Dictionary:
cit·rate (sĭt'rāt') ![]() |
| 5min Related Video: citrate |
| Chemistry Dictionary: citrate |
| Veterinary Dictionary: citrate |
Any salt of citric acid. Citrate is the first intermediate of the citric acid cycle and tricarboxylic acid (TCA) cycle. It also plays an important role in fatty acid synthesis which takes place in the cytoplasm. It acts as a carrier of acetyl-CoA, the construction material for fatty acids. The movement is assisted by two enzymes, citrate-condensing enzyme, which catalyzes the condensation of the acetyl unit with oxaloacetate in the mitochondria, and citrate-cleavage enzyme (citrate lyase), which catalyzes the release of the acetyl radical in the cytoplasm of the cell.
| Wikipedia: Citrate |
A citrate can refer either to the conjugate base of citric acid, (C3H5O(COO)33−), or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.
Contents |
Since citric acid is a multifunctional acid, intermediate ions exist, hydrogen citrate ion, HC6H5O72− and dihydrogen citrate ion, H2C6H5O7−. These may form salts as well, called acid salts.
Salts of the hydrogen citrate ions are weakly acidic, while salts of the citrate ion itself (with an inert cation such as sodium ion) are weakly basic.
As a weak acid, citrate can be used as a component in buffer solutions, including the commonly used SSC 20X hybridization buffer[1]. This buffer uses sodium citrate and sodium chloride to maintain a neutral 7.0 pH. Other buffers may use a mixture of sodium citrate and citric acid - canonical buffer tables compiled for biochemical studies[2] describe solutions of citrate and acid for buffer pHs of between 3.0 and 6.2.
Citric acid can act as a mild chelating agent.
Citrate is an intermediate in the TCA (Krebs) Cycle. After the pyruvate dehydrogenase complex forms acetyl CoA, from pyruvate and five cofactors (Thiamine pyrophosphate, lipoamide, FAD, NAD+, and CoA), citrate synthase catalyzes the condensation of oxaloacetate with Acetyl CoA to form citrate. Citrate continues in the TCA cycle via aconitase with the eventual regeneration of oxaloacetate, which can combine with another molecule of acetyl CoA and continue cycling.
Citrate can also be transported out of the mitochondria and into the cytoplasm, then broken down into acetyl CoA for fatty acid synthesis. Citrate is a positive modulator of this conversion and allosterically regulates the enzyme acetyl-coa carboxylase, which is the regulating enzyme in the conversion of Acetyl CoA into malonyl CoA (the commitment step in fatty acid synthesis). In short: Citrate is transported to the cytoplasm, converted to Acetyl CoA which is converted into Malonyl CoA by the Acetyl CoA carboxylase enzyme which is allosterically modulated by citrate.
See also TCA cycle
High concentration of citrate can inhibit phosphofructokinase, the pace-maker of glycolysis.
| Citric Acid Cycle Metabolic Pathway | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Oxaloacetate | Malate | Fumarate | Succinate | Succinyl-CoA | ||||||||||||
| Acetyl-CoA | NADH + H+ | NAD+ | H2O | FADH2 | FAD | CoA + ATP(GTP) | Pi + ADP(GDP) | |||||||||
| + | H2O | NADH + H+ + CO2 | ||||||||||||||
| CoA | NAD+ | |||||||||||||||
| H2O | H2O | NAD(P)+ | NAD(P)H + H+ | CO2 | ||||||||||||
| Citrate | cis-Aconitate | Isocitrate | Oxalosuccinate | α-Ketoglutarate | ||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||||
| This article about metabolism is a stub. You can help Wikipedia by expanding it. |
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| Shopping: citrate |
| Magnesium Citrate | |
| Potassium Citrate | |
| Citric Acid; Potassium Citrate |
| Is citrate of Magnesia the same as Magnesium citrate? Read answer... | |
| What is the use of sodium acid citrate? Read answer... | |
| Is pseudomonas citrate positive? Read answer... |
| Why are many bacteria that are able to metabolize citrate not citrate positive in the citrate test? | |
| What is TCA citrate is a? | |
| What is the formula for citrate? |
Copyrights:
![]() | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more | |
![]() | Chemistry Dictionary. A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved. Read more | |
![]() | Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more | |
![]() | Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Citrate". Read more |