The Significance of Base-Exchange Reactions in Lipid Metabolism

Abstract

In recent years a number of investigators have studied, in vitro, the Ca²⁺-stimulated, non-energy-dependent, base-exchange incorporation of ethanolamine, choline and L-serine into corresponding phospholipids (Arienti et al., 1976). The enzymic system, which has been extensively studied in nervous structures (Arienti et al., 1970; Porcellati et al., 1971; Kanfer, 1972; Miller & Dawson, 1972; Goracci et al., 1973; Gaiti et al., 1974), produces the non net synthesis of membrane phospholipids, and is thought to play an interesting role in changing the structure of the polar head groups of membrane lipids (Gaiti et al., 1974). Kinetic data (Porcellati et al., 1971; Gaiti et al., 1974; Bjerve, 1973; Saito et al., 1975), Ca²⁺requirements (Arienti et al., 1970; Porcellati et al., 1971; Gaiti et al., 1974; Saito et al., 1975) and heat sensitivity measurements (Saito et al., 1975) strongly support the view that more than one enzyme is involved in the exchange reactions in brain (Porcellati et al., 1971; Gaiti et al., 1974; Saito et al., 1975), as proposed also for the liver system (Bjerve, 1973). Very recently, Miura & Kanfer (1976) have brilliantly succeeded in obtaining separate soluble fractions from rat brain which catalyze principally ethanolamine, choline or L-serine incorporation by base-exchange.