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|Section2= |Section4= }} 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. ==Biochemistry== L-Malic acid is the naturally occurring form, whereas a mixture of L- and D-malic acid is produced synthetically. File:L-Äpfelsäure.svg| File:D-Äpfelsäure.svg| 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「malic acid」の詳細全文を読む スポンサード リンク
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