lecithin

Traditional term for 1,2-diacyl-sn-glycero-3-phosphocholines or 3-sn-phosphatidylcholines, phospholipids that on hydrolysis yield two fatty acid molecules and a molecule each of glycerophosphoric acid and choline. In some varieties of l., both fatty acid s are saturated, others contain only unsaturated acids ( e.g., oleic, linoleic, or arachidonic acid); in others again, one fatty acid is saturated, the other unsaturated. Lecithins are yellowish or brown waxy substances, readily miscible in water, in which they appear under the microscope as irregular elongated particles known as “myelin forms,” and are found in nervous tissue, especially in the myelin sheaths, in egg yolk, and as essential constituents of animal and vegetable cells. [G. lekithos, egg yolk]

- l. acyltransferase SYN: l.-cholesterol acyltransferase.

- l.-cholesterol transferase a plasma enzyme that catalyzes the uptake of cholesterol esters by intermediate-density lipoproteins formed by high density lipoproteins.

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lec·i·thin 'les-ə-thən n any of several waxy hygroscopic phospholipids in which phosphatidic acid has formed an ester with choline and which are widely distributed in animals and plants, form colloidal solutions in water, and have emulsifying, wetting, and antioxidant properties also a mixture of or a substance rich in lecithins called also phosphatidylcholine

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n.

one of a group of phospholipid that are important constituents of cell membranes and are involved in the metabolism of fat by the liver. An example is phosphatidylcholine. Lecithins are present in the surfactant that occurs in fetal lung tissue. The lecithin-sphingomyelin ratio (LS ratio) is used as a measure of fetal lung maturity; an LS ratio below 2 indicates a higher risk of respiratory distress syndrome (RDS). In such cases cortisone may be given to stimulate fetal lung maturity and hence reduce the risk of RDS in the newborn.

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lec·i·thin (lesґĭ-thin) phosphatidylcholine.