Malate

Malic acid
Names


DL-Malic acid
Preferred IUPAC name 2-Hydroxybutanedioic acid
Other names Hydroxybutanedioic acid 2-Hydroxysuccinic acid L-Malic acid D-Malic acid (–)-Malic acid (+)-Malic acid (S)-Hydroxybutanedioic acid (R)-Hydroxybutanedioic acid
Identifiers
CAS Number	617-48-1^N 6915-15-7^N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:6650^Y
ChEMBL	ChEMBL1455497^N
ChemSpider	510^Y 83793 D-(+)-malic acid^Y 193317 L-(–)-malic acid^Y
ECHA InfoCard	100.027.293
EC Number	230-022-8
E number	E296 (preservatives)
IUPHAR/BPS	2480
KEGG	C00149^N
PubChem	525
UNII	817L1N4CKP^Y
InChI InChI=1S/C4H6O5/c5-2(4(8)9)1-3(6)7/h2,5H,1H2,(H,6,7)(H,8,9)^Y Key: BJEPYKJPYRNKOW-UHFFFAOYSA-N^Y InChI=1/C4H6O5/c5-2(4(8)9)1-3(6)7/h2,5H,1H2,(H,6,7)(H,8,9) Key: BJEPYKJPYRNKOW-UHFFFAOYAM
SMILES O=C(O)CC(O)C(=O)O
Properties
Chemical formula	C₄H₆O₅
Molar mass	134.09 g·mol⁻¹
Density	1.609 g cm⁻³
Melting point	130 °C (266 °F; 403 K)
Solubility in water	558 g/L (at 20 °C)
Acidity (pK_a)	pK_a1 = 3.40, pK_a2 = 5.20
Related compounds
Other anions	malate
Related carboxylic acids	succinic acid tartaric acid fumaric acid
Related compounds	butanol butyraldehyde crotonaldehyde sodium malate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is ^YN ?)
Infobox references

Malic acid is an organic compound with the molecular formula C₄H₆O₅. It is a dicarboxylic acid that is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L- and D-enantiomers), though only the L-isomer exists naturally. The salts and esters of malic acid are known as malates. The malate anion is an intermediate in the citric acid cycle.

L-Malic acid is the naturally occurring form, whereas a mixture of L- and D-malic acid is produced synthetically.

Malate plays an important role in biochemistry. In the C4 carbon fixation process, malate is a source of CO₂ in the Calvin cycle. In the citric acid cycle, (S)-malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions.

Malate is also synthesized by the carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential, allowing water to enter the cell and promote aperture of the stomata.

Malic acid was first isolated from apple juice by Carl Wilhelm Scheele in 1785.Antoine Lavoisier in 1787 proposed the name , which is derived from the Latin word for apple, — as is its genus name Malus. In German it is named (or Apfelsäure) after plural or singular of the fruit apple, but the salt(s) Malat(e). Malic acid contributes to the sourness of green apples. It is present in grapes and in most wines with concentrations sometimes as high as 5 g/l. It confers a tart taste to wine, although the amount decreases with increasing fruit ripeness. The taste of malic acid is very clear and pure in rhubarb, a plant for which it is the primary flavor. It is also a component of some artificial vinegar flavors, such as "salt and vinegar" flavored potato chips.

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Wikipedia