acid cycle.

If insufficient oxygen is available, the acid is broken down anaerobically, creating lactic acid in animals and ethanol in plants. 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.

In glycolysis, the six-carbon sugar glucose (Glc) is oxidized to two molecules of pyruvic acid (Pyr), yielding a small net gain of chemical energy (ATP) to power cellular function.

Pyruvate is a key intersection in the network of metabolic pathways. Pyruvate can be converted to 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.

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

Glycolysis is a series of biochemical reactions by which one molecule of glucose (Glc) is oxidized to two molecules of pyruvic acid (Pyr) an a relatively small amount of the universal energy storage molecule adenosine triphosphate (ATP). This breakdown of the simple sugar glucose serves three principal functions:

• Generation of the high-energy molecules (ATP and NADH), which are used as cellular energy sources in both aerobic respiration (with oxygen) and anaerobic respiration (without oxygen)
• Production of pyruvate for the citric acid cycle as part of aerobic respiration
• Production of a variety of six- or three-carbon intermediate metabolites, which may be removed at various steps in the process for other cellular purposes (such as nucleotide biosynthesis).

As the foundation of both aerobic and anaerobic respiration, glycolysis is the archetype of universal metabolic processes known and occurring (with variations) in many types of cells in nearly all organisms. Glycolysis, through anaerobic respiration, is the main energy source in many prokaryotes, eukaryotic cells devoid of mitochondria (e.g., mature erythrocytes), and eukaryotic cells under low-oxygen conditions (e.g., heavily-exercising muscle or fermenting yeast). The near ubiquity of these reactions suggests harmony and connectivity among organisms and great antiquity; glycolysis may have originated with the first prokaryotes (organisms without a cell nucleus) at least 3.5 billion years ago.

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. The arrow indicating a reverse reaction in the Figure below is incorrect.

phosphoenolpyruvate	Pyruvate kinase		pyruvate
	ADP	ATP
	ADP	ATP
	Pyruvate kinase

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

Pyruvate decarboxylation to acetyl CoA

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

pyruvate	pyruvate dehydrogenase complex		acetyl-CoA
	CoA + NAD+	CO2 + NADH + H+

Pyruvate carboxylation to oxaloacetate

Carboxylation by the pyruvate carboxylase produces oxaloacetate.

pyruvate	pyruvate carboxylase		oxaloacetate
	ATP + CO2	ADP + Pi

Transamination by the alanine aminotransferase

pyruvate	Alanine transaminase		alanine
	Glutamate	α-ketoglutarate
	Glutamate	α-ketoglutarate

Reduction to lactate

Reduction by the lactate dehydrogenase produces lactate.

pyruvate	lactate dehydrogenase		lactate
	NADH	NAD+
	NADH	NAD+

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 almost devoid of oxygen. As such, requisite biochemical materials must have preceded life and recent experiments indicate that pyruvate can be synthesized abiotically. 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.

References

ISBN links support NWE through referral fees

• George D. Cody, Nabil Z. Boctor, Timothy R. Filley, Robert M. Hazen, James H. Scott, Anurag Sharma, Hatten S. Yoder Jr., "Primordial Carbonylated Iron-Sulfur Compounds and the Synthesis of Pyruvate," Science, 289 (5483) (25 August 2000) pp. 1337 - 1340. [1]

External links

• "Pyruvate in Cancer Prevention and Treatment"
• "ENERGY BLOCKER" KILLS BIG TUMORS IN RATS, research at Johns Hopkins on pyruvate
• "Latin uva grapes"

Glycolysis Metabolic Pathway

Glucose Hexokinase Glucose-6-phosphate Glucose-6-phosphate isomerase Fructose 6-phosphate 6-phosphofructokinase Fructose 1,6-bisphosphate Fructose bisphosphate aldolase Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Triosephosphate isomerase Glyceraldehyde 3-phosphate Glyceraldehyde-3-phosphate dehydrogenase ATP ADP ATP ADP NAD+ + Pi NADH + H+ + 2 NAD+ + Pi NADH + H+ 1,3-Bisphosphoglycerate Phosphoglycerate kinase 3-Phosphoglycerate Phosphoglycerate mutase 2-Phosphoglycerate Phosphopyruvate hydratase(Enolase) Phosphoenolpyruvate Pyruvate kinase Pyruvate Pyruvate dehydrogenase Acetyl-CoA ADP ATP H2O ADP ATP CoA + NAD+ NADH + H+ + CO2 2 2 2 2 2 2 ADP ATP H2O

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