Kinetics of the hydrolysis of phosphatidylcholine and lysophosphatidylcholine

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Abstract
An experimental technique capable of estimating as little as 10 nano-equivalents of long-chain carboxylic acids (fatty acids) has been used to study the decomposition of phospholipids. The rate of release of acids varied with the monovalent cation which was associated with the hydroxyl ion in the hydroxide used. Because the concentration of hydroxide was much greater than the concentration of phospholipid, the rate of hydrolysis was first order with respect to the phospholipid. The pseudo-first order reaction velocity constant varied as the first power of the concentration of lithium hydroxide, but as the second power of the concentration of potassium, sodium, tetramethylammonium, or tetraethylammonium, hydroxides. It is postulated that (i) lecithin and lysolecithin, in strong alkaline solution, bind lithium ions much more strongly than potassium, sodium, tetramethylammonium, or tetraethylammonium ions, and (ii) it is only this cation-phospholipid complex which is broken down by hydroxyl ions.