Lmalate

L-malate is the L enantiomer of malic acid, a chiral four-carbon dicarboxylic acid (2-hydroxybutanedioic acid). In biological systems, it is the predominant naturally occurring isomer and is typically designated as L-malate in reference to the stereochemistry at the α-hydroxyl-bearing carbon.

In metabolism, L-malate serves as an intermediate in the citric acid cycle (TCA cycle). It is formed from fumarate by fumarase and is then oxidized to oxaloacetate by malate dehydrogenase, producing NADH for the mitochondrial electron transport chain. Malate can be shuttled between the cytosol and mitochondria via the malate-aspartate shuttle, enabling transfer of reducing equivalents from the cytosol to the mitochondrion, and it participates in gluconeogenesis when oxaloacetate is converted to phosphoenolpyruvate.

Natural occurrence and uses: L-malate occurs in many fruits and plant tissues; it is particularly abundant in apples and grapes and contributes to the characteristic tartness of acidic fruits and wines. The free acid and its salts (malates) are used as flavorings and acidulants in foods and beverages. In commercial contexts, malic acid is often sold as a mixture of enantiomers; some products specify the L-enantiomer for stereospecific applications.

See also: D-malate, malic acid, malate dehydrogenase, malate shuttle.