Pyruvate: Formula, Synthesis, Oxidation, Carboxylation: Definition, Structure & Uses

Definition Of Pyruvate

Pyruvate is regarded as one of the vital intermediates in quite several metabolic pathways. It is the end product of glycolysis, hence a critical element in cell respiration. Pyruvate enters the cycle that occurs in glycolysis with the cycle of citric acid and oxidative phosphorylation.

Role In Glycolysis And Cellular Respiration

• The glycolysis pathway changes one glucose into two pyruvates, generating two ATP molecules and two NADH molecules.

• Pyruvate bears importance for cell respiration because it can further be metabolised for energy formation.

Relation To Main Metabolism

• Pyruvate is a metabolic crossroad that can link carbohydrate, fat, and protein metabolic processes.

• It can be converted into acety l-CoA for the citric acid cycle or into lactic acid during anaerobic respiration.

What Is Pyruvic Acid?

Pyruvic acid is the form of the pyruvate in which it is in a protonated state (having added an H⁺).

Pyruvate Formula

Chemical Structure and Molecular Formula:

• Molecular formula C₃H₄O₃

• Chemical structure: CH₃COCOOH, (pyruvic acid), CH₃COCOO⁻(pyruvate)

Physical Properties

• State: Solid at room temperature

• Colour: Colorless to white

• Melting Point: 165°C (329°F)

• Solubility: Soluble in Water

Synthesis Of Pyruvate

The synthesis of Pyruvate involves:

Glycolysis Pathway

• Conversion to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

• Oxidation and phosphorylation to 1,3-bisphosphoglycerate.

• Conversion to 3-phosphoglycerate, 2–2-phosphoglycerate and then phosphoenolpyruvate.

• Final conversion to pyruvate.

Enzymes Involved

• Hexokinase

• Phosphofructokinase

• Pyruvate kinase

Energy Yield

• 2 molecules of ATP (net gain) per molecule of glucose

• 2 NADH molecules

Pyruvate Oxidation

The details are given below:

Link Reaction (Conversion to Acetyl-CoA)

• Pyruvate is decarboxylated and attached to CoA to produce acetyl-CoA.

• It gives NADH and CO₂.

Enzyme Complex: Pyruvate Dehydrogenase

• A multi-enzyme complex made up of E1 (pyruvate dehydrogenase), E2 (dihydrolipoyl transacetylase), and E3 (dihydrolipoyl dehydrogenase).

• It helps to convert pyruvate to acetyl-CoA.

• Important in replenishing citric acid cycle intermediates (anaplerotic reactions) and gluconeogenesis.

Pyruvate Carboxylation

• Biotin-dependent enzyme.

• Catalyses the carboxylation of pyruvate to oxaloacetate.

Pathways Involving Carboxylation

• Gluconeogenesis: synthesis of glucose from noncarbohydrate sources

• Anaplerotic reactions: replenishing citric acid cycle intermediates

Regulation Of Pyruvate Metabolism

The pyruvate metabolism is regulated by:

Allosteric Regulation

• Activators: Fructose-1,6-bisphosphate

• Inhibitors: ATP, acetyl-CoA, NADH

Hormonal Regulation

• Insulin stimulates glycolysis.

• Glucagon stimulates gluconeogenesis.

Feedback Mechanisms

• High levels of ATP inhibit glycolytic enzymes.

• High levels of ADP activate glycolytic enzymes.

ATP Yield From Glycolysis And Subsequent Pathways

The details are given below:

Glycolysis

• Net gain of 2 ATP molecules per glucose molecule.

• 2 NADH molecules per glucose molecule.

Citric Acid Cycle And Oxidative Phosphorylation

• Each acetyl-CoA produces 3 NADH, 1 FADH₂, and 1 GTP (equivalent to ATP).

• Total ATP yield from the complete oxidation of one glucose molecule: 30 - 32 ATP.

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