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A salt or ester of lactic acid (CH3CHOHCOOH). In lactates, the acidic hydrogen of the carboxyl group has been replaced by a metal or an organic radical. Lactates are optically active, with a chiral center at carbon 2. Commercial fermentation produces either the dextrorotatory (R) or the levorotatory (S) form, depending on the organism involved. See Optical activity
The R form of lactate occurs in blood and muscle as a product of glycolysis. Lack of sufficient oxygen during strenuous exercise causes enzymatic (lactate dehydrogenase) reduction of pyruvic acid to lactate, which causes tiredness, sore muscles, and even muscle cramps. During renewed oxygen supply (rest) the lactate is reoxidized to pyruvic acid and the fragments enter the Krebs (citric acid) cycle. The plasma membranes of muscle and liver are permeable to pyruvates and lactates, permitting the blood to transport them to the liver (Cori cycle). Lactates also increase during fasting and in diabetics. See Biological oxidation, Carbohydrate metabolism, Citric acid cycle
Lactates are found in certain foods (sauerkraut), and may be used for flour conditioning and in food emulsification. Alkali-metal salts act as blood coagulants and are used in calcium therapy, while esters are used as plasticizers and as solvents for lacquers. See Ester, Salt (chemistry)